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  • 1.
    Adler, Marlen
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Anjum, Mehreen
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Berg, Otto, G.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Computational and Systems Biology.
    Andersson, Dan I.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Sandegren, Linus
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    High Fitness Costs and Instability of Gene Duplications Reduce Rates of Evolution of New Genes by Duplication-Divergence Mechanisms2014In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 31, no 6, p. 1526-1535Article in journal (Refereed)
    Abstract [sv]

    An important mechanism for generation of new genes is by duplication-divergence of existing genes. Duplication-divergence includes several different sub-models, such as subfunctionalization where after accumulation of neutral mutations the original function is distributed between two partially functional and complementary genes, and neofunctionalization where a new function evolves in one of the duplicated copies while the old function is maintained in another copy. The likelihood of these mechanisms depends on the longevity of the duplicated state, which in turn depends on the fitness cost and genetic stability of the duplications. Here, we determined the fitness cost and stability of defined gene duplications/amplifications on a low copy number plasmid. Our experimental results show that the costs of carrying extra gene copies are substantial and that each additional kbp of DNA reduces fitness by approximately 0.15%. Furthermore, gene amplifications are highly unstable and rapidly segregate to lower copy numbers in absence of selection. Mathematical modelling shows that the fitness costs and instability strongly reduces the likelihood of both sub- and neofunctionalization, but that these effects can be off-set by positive selection for novel beneficial functions.

  • 2.
    Adolfsson, Sofia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Lack of Dosage Compensation Accompanies the Arrested Stage of Sex Chromosome Evolution in Ostriches2013In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 30, no 4, p. 806-810Article in journal (Refereed)
    Abstract [en]

    Sex chromosome evolution is usually seen as a process that, once initiated, will inevitably progress toward an advanced stage of degeneration of the nonrecombining chromosome. However, despite evidence that avian sex chromosome evolution was initiated > 100 Ma, ratite birds have been trapped in an arrested stage of sex chromosome divergence. We performed RNA sequencing of several tissues from male and female ostriches and assembled the transcriptome de novo. A total of 315 Z-linked genes fell into two categories: those that have equal expression level in the two sexes (for which Z-W recombination still occurs) and those that have a 2-fold excess of male expression (for which Z-W recombination has ceased). We suggest that failure to evolve dosage compensation has constrained sex chromosome divergence in this basal avian lineage. Our results indicate that dosage compensation is a prerequisite for, not only a consequence of, sex chromosome evolution.

  • 3.
    Amiri, H.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Molecular Evolution.
    Alsmark, U. C. M.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Molecular Evolution.
    Andersson, S. G. E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology, Molecular Evolution.
    Proliferation and deterioration of Rickettsia palindromic elements2002In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 19, no 8, p. 1234-1243Article in journal (Refereed)
    Abstract [en]

    It has been suggested that Rickettsia Palindromic Elements (RPEs) have evolved as selfish DNA that mediate protein sequence evolution by being targeted to genes that code for RNA and proteins. Here, we have examined the phylogenetic depth of two RPEs that are located close to the genes encoding elongation factors Tu (tuf) and G (fus) in Rickettsia. An exceptional organization of the elongation factor genes was found in all 11 species examined, with complete or partial RPEs identified downstream of the tuf gene (RPE-tuf) in six species and of the fus gene (RPE-fus) in 10 species. A phylogenetic reconstruction shows that both RPE-tuf and RPE-fus have evolved in a manner that is consistent with the expected species divergence. The analysis provides evidence for independent loss of RPE-tuf in several species, possibly mediated by short repetitive sequences flanking the site of excision. The remaining RPE-tuf sequences evolve as neutral sequences in different stages of deterioration. Likewise, highly fragmented remnants of the RPE-fus sequence were identified in two species. This suggests that genome-specific differences in the content of RPEs are the result of recent loss rather than recent proliferation.

  • 4.
    Andersson, Jan O
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Molecular Evolution.
    Andersson, Siv GE
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Molecular Evolution.
    Genome degradation is an ongoing process in Rickettsia1999In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, ISSN 0737-403, Vol. 16, no 9, p. 1178-1191Article in journal (Other academic)
    Abstract [en]

    To study reductive evolutionary processes in bacterial genomes, we examine sequences in the Rickettsia genomes which are unconstrained by selection and evolve as pseudogenes, one of which is the metK gene, which codes for AdoMet synthetase. Here, we sequenced the metK gene and three surrounding genes in eight different species of the genus Rickettsia. The metK gene was found to contain a high incidence of deletions in six lineages, while the three genes in its surroundings were functionally conserved in all eight lineages. A more drastic example of gene degradation was identified in the metK downstream region, which contained an open reading frame in Rickettsia felis. Remnants of this open reading frame could be reconstructed in five additional species by eliminating sites of frameshift mutations and termination codons. A detailed examination of the two reconstructed genes revealed that deletions strongly predominate over insertions and that there is a strong transition bias for point mutations which is coupled to an excess of GC-to-AT substitutions. Since the molecular evolution of these inactive genes should reflect the rates and patterns of neutral mutations, our results strongly suggest that there is a high spontaneous rate of deletions as well as a strong mutation bias toward AT pairs in the Rickettsia genomes. This may explain the low genomic G + C content (29%), the small genome size (1.1 Mb), and the high noncoding content (24%), as well as the presence of several pseudogenes in the Rickettsia prowazekii genome.

  • 5.
    Andersson, Jan O
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology.
    Andersson, Siv GE
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology.
    Pseudogenes, junk DNA, and the dynamics of Rickettsia genomes2001In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 18, no 5, p. 829-839Article in journal (Refereed)
    Abstract [en]

    Studies of neutrally evolving sequences suggest that differences in eukaryotic genome sizes result from different rates of DNA loss. However, very few pseudogenes have been identified in microbial species, and the processes whereby genes and genomes deteriorate in bacteria remain largely unresolved. The typhus-causing agent, Rickettsia prowazekii, is exceptional in that as much as 24% of its 1.1-Mb genome consists of noncoding DNA and pseudogenes. To test the hypothesis that the noncoding DNA in the R. prowazekii genome represents degraded remnants of ancestral genes, we systematically examined all of the identified pseudogenes and their flanking sequences in three additional Rickettsia species. Consistent with the hypothesis, we observe sequence similarities between genes and pseudogenes in one species and intergenic DNA in another species. We show that the frequencies and average sizes of deletions are larger than insertions in neutrally evolving pseudogene sequences. Our results suggest that inactivated genetic material in the Rickettsia genomes deteriorates spontaneously due to a mutation bias for deletions and that the noncoding sequences represent DNA in the final stages of this degenerative process.

  • 6.
    Atkinson, Gemma
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organism Biology, Systematic Biology.
    Baldauf, Sandra
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organism Biology, Systematic Biology.
    Evolution of elongation factor G and the origins of mitochondrial and chloroplast forms2011In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 28, no 3, p. 1281-1292Article in journal (Refereed)
    Abstract [en]

    Protein synthesis elongation factor G (EF-G) is an essential protein with central roles in both the elongation and ribosome recycling phases of protein synthesis. Although EF-G evolution is predicted to be conservative, recent reports suggest otherwise. We have characterized EF-G in terms of its molecular phylogeny, genomic context and patterns of amino acid substitution. We find that most bacteria carry a single "canonical" EF-G, which is phylogenetically conservative and encoded in an str operon. However, we also find a number of EF-G paralogs. These include a pair of EF-Gs that are mostly found together and in an eclectic subset of bacteria, specifically delta-proteobacteria, spirochaetes and planctomycetes (the "spd" bacteria). These spdEFGs have also given rise to the mitochondrial factors mtEFG1 and mtEFG2, which probably arrived in eukaryotes before the eukaryotic last common ancestor. Meanwhile, chloroplasts apparently use an α-proteobacterial derived EF-G, rather than the expected cyanobacterial form. The long-term co-maintenance of the spd/mtEFGs may be related to their subfunctionalization for translocation and ribosome recycling. Consistent with this, patterns of sequence conservation and site-specific evolutionary rate shifts suggest that the faster evolving spd/mtEFG2 has lost translocation function, but, surprisingly, the protein also shows little conservation of sites related to recycling activity. On the other hand, spd/mtEFG1, although more slowly evolving, shows signs of substantial remodeling. This is particularly extensive in the GTPase domain, including a highly conserved three amino acid insertion in switch I. We suggest that sub-functionalization of the spd/mtEFGs is not a simple case of specialization for subsets of original activities. Rather the duplication allows the release of one paralog from the selective constraints imposed by dual functionality thus allowing it to become more highly specialized. Thus the potential for fine-tuning afforded by subfunctionalization may explain the maintenance of EF-G paralogs.

  • 7.
    Axelsson, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolutionary Biology. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Quantification of Adaptive Evolution of Genes Expressed in Avian Brain and the Population Size Effect on the Efficacy of Selection2009In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 26, no 5, p. 1073-1079Article in journal (Refereed)
    Abstract [en]

    Whether protein evolution is mainly due to fixation of beneficial alleles by positive selection or to random genetic drift has remained a contentious issue over the years. Here, we use two genomewide polymorphism data sets collected from chicken populations, together with divergence data from >5,000 chicken-zebra finch gene orthologs expressed in brain, to assess the amount of adaptive evolution in protein-coding genes of birds. First, we show that estimates of the fixation index (FI, the ratio of fixed nonsynonymous-to-synonymous changes over the ratio of the corresponding polymorphisms) are highly dependent on the character of the underlying data sets. Second, by using polymorphism data from high-frequency alleles, to avoid the confounding effect of slightly deleterious mutations segregating at low frequency, we estimate that about 20% of amino acid changes have been brought to fixation through positive selection during avian evolution. This estimate is intermediate to that obtained in humans (lower) and flies as well as bacteria (higher), and is consistent with population genetics theory that stipulates a positive relationship between the efficiency of selection and the effective population size. Further, by comparing the FIs for common and all alleles, we estimate that approximate to 20% of nonsynonymous variation segregating in chicken populations represent slightly deleterious mutations, which is less than in Drosophila. Overall, these results highlight the link between the effective population size and positive as well as negative selection.

  • 8. Axelsson, Erik
    et al.
    Willerslev, Eske
    Gilbert, M Thomas P
    Nielsen, Rasmus
    The effect of ancient DNA damage on inferences of demographic histories.2008In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 25, no 10, p. 2181-7Article in journal (Refereed)
    Abstract [en]

    The field of ancient DNA (aDNA) is casting new light on many evolutionary questions. However, problems associated with the postmortem instability of DNA may complicate the interpretation of aDNA data. For example, in population genetic studies, the inclusion of damaged DNA may inflate estimates of diversity. In this paper, we examine the effect of DNA damage on population genetic estimates of ancestral population size. We simulate data using standard coalescent simulations that include postmortem damage and show that estimates of effective population sizes are inflated around, or right after, the sampling time of the ancestral DNA sequences. This bias leads to estimates of increasing, and then decreasing, population sizes, as observed in several recently published studies. We reanalyze a recently published data set of DNA sequences from the Bison (Bison bison/Bison priscus) and show that the signal for a change in effective population size in this data set vanishes once the effects of putative damage are removed. Our results suggest that population genetic analyses of aDNA sequences, which do not accurately account for damage, should be interpreted with great caution.

  • 9.
    Backström, Niclas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Zhang, Qu
    Edwards, Scott V.
    Evidence from a House Finch (Haemorhous mexicanus) Spleen Transcriptome for Adaptive Evolution and Biased Gene Conversion in Passerine Birds2013In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 30, no 5, p. 1046-1050Article in journal (Refereed)
    Abstract [en]

    Identifying genes influenced by natural selection can provide information about lineage-specific adaptations, and transcriptomes generated by next-generation sequencing are a useful resource for identifying such genes. Here, we utilize a spleen transcriptome for the house finch (Haemorhous mexicanus), an emerging model for sexual selection and disease ecology, together with previously sequenced avian genomes (chicken, turkey, and zebra finch), to investigate lineage-specific adaptations within birds. An analysis of 4,398 orthologous genes revealed a significantly higher ratio of nonsynonymous to synonymous substitutions and significantly higher GC content in passerines than in galliforms, an observation deviating from strictly neutral expectations but consistent with an effect of biased gene conversion on the evolutionary rate in passerines. These data also showed that genes exhibiting signs of positive selection and fast evolution in passerines have functional roles related to fat metabolism, neurodevelopment, and ion binding.

  • 10. Blum, Michael G. B.
    et al.
    Jakobsson, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Deep Divergences of Human Gene Trees and Models of Human Origins2011In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 28, no 2, p. 889-898Article in journal (Refereed)
    Abstract [en]

    Two competing hypotheses are at the forefront of the debate on modern human origins. In the first scenario, known as the recent Out-of-Africa hypothesis, modern humans arose in Africa about 100,000-200,000 years ago and spread throughout the world by replacing the local archaic human populations. By contrast, the second hypothesis posits substantial gene flow between archaic and emerging modern humans. In the last two decades, the young time estimates-between 100,000 and 200,000 years-of the most recent common ancestors for the mitochondrion and the Y chromosome provided evidence in favor of a recent African origin of modern humans. However, the presence of very old lineages for autosonnal and X-linked genes has often been claimed to be incompatible with a simple, single origin of modern humans. Through the analysis of a public DNA sequence database, we find, similar to previous estimates, that the common ancestors of autosomal and X-linked genes are indeed very old, living, on average, respectively, 1,500,000 and 1,000,000 years ago. However, contrary to previous conclusions, we find that these deep gene genealogies are consistent with the Out-of-Africa scenario provided that the ancestral effective population size was approximately 14,000 individuals. We show that an ancient bottleneck in the Middle Pleistocene, possibly arising from an ancestral structured population, can reconcile the contradictory findings from the mitochondrion on the one hand, with the autosomes and the X chromosome on the other hand.

  • 11. Bollongino, Ruth
    et al.
    Burger, Joachim
    Powell, Adam
    Mashkour, Marjan
    Vigne, Jean-Denis
    Thomas, Mark G.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Modern Taurine Cattle Descended from Small Number of Near-Eastern Founders2012In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 29, no 9, p. 2101-2104Article in journal (Refereed)
    Abstract [en]

    Archaeozoological and genetic data indicate that taurine cattle were first domesticated from local wild ox (aurochs) in the Near East some 10,500 years ago. However, while modern mitochondrial DNA (mtDNA) variation indicates early Holocene founding event(s), a lack of ancient DNA data from the region of origin, variation in mutation rate estimates, and limited application of appropriate inference methodologies have resulted in uncertainty on the number of animals first domesticated. A large number would be expected if cattle domestication was a technologically straightforward and unexacting region-wide phenomenon, while a smaller number would be consistent with a more complex and challenging process. We report mtDNA sequences from 15 Neolithic to Iron Age Iranian domestic cattle and, in conjunction with modern data, use serial coalescent simulation and approximate Bayesian computation to estimate that around 80 female aurochs were initially domesticated. Such a low number is consistent with archaeological data indicating that initial domestication took place in a restricted area and suggests the process was constrained by the difficulty of sustained managing and breeding of the wild progenitors of domestic cattle.

  • 12.
    Bolívar, Paulina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Mugal, Carina F
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Nater, Alexander
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Recombination Rate Variation Modulates Gene Sequence Evolution Mainly via GC-Biased Gene Conversion, Not Hill-Robertson Interference, in an Avian System2016In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 33, no 1, p. 216-227Article in journal (Refereed)
    Abstract [en]

    The ratio of nonsynonymous to synonymous substitution rates (ω) is often used to measure the strength of natural selection. However, ω may be influenced by linkage among different targets of selection, that is, Hill-Robertson interference (HRI), which reduces the efficacy of selection. Recombination modulates the extent of HRI but may also affect ω by means of GC-biased gene conversion (gBGC), a process leading to a preferential fixation of G:C ("strong," S) over A:T ("weak," W) alleles. As HRI and gBGC can have opposing effects on ω, it is essential to understand their relative impact to make proper inferences of ω. We used a model that separately estimated S-to-S, S-to-W, W-to-S, and W-to-W substitution rates in 8,423 avian genes in the Ficedula flycatcher lineage. We found that the W-to-S substitution rate was positively, and the S-to-W rate negatively, correlated with recombination rate, in accordance with gBGC but not predicted by HRI. The W-to-S rate further showed the strongest impact on both dN and dS. However, since the effects were stronger at 4-fold than at 0-fold degenerated sites, likely because the GC content of these sites is farther away from its equilibrium, ω slightly decreases with increasing recombination rate, which could falsely be interpreted as a consequence of HRI. We corroborated this hypothesis analytically and demonstrate that under particular conditions, ω can decrease with increasing recombination rate. Analyses of the site-frequency spectrum showed that W-to-S mutations were skewed toward high, and S-to-W mutations toward low, frequencies, consistent with a prevalent gBGC-driven fixation bias.

  • 13.
    Brandström, Mikael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Evolutionary Biology.
    Bagshaw, Andrew T.
    Gemmell, Neil J.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Evolutionary Biology.
    The relationship between microsatellite polymorphism and recombination hot spots in the human genome2008In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 25, no 12, p. 2579-2587Article in journal (Refereed)
    Abstract [en]

    Although previous studies have failed to detect an association between microsatellite polymorphism and broadscale recombination rates in the human genome, there are several possible reasons why such a relationship could exist. For instance, there might be a direct link if recombination is mutagenic to microsatellite sequences or if polymorphic microsatellites act as recombination signals. Alternatively, recombination could exert an indirect effect by uncoupling of natural selection at linked loci, promoting polymorphism. As recombination is concentrated in narrow hotspot regions in the human genome, we investigated the relationship between microsatellite polymorphism and recombination hot spots. By using data from a common allele frequency database, we found several polymorphism estimates to be similar for hot spots and the genomic average. However, this is likely explained by an ascertainment bias because markers with high polymorphism information content are usually selected for genotyping in human populations and pedigrees. In contrast, by using an unbiased set of shotgun sequence data, we found an excess of microsatellite polymorphism in recombination hot spots of 14%. However, when other genomic variables are taken into account in a generalized model and using wavelet analysis, the effect is no longer detectable and the only firm predictor of microsatellite polymorphism is the incidence of SNPs and indels. One possible neutral explanation to these observations is that there is a common denominator affecting the local rate of mutation in unique as well as in repetitive DNA, for example, base composition.

  • 14.
    Brindefalk, Björn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Molecular Evolution.
    Viklund, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Molecular Evolution.
    Larsson, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Molecular Evolution.
    Thollesson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Molecular Evolution.
    Andersson, Siv G.E.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Molecular Evolution.
    Origin and evolution of the mitochondrial aminoacyl-tRNA synthetases2007In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 24, no 3, p. 743-756Article in journal (Refereed)
    Abstract [en]

    Many theories favor a fusion of 2 prokaryotic genomes for the origin of the Eukaryotes, but there are disagreements on the origin, timing, and cellular structures of the cells involved. Equally controversial is the source of the nuclear genes for mitochondrial proteins, although the α-proteobacterial contribution to the mitochondrial genome is well established. Phylogenetic inferences show that the nuclearly encoded mitochondrial aminoacyl-tRNA synthetases (aaRSs) occupy a position in the tree that is not close to any of the currently sequenced α-proteobacterial genomes, despite cohesive and remarkably well-resolved α-proteobacterial clades in 12 of the 20 trees. Two or more α-proteobacterial clusters were observed in 8 cases, indicative of differential loss of paralogous genes or horizontal gene transfer. Replacement and retargeting events within the nuclear genomes of the Eukaryotes was indicated in 10 trees, 4 of which also show split α-proteobacterial groups. A majority of the mitochondrial aaRSs originate from within the bacterial domain, but none specifically from the α-Proteobacteria. For some aaRS, the endosymbiotic origin may have been erased by ongoing gene replacements on the bacterial as well as the eukaryotic side. For others that accurately resolve the α-proteobacterial divergence patterns, the lack of affiliation with mitochondria is more surprising. We hypothesize that the ancestral eukaryotic gene pool hosted primordial "bacterial-like" genes, to which a limited set of α-proteobacterial genes, mostly coding for components of the respiratory chain complexes, were added and selectively maintained.

  • 15.
    Burri, Reto
    et al.
    Laboratory for Conservation Biology, Department of Ecology and Evolution, Biophore, University of Lausanne, Lausanne, Switzerland .
    Hirzel, Hélène Niculita
    Salamin, Nicolas
    Roulin, Alexandre
    Fumagalli, Luca
    Evolutionary patterns of MHC class II B in owls and their implications for the understanding of avian MHC evolution2008In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 25, no 6, p. 1180-1191Article in journal (Refereed)
    Abstract [en]

    Owing to its special mode of evolution and central role in the adaptive immune system, the major histocompatibility complex (MHC) has become the focus of diverse disciplines such as immunology, evolutionary ecology, and molecular evolution. MHC evolution has been studied extensively in diverse vertebrate lineages over the last few decades, and it has been suggested that birds differ from the established mammalian norm. Mammalian MHC genes evolve independently, and duplication history (i.e., orthology) can usually be traced back within lineages. In birds, this has been observed in only 3 pairs of closely related species. Here we report strong evidence for the persistence of orthology of MHC genes throughout an entire avian order. Phylogenetic reconstructions of MHC class II B genes in 14 species of owls trace back orthology over tens of thousands of years in exon 3. Moreover, exon 2 sequences from several species show closer relationships than sequences within species, resembling transspecies evolution typically observed in mammals. Thus, although previous studies suggested that long-term evolutionary dynamics of the avian MHC was characterized by high rates of concerted evolution, resulting in rapid masking of orthology, our results question the generality of this conclusion. The owl MHC thus opens new perspectives for a more comprehensive understanding of avian MHC evolution.

  • 16.
    Burri, Reto
    et al.
    Laboratory for Conservation Biology, Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland .
    Salamin, Nicolas
    Studer, Romain A
    Roulin, Alexandre
    Fumagalli, Luca
    Adaptive divergence of ancient gene duplicates in the avian MHC class II beta2010In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 27, no 10, p. 2360-2374Article in journal (Refereed)
    Abstract [en]

    Gene duplication and neofunctionalization are known to be important processes in the evolution of phenotypic complexity. They account for important evolutionary novelties that confer ecological adaptation, such as the major histocompatibility complex (MHC), a multigene family crucial to the vertebrate immune system. In birds, two MHC class II β (MHCIIβ) exon 3 lineages have been recently characterized, and two hypotheses for the evolutionary history of MHCIIβ lineages were proposed. These lineages could have arisen either by 1) an ancient duplication and subsequent divergence of one paralog or by 2) recent parallel duplications followed by functional convergence. Here, we compiled a data set consisting of 63 MHCIIβ exon 3 sequences from six avian orders to distinguish between these hypotheses and to understand the role of selection in the divergent evolution of the two avian MHCIIβ lineages. Based on phylogenetic reconstructions and simulations, we show that a unique duplication event preceding the major avian radiations gave rise to two ancestral MHCIIβ lineages that were each likely lost once later during avian evolution. Maximum likelihood estimation shows that following the ancestral duplication, positive selection drove a radical shift from basic to acidic amino acid composition of a protein domain facing the α-chain in the MHCII α β-heterodimer. Structural analyses of the MHCII α β-heterodimer highlight that three of these residues are potentially involved in direct interactions with the α-chain, suggesting that the shift following duplication may have been accompanied by coevolution of the interacting α- and β-chains. These results provide new insights into the long-term evolutionary relationships among avian MHC genes and open interesting perspectives for comparative and population genomic studies of avian MHC evolution.

  • 17.
    Canbäck, Björn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Molecular Evolution.
    Tamas, Ivica
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Molecular Evolution.
    Andersson, Siv
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Molecular Evolution.
    A phylogenomic study of endosymbiotic bacteria2004In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 21, no 6, p. 1110-1122Article in journal (Refereed)
    Abstract [en]

    Endosymbiotic bacteria of aphids, Buchnera aphidicola, and tsetse flies, Wigglesworthia glossinidia, are descendents of free-living γ-Proteobacteria. The acceleration of sequence evolution in the endosymbiont genomes is here estimated from a phylogenomic analysis of the γ-Proteobacteria. The tree topologies associated with the most highly conserved genes suggest that the endosymbionts form a sister group with Escherichia coli, Salmonella sp., and Yersinia pestis. Our results indicate that deviant tree topologies result from high substitution rates and biased nucleotide patterns, rather than from lateral gene transfer, as previously suggested. A reinvestigation of the relative rate increase in the endosymbiont genomes reveals variability among genes that correlate with host-associated metabolic dependencies. The conclusion is that host-level selection has retarded both the loss of genes and the acceleration of sequence evolution in endocellular symbionts.

  • 18.
    Chen, Jun
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Glemin, Sylvain
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab. Univ Montpellier, CNRS, IRD, Inst Sci Evolut,EPHE,UMR 5554, Montpellier, France..
    Lascoux, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Genetic Diversity and the Efficacy of Purifying Selection across Plant and Animal Species2017In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 34, no 6, p. 1417-1428Article in journal (Refereed)
    Abstract [en]

    A central question in evolutionary biology is why some species have more genetic diversity than others and a no less important question is why selection efficacy varies among species. Although these questions have started to be tackled in animals, they have not been addressed to the same extent in plants. Here, we estimated nucleotide diversity at synonymous, pi(S), and nonsynonymous sites, pi(N), and a measure of the efficacy of selection, the ratio pi(N)/pi(S), in 34 animal and 28 plant species using full genome data. We then evaluated the relationship of nucleotide diversity and selection efficacy with effective population size, the distribution of fitness effect and life history traits. In animals, our data confirm that longevity and propagule size are the variables that best explain the variation in pi(S) among species. In plants longevity also plays a major role as well as mating system. As predicted by the nearly neutral theory of molecular evolution, the log of pi(N)/pi(S) decreased linearly with the log of pi(S) but the slope was weaker in plants than in animals. This appears to be due to a higher mutation rate in long lived plants, and the difference disappears when pi(S) is rescaled by the mutation rate. Differences in the distribution of fitness effect of new mutations also contributed to variation in pi(N)/pi(S) among species.

  • 19.
    Cheng, R. R.
    et al.
    Rice Univ, Ctr Theoret Biol Phys, Houston, TX 77005 USA..
    Nordesjö, O.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology.
    Hayes, R. L.
    Univ Michigan, Dept Biophys, Ann Arbor, MI 48109 USA..
    Levine, H.
    Rice Univ, Ctr Theoret Biol Phys, Houston, TX 77005 USA.;Rice Univ, Dept Bioengn, Houston, TX USA..
    Flores, S. C.
    Uppsala Univ, Dept Cell & Mol Biol, Uppsala, Sweden..
    Onuchic, J. N.
    Rice Univ, Ctr Theoret Biol Phys, Houston, TX 77005 USA.;Rice Univ, Dept Phys & Astron, Houston, TX 77005 USA.;Rice Univ, Dept Chem & Biosci, Houston, TX 77005 USA..
    Morcos, F.
    Univ Texas Dallas, Dept Biol Sci, Dallas, TX 75080 USA.;Univ Texas Dallas, Ctr Syst Biol, Dallas, TX 75080 USA..
    Connecting the Sequence-Space of Bacterial Signaling Proteins to Phenotypes Using Coevolutionary Landscapes2016In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 33, no 12, p. 3054-3064Article in journal (Refereed)
    Abstract [en]

    Two-component signaling (TCS) is the primary means by which bacteria sense and respond to the environment. TCS involves two partner proteins working in tandem, which interact to perform cellular functions whereas limiting interactions with non-partners (i.e., cross-talk). We construct a Potts model for TCS that can quantitatively predict how mutating amino acid identities affect the interaction between TCS partners and non-partners. The parameters of this model are inferred directly from protein sequence data. This approach drastically reduces the computational complexity of exploring the sequence-space of TCS proteins. As a stringent test, we compare its predictions to a recent comprehensive mutational study, which characterized the functionality of 20 4 mutational variants of the PhoQ kinase in Escherichia coli. We find that our best predictions accurately reproduce the amino acid combinations found in experiment, which enable functional signaling with its partner PhoP. These predictions demonstrate the evolutionary pressure to preserve the interaction between TCS partners as well as prevent unwanted cross-talk. Further, we calculate the mutational change in the binding affinity between PhoQ and PhoP, providing an estimate to the amount of destabilization needed to disrupt TCS.

  • 20. Cruz, F.
    et al.
    Vilà, C.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Evolutionary Biology.
    Webster, Matthew T.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    The legacy of domestication: Accumulation of deleterious mutations in the dog genome2008In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 25, no 11, p. 2331-2336Article in journal (Refereed)
    Abstract [en]

    Dogs exhibit more phenotypic variation than any other mammal and are affected by a wide variety of genetic diseases. However, the origin and genetic basis of this variation is still poorly understood. We examined the effect of domestication on the dog genome by comparison with its wild ancestor, the gray wolf. We compared variation in dog and wolf genes using whole-genome single nucleotide polymorphism (SNP) data. The d(N)/d(S) ratio (omega) was around 50% greater for SNPs found in dogs than in wolves, indicating that a higher proportion of nonsynonymous alleles segregate in dogs compared with nonfunctional genetic variation. We suggest that the majority of these alleles are slightly deleterious and that two main factors may have contributed to their increase. The first is a relaxation of selective constraint due to a population bottleneck and altered breeding patterns accompanying domestication. The second is a reduction of effective population size at loci linked to those under positive selection due to Hill-Robertson interference. An increase in slightly deleterious genetic variation could contribute to the prevalence of disease in modern dog breeds.

  • 21. Dalen, Love
    et al.
    Orlando, Ludovic
    Shapiro, Beth
    Brandstrom-Durling, Mikael
    Quam, Rolf
    Gilbert, M. Thomas P.
    Diez Fernandez-Lomana, J. Carlos
    Willerslev, Eske
    Luis Arsuaga, Juan
    Götherström, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Partial Genetic Turnover in Neandertals: Continuity in the East and Population Replacement in the West2012In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 29, no 8, p. 1893-1897Article in journal (Refereed)
    Abstract [en]

    Remarkably little is known about the population-level processes leading up to the extinction of the neandertal. To examine this, we use mitochondrial DNA sequences from 13 neandertal individuals, including a novel sequence from northern Spain, to examine neandertal demographic history. Our analyses indicate that recent western European neandertals (< 48 kyr) constitute a tightly defined group with low mitochondrial genetic variation in comparison with both eastern and older (> 48 kyr) European neandertals. Using control region sequences, Bayesian demographic simulations provide higher support for a model of population fragmentation followed by separate demographic trajectories in subpopulations over a null model of a single stable population. The most parsimonious explanation for these results is that of a population turnover in western Europe during early Marine Isotope Stage 3, predating the arrival of anatomically modern humans in the region.

  • 22. Dutilh, Bas E.
    et al.
    Snel, Berend
    Ettema, Thijs J.G.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution.
    Huynen, Martijn A.
    Signature genes as a phylogenomic tool2008In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 25, no 8, p. 1659-1667Article in journal (Refereed)
    Abstract [en]

    Gene content has been shown to contain a strong phylogenetic signal, yet its usage for phylogenetic questions is hampered by horizontal gene transfer and parallel gene loss and until now required completely sequenced genomes. Here, we introduce an approach that allows the phylogenetic signal in gene content to be applied to any set of sequences, using signature genes for phylogenetic classification. The hundreds of publicly available genomes allow us to identify signature genes at various taxonomic depths, and we show how the presence of signature genes in an unspecified sample can be used to characterize its taxonomic composition. We identify 8,362 signature genes specific for 112 prokaryotic taxa. We show that these signature genes can be used to address phylogenetic questions on the basis of gene content in cases where classic gene content or sequence analyses provide an ambiguous answer, such as for Nanoarchaeum equitans, and even in cases where complete genomes are not available, such as for metagenomics data. Cross-validation experiments leaving out up to 30% of the species show that approximately 92% of the signature genes correctly place the species in a related clade. Analyses of metagenomics data sets with the signature gene approach are in good agreement with the previously reported species distributions based on phylogenetic analysis of marker genes. Summarizing, signature genes can complement traditional sequence-based methods in addressing taxonomic questions.

  • 23.
    Figuet, Emeric
    et al.
    Univ Montpellier, CNRS, Inst Sci Evolut, IRD,EPHE,UMR 5554, F-34059 Montpellier, France..
    Nabholz, Benoit
    Univ Montpellier, CNRS, Inst Sci Evolut, IRD,EPHE,UMR 5554, F-34059 Montpellier, France..
    Bonneau, Manon
    Univ Montpellier, CNRS, Inst Sci Evolut, IRD,EPHE,UMR 5554, F-34059 Montpellier, France..
    Carrio, Eduard Mas
    Univ Montpellier, CNRS, Inst Sci Evolut, IRD,EPHE,UMR 5554, F-34059 Montpellier, France..
    Nadachowska-Brzyska, Krystyna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Galtier, Nicolas
    Univ Montpellier, CNRS, Inst Sci Evolut, IRD,EPHE,UMR 5554, F-34059 Montpellier, France..
    Life History Traits, Protein Evolution, and the Nearly Neutral Theory in Amniotes2016In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 33, no 6, p. 1517-1527Article in journal (Refereed)
    Abstract [en]

    The nearly neutral theory of molecular evolution predicts that small populations should accumulate deleterious mutations at a faster rate than large populations. The analysis of nonsynonymous (dN) versus synonymous (dS) substitution rates in birds versus mammals, however, has provided contradictory results, questioning the generality of the nearly neutral theory. Here we analyzed the impact of life history traits, taken as proxies of the effective population size, on molecular evolutionary and population genetic processes in amniotes, including the so far neglected reptiles. We report a strong effect of species body mass, longevity, and age of sexual maturity on genome-wide patterns of polymorphism and divergence across the major groups of amniotes, in agreement with the nearly neutral theory. Our results indicate that the rate of protein evolution in amniotes is determined in the first place by the efficiency of purifying selection against deleterious mutations-and this is true of both radical and conservative amino acid changes. Interestingly, the among-species distribution of dN/dS in birds did not follow this general trend: dN/dS was not higher in large, long-lived than in small, short-lived species of birds. We show that this unexpected pattern is not due to a more narrow range of life history traits, a lack of correlation between traits and Ne, or a peculiar distribution of fitness effects of mutations in birds. Our analysis therefore highlights the bird dN/dS ratio as a molecular evolutionary paradox and a challenge for future research.

  • 24.
    Frank, Carolin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Molecular Evolution.
    Alsmark, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Molecular Evolution.
    Thollesson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Molecular Evolution.
    Andersson, Siv
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Molecular Evolution.
    Functional divergence and horizontal transfer of type IV secretion systems2005In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 22, no 5, p. 1325-36Article in journal (Refereed)
    Abstract [en]

    The type IV secretion system (TFSSs) is a multifunctional family of translocation pathways that mediate the transfer of DNA among bacteria and deliver DNA and proteins to eukaryotic cells during bacterial infections. Horizontal transmission has dominated the evolution of the TFSS, as demonstrated here by a lack of congruence between the tree topology inferred from components of the TFSS and the presumed bacterial species divergence pattern. A parsimony analysis suggests that conjugation represents the ancestral state and that the divergence from conjugation to secretion of effector molecules has occurred independently at multiple sites in the tree. The result shows that the nodes at which functional shifts have occurred coincide with those of horizontal gene transfers among distantly related bacteria. We suggest that it is the transfer between species that paved the way for the divergence of the TFSSs and discuss the general role of horizontal gene transfers for the evolution of novel gene functions.

  • 25.
    Galtier, Nicolas
    et al.
    Univ Montpellier, Inst Sci Evolut, EPHE, CNRS,UMR5554,IRD, Montpellier, France.
    Roux, Camille
    Univ Montpellier, Inst Sci Evolut, EPHE, CNRS,UMR5554,IRD, Montpellier, France; Univ Lausanne, Dept Ecol & Evolut, Lausanne, Switzerland; Univ Lille Sci & Technol, CNRS, UMR Evo Eco Paleo 8198, Villeneuve Dascq, France.
    Rousselle, Marjolaine
    Univ Montpellier, Inst Sci Evolut, EPHE, CNRS,UMR5554,IRD, Montpellier, France.
    Romiguier, Jonathan
    Univ Montpellier, Inst Sci Evolut, EPHE, CNRS,UMR5554,IRD, Montpellier, France; Univ Lausanne, Dept Ecol & Evolut, Lausanne, Switzerland.
    Figuet, Emeric
    Univ Montpellier, Inst Sci Evolut, EPHE, CNRS,UMR5554,IRD, Montpellier, France.
    Glémin, Sylvain
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution. Univ Montpellier, Inst Sci Evolut, EPHE, CNRS,UMR5554,IRD, Montpellier, France.
    Bierne, Nicolas
    Univ Montpellier, Inst Sci Evolut, EPHE, CNRS,UMR5554,IRD, Montpellier, France.
    Duret, Laurent
    Univ Lyon 1, Univ Lyon, CNRS, Lab Biometrie & Biol Evolut,UMR 5558, Villeurbanne, France.
    Codon Usage Bias in Animals: Disentangling the Effects of Natural Selection, Effective Population Size, and GC-Biased Gene Conversion2018In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 35, no 5, p. 1092-1103Article in journal (Refereed)
    Abstract [en]

    Selection on codon usage bias is well documented in a number of microorganisms. Whether codon usage is also generally shaped by natural selection in large organisms, despite their relatively small effective population size (Ne), is unclear. In animals, the population genetics of codon usage bias has only been studied in a handful of model organisms so far, and can be affected by confounding, nonadaptive processes such as GC-biased gene conversion and experimental artefacts. Using population transcriptomics data, we analyzed the relationship between codon usage, gene expression, allele frequency distribution, and recombination rate in 30 nonmodel species of animals, each from a different family, covering a wide range of effective population sizes. We disentangled the effects of translational selection and GC-biased gene conversion on codon usage by separately analyzing GC-conservative and GC-changing mutations. We report evidence for effective translational selection on codon usage in large-Ne species of animals, but not in small-Ne ones, in agreement with the nearly neutral theory of molecular evolution. C- and T-ending codons tend to be preferred over synonymous G- and A-ending ones, for reasons that remain to be determined. In contrast, we uncovered a conspicuous effect of GC-biased gene conversion, which is widespread in animals and the main force determining the fate of AT↔GC mutations. Intriguingly, the strength of its effect was uncorrelated with Ne.

  • 26.
    Gioti, Anastasia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Mushegian, Alexandra A.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Strandberg, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics.
    Stajich, Jason E.
    Johannesson, Hanna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Unidirectional evolutionary transitions in fungal mating systems and the role of transposable elements2012In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 29, no 10, p. 3215-3226Article in journal (Refereed)
    Abstract [en]

    In the fungal kingdom, the evolution of mating systems is highly dynamic, varying even among closely related species. Rearrangements in the mating-type (mat) locus, which contains the major regulators of sexual development, are expected to underlie the transitions between self-sterility (heterothallism) and self-fertility (homothallism). However, both the genetic mechanisms and the direction of evolutionary transitions in fungal mating systems are under debate. Here, we present new sequences of the mat locus of four homothallic and one heterothallic species of the model genus Neurospora (Ascomycota). By examining the patterns of synteny among these sequences and previously published data, we show that the locus is conserved among heterothallic species belonging to distinct phylogenetic clades, while different gene arrangements characterize the four homothallic species. These results allowed us to ascertain a heterothallic ancestor for the genus, confirming the prediction of the dead-end theory on unidirectional transitions toward selfing. We show that at least four shifts from heterothallism to homothallism have occurred in Neurospora, three of which involve the acquisition of sequences of both mating types into the same haploid genome. We present evidence for two genetic mechanisms allowing these shifts: translocation and unequal crossover. Finally, we identified two novel retrotransposons and suggest that these have played a major role in mating-system transitions, by facilitating multiple rearrangements of the mat locus.

  • 27.
    Griffin, Robert M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Dean, Rebecca
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Grace, Jaime L.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Ryden, Patrik
    Friberg, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    The Shared Genome Is a Pervasive Constraint on the Evolution of Sex-Biased Gene Expression2013In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 30, no 9, p. 2168-2176Article in journal (Refereed)
    Abstract [en]

    Males and females share most of their genomes, and differences between the sexes can therefore not evolve through sequence divergence in protein coding genes. Sexual dimorphism is instead restricted to occur through sex-specific expression and splicing of gene products. Evolution of sexual dimorphism through these mechanisms should, however, also be constrained when the sexes share the genetic architecture for regulation of gene expression. Despite these obstacles, sexual dimorphism is prevalent in the animal kingdom and commonly evolves rapidly. Here, we ask whether the genetic architecture of gene expression is plastic and easily molded by sex-specific selection, or if sexual dimorphism evolves rapidly despite pervasive genetic constraint. To address this question, we explore the relationship between the intersexual genetic correlation for gene expression (r(MF)), which captures how independently genes are regulated in the sexes, and the evolution of sex-biased gene expression. Using transcriptome data from Drosophila melanogaster, we find that most genes have a high r(MF) and that genes currently exposed to sexually antagonistic selection have a higher average r(MF) than other genes. We further show that genes with a high r(MF) have less pronounced sex-biased gene expression than genes with a low r(MF) within D. melanogaster and that the strength of the r(MF) in D. melanogaster predicts the degree to which the sex bias of a gene's expression has changed between D. melanogaster and six other species in the Drosophila genus. In sum, our results show that a shared genome constrains both short- and long-term evolution of sexual dimorphism.

  • 28. Günther, Torsten
    et al.
    Lampei, Christian
    Schmid, Karl J
    Mutational bias and gene conversion affect the intraspecific nitrogen stoichiometry of the Arabidopsis thaliana transcriptome.2013In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 30, no 3, p. 561-8Article in journal (Refereed)
    Abstract [en]

    The transcriptome and proteome of Arabidopsis thaliana are reduced in nitrogen content when compared with other taxa, which may result from ecological nitrogen limitation. We hypothesized that if the A. thaliana transcriptome is selected for a low nitrogen content, nitrogen-reducing derived alleles of single nucleotide polymorphisms (SNPs) should segregate at higher frequencies than nitrogen-increasing alleles. This pattern should be stronger in populations with a larger effective population size (N(e)) if natural selection is more efficient in large than in small populations. We analyzed variation in the nitrogen content in the transcriptome of 80 natural accessions of A. thaliana. In contrast to our expectations, derived alleles increase the nitrogen content in all accessions, and there is a positive correlation between nitrogen difference and derived allele frequency, which is strongest with nonsynonymous SNPs (nsSNPs). Also, there is a positive correlation between nitrogen difference and N(e) that was mainly caused by nsSNPs. These observations led us to reject the hypothesis that the transcriptome of A. thaliana is currently under selection to reduce nitrogen content. Instead, we show that a change in nitrogen content is a side effect of interacting evolutionary factors that influence base composition and include mutational bias, purifying selection of functionally deleterious alleles, and GC-biased gene conversion. We provide strong evidence that GC-biased gene conversion may play an important role for base composition in the highly selfing plant A. thaliana.

  • 29.
    Haitina, Tatjana
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Pharmacology.
    Ringholm, Aneta
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Pharmacology.
    Kelly, Joanne
    Mundy, Nicholas I
    Schiöth, Helgi B.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Pharmacology.
    High diversity in functional properties of melanocortin 1 receptor (MC1R) in divergent primate species is more strongly associated with phylogeny than coat color2007In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 24, no 9, p. 2001-2008Article in journal (Refereed)
    Abstract [en]

    We have characterized the biochemical function of the melanocortin1 receptor (MC1R), a critical regulator of melanin synthesis,from 9 phylogenetically diverse primate species with varyingcoat colors. There is substantial diversity in melanocyte-stimulatinghormone (MSH) binding affinity and basal levels of activityin the cloned MC1Rs. MSH binding was lost independently in lemurand New World monkey lineages, whereas high basal levels ofMC1R activity occur in lemurs and some New World monkeys andOld World monkeys. Highest levels of basal activity were foundin the MC1R of ruffed lemurs, which have the E94K mutation thatleads to constitutive activation in other species. In 3 species(2 lemurs and the howler monkey), we report the novel findingthat binding and inhibition of MC1R by agouti signaling protein(ASIP) can occur when MSH binding has been lost, thus enablingcontinuing regulation of the melanin type via ASIP expression.Together, these findings can explain the previous paradox ofa predominantly pheomelanic coat in the red ruffed lemur (Vareciarubra). The presence of a functional, MSH-responsive MC1R inorangutan demonstrates that the mechanism of red hair generationin this ape is different from the prevalent mechanism in Europeanhuman populations. Overall, we have found unexpected diversityin MC1R function among primates and show that the evolutionof the regulatory control of MC1R activity occurs by independentvariation of 3 distinct mechanisms: basal MC1R activity, MSHbinding and activation, and ASIP binding and inhibition. Thisdiversity of function is broadly associated with primate phylogenyand does not have a simple relation to coat color phenotypewithin primate clades.

  • 30.
    He, Ding
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Systematic Biology.
    Fu, Cheng-Jie
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Systematic Biology.
    Baldauf, Sandra
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Systematic Biology.
    Multiple Origins of Eukaryotic cox15 Suggest Horizontal Gene Transfer from Bacteria to Jakobid Mitochondrial DNA2016In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 33, no 1, p. 122-133Article in journal (Refereed)
    Abstract [en]

    The most gene-rich and bacterial-like mitochondrial genomes known are those of Jakobida (Excavata). Of these, the most extreme example to date is the Andalucia godoyi mitochondrial DNA (mtDNA), including a cox15gene encoding the respiratory enzyme heme A synthase (HAS), which is nuclear-encoded in nearly all other mitochondriate eukaryotes. Thuscox15 in eukaryotes appears to be a classic example of mitochondrion-to-nucleus (endosymbiotic) gene transfer, with A. godoyi uniquely retaining the ancestral state. However, our analyses reveal two highly distinct HAS types (encoded by cox15-1 and cox15-2 genes) and identifyA. godoyi mitochondrial cox15-encoded HAS as type-1 and all other eukaryotic cox15-encoded HAS as type-2. Molecular phylogeny places the two HAS types in widely separated clades with eukaryotic type-2 HAS clustering with the bulk of α-proteobacteria (>670 sequences), whereas A. godoyi type-1 HAS clusters with an eclectic set of bacteria and archaea including two α-proteobacteria missing from the type-2 clade. This wide phylogenetic separation of the two HAS types is reinforced by unique features of their predicted protein structures. Meanwhile, RNA-sequencing and genomic analyses fail to detect either cox15 type in the nuclear genome of any jakobid including A. godoyi. This suggests that not only iscox15-1 a relatively recent acquisition unique to the Andalucia lineage but also the jakobid last common ancestor probably lacked both cox15 types. These results indicate that uptake of foreign genes by mtDNA is more taxonomically widespread than previously thought. They also caution against the assumption that all α-proteobacterial-like features of eukaryotes are ancient remnants of endosymbiosis.

  • 31.
    Hehenberger, Elisabeth
    et al.
    Univ British Columbia, Dept Bot, Canadian Inst Adv Res, Vancouver, BC, Canada..
    Burki, Fabien
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Systematic Biology. Univ British Columbia, Dept Bot, Canadian Inst Adv Res, Vancouver, BC, Canada..
    Kolisko, Martin
    Univ British Columbia, Dept Bot, Canadian Inst Adv Res, Vancouver, BC, Canada..
    Keeling, Patrick J.
    Univ British Columbia, Dept Bot, Canadian Inst Adv Res, Vancouver, BC, Canada..
    Functional Relationship between a Dinoflagellate Host and Its Diatom Endosymbiont2016In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 33, no 9, p. 2376-2390Article in journal (Refereed)
    Abstract [en]

    While we know much about the evolutionary patterns of endosymbiotic organelle origins, we know less about how the actual process unfolded within each system. This is partly due to the massive changes endosymbiosis appears to trigger, and partly because most organelles evolved in the distant past. The dinotoms are dinoflagellates with diatom endosymbionts, and they represent a relatively recent but nevertheless obligate endosymbiotic association. We have carried out deep sequencing of both the host and endosymbiont transcriptomes from two dinotoms, Durinskia baltica and Glenodinium foliaceum, to examine how the nucleocytosolic compartments have functionally integrated. This analysis showed little or no functional reduction in either the endosymbiont or host, and no evidence for genetic integration. Rather, host and endosymbiont seem to be bound to each other via metabolites, such as photosynthate exported from the endosymbiont to the host as indicated by the presence of plastidic phosphate translocators in the host transcriptome. The host is able to synthesize starch, using plant-specific starch synthases, as a way to store imported photosynthate.

  • 32. Hong, Xin
    et al.
    Scofield, Douglas
    Lynch, Michael
    Intron size, abundance, and distribution within untranslated regions of genes2006In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 23, no 12, p. 2392-2404Article in journal (Refereed)
    Abstract [en]

    Most research concerning the evolution of introns has largely considered introns within coding sequences (CDSs), without regard for introns located within untranslated regions (UTRs) of genes. Here, we directly determined intron size, abundance, and distribution in UTRs of genes using full-length cDNA libraries and complete genome sequences for four species,Arabidopsis thaliana, Drosophila melanogaster, human, and mouse. Overall intron occupancy (introns/exon kbp) is lower in 5′ UTRs than CDSs, but intron density (intron occupancy in regions containing introns) tends to be higher in 5′ UTRs than in CDSs. Introns in 5′ UTRs are roughly twice as large as introns in CDSs, and there is a sharp drop in intron size at the 5′ UTR-CDS boundary. We propose a mechanistic explanation for the existence of selection for larger intron size in 5′ UTRs, and outline several implications of this hypothesis. We found introns to be randomly distributed within 5′ UTRs, so long as a minimum required exon size was assumed. Introns in 3′ UTRs were much less abundant than in 5′ UTRs. Though this was expected for human and mouse that have intron-dependent nonsense-mediated decay (NMD) pathways that discourage the presence of introns within the 3′ UTR, it was also true for A. thaliana and D. melanogaster, which may lack intron-dependent NMD. Our findings have several implications for theories of intron evolution and genome evolution in general.

  • 33. Huber, Katharina T.
    et al.
    Oxelman, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Systematic Botany.
    Lott, Martin
    Moulton, Vincent
    Reconstructing the evolutionary history of polyploids from multilabeled trees2006In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 23, no 9, p. 1784-1791Article in journal (Refereed)
    Abstract [en]

    In recent studies, phylogenetic networks have been derived from so-called multilabeled trees in order to understand the origins of certain polyploids. Although the trees used in these studies were constructed using sophisticated techniques in phylogenetic analysis, the presented networks were inferred using ad hoc arguments that cannot be easily extended to larger, more complicated examples. In this paper, we present a general method for constructing such networks, which takes as input a multilabeled phylogenetic tree and outputs a phylogenetic network with certain desirable properties. To illustrate the applicability of our method, we discuss its use in reconstructing the evolutionary history of plant allopolyploids. We conclude with a discussion concerning possible future directions. The network construction method has been implemented and is freely available for use from http://www.uea.ac.uk/similar to a043878/padre.html.

  • 34.
    Huseby, Douglas L.
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Pietsch, Franziska
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Brandis, Gerrit
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Garoff, Linnéa
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Tegehall, Angelica
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Hughes, Diarmaid
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Mutation supply and relative fitness shape the genotypes of ciprofloxacin-resistant Escherichia coli2017In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 34, no 5, p. 1029-1039Article in journal (Refereed)
    Abstract [en]

    Ciprofloxacin is an important antibacterial drug targeting Type II topoisomerases, highly active against Gram-negatives including Escherichia coli. The evolution of resistance to ciprofloxacin in E. coli always requires multiple genetic changes, usually including mutations affecting two different drug target genes, gyrA and parC. Resistant mutants selected in vitro or in vivo can have many different mutations in target genes and efflux regulator genes that contribute to resistance. Among resistant clinical isolates the genotype, gyrA S83L D87N, parC S80I is significantly overrepresented suggesting that it has a selective advantage. However, the evolutionary or functional significance of this high frequency resistance genotype is not fully understood. By combining experimental data and mathematical modeling, we addressed the reasons for the predominance of this specific genotype. The experimental data were used to model trajectories of mutational resistance evolution under different conditions of drug exposure and population bottlenecks. We identified the order in which specific mutations are selected in the clinical genotype, showed that the high frequency genotype could be selected over a range of drug selective pressures, and was strongly influenced by the relative fitness of alternative mutations and factors affecting mutation supply. Our data map for the first time the fitness landscape that constrains the evolutionary trajectories taken during the development of clinical resistance to ciprofloxacin and explain the predominance of the most frequently selected genotype. This study provides strong support for the use of in vitro competition assays as a tool to trace evolutionary trajectories, not only in the antibiotic resistance field.

  • 35.
    Höglund, Pär J.
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Functional Pharmacology.
    Nordström, Karl J. V.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Functional Pharmacology.
    Schiöth, Helgi B.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Functional Pharmacology.
    Fredriksson, Robert
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Functional Pharmacology.
    The solute carrier families have a remarkably long evolutionary history with the majority of the human families present before divergence of Bilaterian species2011In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 28, no 4, p. 1531-1541Article in journal (Refereed)
    Abstract [en]

    The Solute Carriers (SLCs) are membrane proteins that regulate transport of many types of substances over the cell membrane. The SLCs are found in at least 46 gene families in the human genome. Here we performed the first evolutionary analysis of the entire SLC family based on whole genome sequences. We systematically mined and analyzed the genomes of seventeen species to identify SLC genes. In all we identified 4813 SLC sequences in these genomes and we delineated the evolutionary history of each of the subgroups. Moreover, we also identified 10 new human sequences not previously classified as SLCs, which most likely belong to the SLC family. We found that 43 of the 46 SLC families found in H. sapiens were also found in C. elegans, while 42 of them were also found in insects. Mammals have higher number of SLC genes in most families, perhaps reflecting important roles for these in central nervous system functions. This study provides systematic analysis of the evolutionary history of the SLC families in Eukaryotes showing that the SLC superfamily is ancient with multiple branches that were present before early divergence of Bilateria. The results provide foundation for overall classification of SLC genes and are valuable for annotation and prediction of substrates for the many SLCs that have not been tested in experimental transport assays.

  • 36.
    Innocenti, Paolo
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
    Chenoweth, Stephen F.
    Interspecific Divergence of Transcription Networks along Lines of Genetic Variance in Drosophila: Dimensionality, Evolvability, and Constraint2013In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 30, no 6, p. 1358-1367Article in journal (Refereed)
    Abstract [en]

    Change in gene expression is a major facilitator of phenotypic evolution. Understanding the evolutionary potential of gene expression requires taking into account complex systems of regulatory networks, the structure of which could potentially bias evolutionary trajectories. We analyzed the evolutionary potential and divergence of multigene expression in three well-characterized signaling pathways in Drosophila, the mitogen-activated protein kinase (MapK), the Toll, and the insulin receptor/Foxo (InR/Foxo or InR/TOR) pathways in a multivariate quantitative genetic framework. Gene expression data from a natural population of D. melanogaster were used to estimate the genetic variance-covariance matrices (G) for each network. Although most genes within each pathway exhibited significant genetic variance, the number of independent dimensions of multivariate genetic variance was fewer than the number of genes analyzed. However, for expression, the reduction in dimensionality was not as large as seen for other trait types such as morphology. We then tested whether gene expression divergence between D. melanogaster and an additional six species of the Drosophila genus was biased along the major axes of standing variation observed in D. melanogaster. In many cases, divergence was restricted to directions of phenotypic space harboring above average levels of genetic variance in D. melanogaster, indicating that genetic covariances between genes within pathways have biased interspecific divergence. We tested whether co-expression of genes in both sexes has also biased the pattern of divergence. Including cross-sex genetic covariances increased the degree to which divergence was biased along major axes of genetic variance, suggesting that the co-expression of genes in males and females can generate further constraints on divergence across the Drosophila phylogeny. In contrast to patterns seen for morphological traits in vertebrates, transcriptional constraints do not appear to break down as divergence time between species increases, instead they persist over tens of millions of years of divergence.

  • 37. Jay, Flora
    et al.
    Sjödin, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Jakobsson, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Blum, Michael G. B.
    Anisotropic Isolation by Distance: The Main Orientations of Human Genetic Differentiation2013In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 30, no 3, p. 513-525Article in journal (Refereed)
    Abstract [en]

    Genetic differentiation among human populations is greatly influenced by geography due to the accumulation of local allele frequency differences. However, little is known about the possibly different increment of genetic differentiation along the different geographical axes (north-south, east-west, etc.). Here, we provide new methods to examine the asymmetrical patterns of genetic differentiation. We analyzed genome-wide polymorphism data from populations in Africa (n = 29), Asia (n = 26), America (n = 9), and Europe (n = 38), and we found that the major orientations of genetic differentiation are north-south in Europe and Africa, and east-west in Asia, but no preferential orientation was found in the Americas. Additionally, we showed that the localization of the individual geographic origins based on single nucleotide polymorphism data was not equally precise along all orientations. Confirming our findings, we obtained that, in each continent, the orientation along which the precision is maximal corresponds to the orientation of maximum differentiation. Our results have implications for interpreting human genetic variation in terms of isolation by distance and spatial range expansion processes. In Europe, for instance, the precise northnorthwest-southsoutheast axis of main European differentiation cannot be explained by a simple Neolithic demic diffusion model without admixture with the local populations because in that case the orientation of greatest differentiation should be perpendicular to the direction of expansion. In addition to humans, anisotropic analyses can guide the description of genetic differentiation for other organisms and provide information on expansions of invasive species or the processes of plant dispersal.

  • 38. Jones, Christopher M.
    et al.
    Stres, Blaz
    Rosenquist, Magnus
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology, Clinical Immunology.
    Hallin, Sara
    Phylogenetic analysis of nitrite, nitric oxide, and nitrous oxide respiratory enzymes reveal a complex evolutionary history for denitrification2008In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 25, no 9, p. 1955-1966Article in journal (Refereed)
    Abstract [en]

    Denitrification is a facultative respiratory pathway in which nitrite (NO2(-)), nitric oxide (NO), and nitrous oxide (N2O) are successively reduced to nitrogen gas (N(2)), effectively closing the nitrogen cycle. The ability to denitrify is widely dispersed among prokaryotes, and this polyphyletic distribution has raised the possibility of horizontal gene transfer (HGT) having a substantial role in the evolution of denitrification. Comparisons of 16S rRNA and denitrification gene phylogenies in recent studies support this possibility; however, these results remain speculative as they are based on visual comparisons of phylogenies from partial sequences. We reanalyzed publicly available nirS, nirK, norB, and nosZ partial sequences using Bayesian and maximum likelihood phylogenetic inference. Concomitant analysis of denitrification genes with 16S rRNA sequences from the same organisms showed substantial differences between the trees, which were supported by examining the posterior probability of monophyletic constraints at different taxonomic levels. Although these differences suggest HGT of denitrification genes, the presence of structural variants for nirK, norB, and nosZ makes it difficult to determine HGT from other evolutionary events. Additional analysis using phylogenetic networks and likelihood ratio tests of phylogenies based on full-length sequences retrieved from genomes also revealed significant differences in tree topologies among denitrification and 16S rRNA gene phylogenies, with the exception of the nosZ gene phylogeny within the data set of the nirK-harboring genomes. However, inspection of codon usage and G + C content plots from complete genomes gave no evidence for recent HGT. Instead, the close proximity of denitrification gene copies in the genomes of several denitrifying bacteria suggests duplication. Although HGT cannot be ruled out as a factor in the evolution of denitrification genes, our analysis suggests that other phenomena, such gene duplication/divergence and lineage sorting, may have differently influenced the evolution of each denitrification gene.

  • 39.
    Kaiser, Vera B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    van Tuinen, Marcel
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Insertion Events of CR1 Retrotransposable Elements Elucidate the Phylogenetic Branching Order in Galliform Birds2007In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 24, no 1, p. 338-347Article in journal (Refereed)
    Abstract [en]

    Using standard phylogenetic methods, it can be hard to resolve the order in which speciation events took place when new lineages evolved in the distant past and within a short time frame. As an example, phylogenies of galliform birds (including well-known species such as chicken, turkey, and quail) usually show low bootstrap support values at short internal branches, reflecting the rapid diversification of these birds in the Eocene. However, given the key role of chicken and related poultry species in agricultural, evolutionary, general biological and disease studies, it is important to know their internal relationships. Recently, insertion patterns of transposable elements such as long and short interspersed nuclear element markers have proved powerful in revealing branching orders of difficult phylogenies. Here we decipher the order of speciation events in a group of 27 galliform species based on insertion events of chicken repeat 1 (CR1) transposable elements. Forty-four CR1 marker loci were identified from the draft sequence of the chicken genome, and from turkey BAC clone sequence, and the presence or absence of markers across species was investigated via electrophoretic size separation of amplification products and subsequent confirmation by DNA sequencing. Thirty markers proved possible to type with electrophoresis of which 20 were phylogenetically informative. The distribution of these repeat elements supported a single homoplasy-free cladogram, which confirmed that megapodes, cracids, New World quail, and guinea fowl form outgroups to Phasianidae and that quails, pheasants, and partridges are each polyphyletic groups. Importantly, we show that chicken is an outgroup to turkey and quail, an observation which does not have significant support from previous DNA sequence- and DNA-DNA hybridization-based trees and has important implications for evolutionary studies based on sequence or karyotype data from galliforms. We discuss the potential and limitations of using a genome-based retrotransposon approach in resolving problematic phylogenies among birds.

  • 40. Kapralov, Maxim V
    et al.
    Kubien, David S
    Andersson, Inger
    Department of Molecular Biology, Swedish University of Agricultural Sciences.
    Filatov, Dmitry A
    Changes in Rubisco kinetics during the evolution of C4 photosynthesis in Flaveria (Asteraceae) are associated with positive selection on genes encoding the enzyme.2011In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 28, no 4, p. 1491-1503Article in journal (Refereed)
    Abstract [en]

    Rubisco, the primary photosynthetic carboxylase, evolved 3-4 billion years ago in an anaerobic, high CO(2) atmosphere. The combined effect of low CO(2) and high O(2) levels in the modern atmosphere, and the inability of Rubisco to distinguish completely between CO(2) and O(2), leads to the occurrence of an oxygenation reaction that reduces the efficiency of photosynthesis. Among land plants, C(4) photosynthesis largely solves this problem by facilitating a high CO(2)/O(2) ratio at the site of Rubisco that resembles the atmosphere in which the ancestral enzyme evolved. The prediction that such conditions favor Rubiscos with higher kcat(CO2) and lower CO(2)/O(2) specificity (S(C/O)) is well supported, but the structural basis for the differences between C(3) and C(4) Rubiscos is not clear. Flaveria (Asteraceae) includes C(3), C(3)-C(4) intermediate, and C(4) species with kinetically distinct Rubiscos, providing a powerful system in which to study the biochemical transition of Rubisco during the evolution from C(3) to C(4) photosynthesis. We analyzed the molecular evolution of chloroplast rbcL and nuclear rbcS genes encoding the large subunit (LSu) and small subunit (SSu) of Rubisco from 15 Flaveria species. We demonstrate positive selection on both subunits, although selection is much stronger on the LSu. In Flaveria, two positively selected LSu amino acid substitutions, M309I and D149A, distinguish C(4) Rubiscos from the ancestral C(3) species and statistically account for much of the kinetic difference between the two groups. However, although Flaveria lacks a characteristic "C(4)" SSu, our data suggest that specific residue substitutions in the SSu are correlated with the kinetic properties of Rubisco in this genus.

  • 41.
    Karlsson, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Evolutionary Biology.
    Nygren, Kristiina
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Evolutionary Biology.
    Johannesson, Hanna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Evolutionary Biology.
    The evolution of the pheromonal signal system and its potential role for reproductive isolation in heterothallic neurospora2008In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 25, no 1, p. 168-178Article in journal (Refereed)
    Abstract [en]

    Comparative sequencing studies among a wide range of taxonomic groups, including fungi, provide the overall pattern that reproductive genes evolve more rapidly than other genes, and this divergence is believed to be important in the establishment of reproductive barriers between species. In this study, we investigated the molecular evolution of the pheromone receptor genes pre-1 and pre-2 of strains belonging to 12 and 13 heterothallic taxa, respectively, of the model genus Neurospora. Furthermore, we examined the regulatory pattern of both pheromone precursor and receptor genes during sexual crosses of Neurospora crassa and Neurospora intermedia, for which reinforcement of interspecific reproductive barriers in sympatry previously has been documented. We conclude that the part encoding the C-terminal intracellular domain of pre-1 and pre-2 genes evolves rapidly. Both stochastic and directional processes drive this divergence; both genes contain neutrally evolving codons, and in addition, pre-1 contains codons evolving under positive selection, whereas in pre-2 we found highly variable regions with numerous repeats encoding glycine, threonine, or aspartic acid. In addition, we found regulatory changes of the pheromone and receptor genes during crosses between N. crassa and N. intermedia with different reproductive success. Gene expression levels are higher in the interspecific sympatric crosses with low reproductive success than in their intraspecific and/or allopatric equivalents, both at the stage of initial communication and contact and later at postfertilization stages. Taken together, our data indicate that pheromones and receptors are important key players during reproductive isolation between Neurospora species, and this study provides a general framework for future studies on the role of reproductive proteins for reproductive isolation.

  • 42.
    Klasson, Lisa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Molecular Evolution.
    Andersson, Siv
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Molecular Evolution.
    Strong asymmetric mutation bias in endosymbiont genomes coincide with loss of genes for replication restart pathways2006In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 23, no 5, p. 1031-1039Article in journal (Refereed)
    Abstract [en]

    A large majority of bacterial genomes show strand asymmetry, such that G and T preferentially accumulate on the leading strand. The mechanisms are unknown, but cytosine deaminations are thought to play an important role. Here, we have examined DNA strand asymmetry in three strains of the aphid endosymbiont Buchnera aphidicola. These are phylogenetically related, have similar genomic GC contents, and conserved gene order structures, yet B. aphidicola (Bp) shows a fourfold higher replication-induced strand bias than B. aphidicola (Sg) and (Ap). We rule out an increase in the overall substitution frequency as the major cause of the stronger strand bias in B. aphidicola (Bp). Instead, the results suggest that the higher GC skew in this species is caused by a different spectrum of mutations, including a relatively higher frequency of C to T mutations on the leading strand and/or of G to A mutations on the lagging strand. A comparative analysis of 20 γ-proteobacterial genomes revealed that endosymbiont genomes lacking recA and other genes involved in replication restart processes, such as priA, which codes for primosomal helicase PriA, displayed the strongest strand bias. We hypothesize that cytosine deaminations accumulate during single-strand exposure at arrested replication forks and that inefficient restart mechanisms may lead to high DNA strand asymmetry in bacterial genomes.

  • 43. Klasson, Lisa
    et al.
    Walker, Thomas
    Sebaihia, Mohammed
    Sanders, Mandy J
    Quail, Michael A
    Lord, Angela
    Sanders, Susanne
    Earl, Julie
    O'Neill, Scott L
    Thomson, Nicholas
    Sinkins, Steven P
    Parkhill, Julian
    Genome evolution of Wolbachia strain wPip from the Culex pipiens group.2008In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 25, no 9, p. 1877-87Article in journal (Refereed)
    Abstract [en]

    The obligate intracellular bacterium Wolbachia pipientis strain wPip induces cytoplasmic incompatibility (CI), patterns of crossing sterility, in the Culex pipiens group of mosquitoes. The complete sequence is presented of the 1.48-Mbp genome of wPip which encodes 1386 coding sequences (CDSs), representing the first genome sequence of a B-supergroup Wolbachia. Comparisons were made with the smaller genomes of Wolbachia strains wMel of Drosophila melanogaster, an A-supergroup Wolbachia that is also a CI inducer, and wBm, a mutualist of Brugia malayi nematodes that belongs to the D-supergroup of Wolbachia. Despite extensive gene order rearrangement, a core set of Wolbachia genes shared between the 3 genomes can be identified and contrasts with a flexible gene pool where rapid evolution has taken place. There are much more extensive prophage and ankyrin repeat encoding (ANK) gene components of the wPip genome compared with wMel and wBm, and both are likely to be of considerable importance in wPip biology. Five WO-B-like prophage regions are present and contain some genes that are identical or highly similar in multiple prophage copies, whereas other genes are unique, and it is likely that extensive recombination, duplication, and insertion have occurred between copies. A much larger number of genes encode ankyrin repeat (ANK) proteins in wPip, with 60 present compared with 23 in wMel, many of which are within or close to the prophage regions. It is likely that this pattern is partly a result of expansions in the wPip lineage, due for example to gene duplication, but their presence is in some cases more ancient. The wPip genome underlines the considerable evolutionary flexibility of Wolbachia, providing clear evidence for the rapid evolution of ANK-encoding genes and of prophage regions. This host-Wolbachia system, with its complex patterns of sterility induced between populations, now provides an excellent model for unraveling the molecular systems underlying host reproductive manipulation.

  • 44.
    Klinger, Christen M.
    et al.
    Univ Alberta, Dept Cell Biol, Edmonton, AB, Canada..
    Spang, Anja
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Dacks, Joel B.
    Univ Alberta, Dept Cell Biol, Edmonton, AB, Canada..
    Ettema, Thijs J. G.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Tracing the Archaeal Origins of Eukaryotic Membrane-Trafficking System Building Blocks2016In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 33, no 6, p. 1528-1541Article in journal (Refereed)
    Abstract [en]

    In contrast to prokaryotes, eukaryotic cells are characterized by a complex set of internal membrane-bound compartments. A subset of these, and the protein machineries that move material between them, define the membrane-trafficking system (MTS), the emergence of which represents a landmark in eukaryotic evolution. Unlike mitochondria and plastids, MTS organelles have autogenous origins. Much of the MTS machinery is composed of building blocks, including small GTPase, coiled-coil, beta-propeller + alpha-solenoid, and longin domains. Despite the identification of prokaryotic proteins containing these domains, only few represent direct orthologues, leaving the origins and early evolution of the MTS poorly understood. Here, we present an in-depth analysis of MTS building block homologues in the composite genome of Lokiarchaeum, the recently discovered archaeal sister clade of eukaryotes, yielding several key insights. We identify two previously unreported Eukaryotic Signature Proteins; orthologues of the Gtr/Rag family GTPases, involved in target of rapamycin complex signaling, and of the RLC7 dynein component. We could not identify golgin or SNARE (coiled-coil) or beta-propeller + alpha-solenoid orthologues, nor typical MTS domain fusions, suggesting that these either were lost from Lokiarchaeum or emerged later in eukaryotic evolution. Furthermore, our phylogenetic analyses of lokiarchaeal GTPases support a split into Ras-like and Arf-like superfamilies, with different prokaryotic antecedents, before the advent of eukaryotes. While no GTPase activating proteins or exchange factors were identified, we show that Lokiarchaeum encodes numerous roadblock domain proteins and putative longin domain proteins, confirming the latter's origin from Archaea. Altogether, our study provides new insights into the emergence and early evolution of the eukaryotic membrane-trafficking system.

  • 45.
    Klovins, Janis
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience. Farmakologi 3.
    Haitina, Tatjana
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience. Farmakologi 3.
    Fridmanis, Davids
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience. Farmakologi 3.
    Kilianova, Z
    Kapa, Ivo
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience. Farmakologi 3.
    Fredriksson, Robert
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience. Farmakologi 3.
    Gallo-Payet, N
    Schiöth, HB
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience. Farmakologi 3.
    The melanocortin system in Fugu: determination of POMC/AGRP/MCR gene repertoire and synteny, as well as pharmacology and anatomical distribution of the MCRs2004In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 21, no 3, p. 563-79Article in journal (Refereed)
    Abstract [en]

    The G-protein-coupled melanocortin receptors (MCRs) play an important role in a variety of essential functions such as the regulation of pigmentation, energy homeostasis, and steroid production. We performed a comprehensive characterization of the MC system in Fugu (Takifugu rubripes). We show that Fugu has an AGRP gene with high degree of conservation in the C-terminal region in addition to a POMC gene lacking gamma-MSH. The Fugu genome contains single copies of four MCRs, whereas the MC3R is missing. The MC2R and MC5R are found in tandem and remarkably contain one and two introns, respectively. We suggest that these introns were inserted through a reverse splicing mechanism into the DRY motif that is widely conserved through GPCRs. We were able to assemble large blocks around the MCRs in Fugu, showing remarkable synteny with human chromosomes 16 and 18. Detailed pharmacological characterization showed that ACTH had surprisingly high affinity for the Fugu MC1R and MC4R, whereas alpha-MSH had lower affinity. We also showed that the MC2R gene in Fugu codes for an ACTH receptor, which did not respond to alpha-MSH. All the Fugu receptors were able to couple functionally to cAMP production in line with the mammalian orthologs. The anatomical characterization shows that the MC2R is expressed in the brain in addition to the head-kidney, whereas the MC4R and MC5R are found in both brain regions and peripheral tissues. This is the first comprehensive genomic and functional characterization of a GPCR family within the Fugu genome. The study shows that some parts of the MC system are highly conserved through vertebrate evolution, such as regions in POMC coding for ACTH, alpha-MSH, and beta-MSH, the C-terminal region of AGRP, key binding units within the MC1R, MC2R, MC4R, and MC5R, synteny blocks around the MCRs, pharmacological properties of the MC2R, whereas other parts in the system are either missing, such as the MC3R and gamma-MSH, or different as compared to mammals, such as the affinity of ACTH and MSH peptides to MC1R and MC4R and the anatomical expression pattern of the MCRs.

  • 46.
    Knopp, Michael
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Andersson, Dan I.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Amelioration of the Fitness Costs of Antibiotic Resistance Due To Reduced Outer Membrane Permeability by Upregulation of Alternative Porins2015In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 32, no 12, p. 3252-3263Article in journal (Refereed)
    Abstract [en]

    The fitness cost of antibiotic resistance is a key parameter in determining the evolutionary success of resistant bacteria. Studies of the effect of antibiotic resistance on bacterial fitness are heavily biased toward target alterations. Here we investigated how the costs in the form of a severely impaired growth rate associated with resistance due to absence of two major outer membrane porins can be genetically compensated. We performed an evolution experiment with 16 lineages of a double mutant of Escherichia coli with the ompCF genes deleted, and reduced fitness and increased resistance to different classes of antibiotics, including the carbapenems ertapenem and meropenem. After serial passage for only 250 generations, the relative growth rate increased from 0.85 to 0.99 (susceptible wild type set to 1.0). Compensation of the costs followed two different adaptive pathways where upregulation of expression of alternative porins bypassed the need for functional OmpCF porins. The first compensatory mechanism involved mutations in the phoR and pstS genes, causing constitutive high-level expression of the PhoE porin. The second mechanism involved mutations in the hfq and chiX genes that disrupted Hfq-dependent small RNA regulation, causing overexpression of the ChiP porin. Although susceptibility was restored in compensated mutants with PhoE overexpression, evolved mutants with high ChiP expression maintained the resistance phenotype. Our findings may explain why porin composition is often altered in resistant clinical isolates and provide new insights into how bypass mechanisms may allow genetic adaptation to a common multidrug resistance mechanism.

  • 47.
    Knöppel, Anna
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Lind, Peter A.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Lustig, Ulrika
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Näsvall, Joakim
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Andersson, Dan I.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Minor Fitness Costs in an Experimental Model of Horizontal Gene Transfer in Bacteria2014In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 31, no 5, p. 1220-1227Article in journal (Refereed)
    Abstract [en]

    Genes introduced by horizontal gene transfer (HGT) from other species constitute a significant portion of many bacterial genomes, and the evolutionary dynamics of HGTs are important for understanding the spread of antibiotic resistance and the emergence of new pathogenic strains of bacteria. The fitness effects of the transferred genes largely determine the fixation rates and the amount of neutral diversity of newly acquired genes in bacterial populations. Comparative analysis of bacterial genomes provides insight into what genes are commonly transferred, but direct experimental tests of the fitness constraints on HGT are scarce. Here, we address this paucity of experimental studies by introducing 98 random DNA fragments varying in size from 0.45 to 5 kb from Bacteroides, Proteus, and human intestinal phage into a defined position in the Salmonella chromosome and measuring the effects on fitness. Using highly sensitive competition assays, we found that eight inserts were deleterious with selection coefficients (s) ranging from a parts per thousand -0.007 to -0.02 and 90 did not have significant fitness effects. When inducing transcription from a P-BAD promoter located at one end of the insert, 16 transfers were deleterious and 82 were not significantly different from the control. In conclusion, a major fraction of the inserts had minor effects on fitness implying that extra DNA transferred by HGT, even though it does not confer an immediate selective advantage, could be maintained at selection-transfer balance and serve as raw material for the evolution of novel beneficial functions.

  • 48.
    Knöppel, Anna
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Näsvall, Joakim
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Andersson, Dan I.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Compensating the fitness costs of synonymous mutations2016In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 33, no 6, p. 1461-1477Article in journal (Refereed)
    Abstract [en]

    Synonymous mutations do not change the sequence of the polypeptide but they may still influence fitness. We investigated in Salmonella enterica how four synonymous mutations in the rpsT gene (encoding ribosomal protein S20) reduce fitness (i.e. growth rate) and the mechanisms by which this cost can be genetically compensated. The reduced growth rates of the synonymous mutants were correlated with reduced levels of the rpsT transcript and S20 protein. In an adaptive evolution experiment these fitness impairments could be compensated by mutations that either caused up-regulation of S20 through increased gene dosage (due to duplications), increased transcription of the rpsT gene (due to an rpoD mutation or mutations in rpsT), or increased translation from the rpsT transcript (due to rpsT mutations). We suggest that the reduced levels of S20 in the synonymous mutants result in production of a defective subpopulation of 30S subunits lacking S20 that reduce protein synthesis and bacterial growth and that the compensatory mutations restore S20 levels and the number of functional ribosomes. Our results demonstrate how specific synonymous mutations can cause substantial fitness reductions and that many different types of intra- and extragenic compensatory mutations can efficiently restore fitness. Furthermore, our study highlights that also synonymous sites can be under strong selection, which may have implications for the use of dN/dS ratios as signature for selection.

  • 49.
    Künstner, Axel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Nabholz, Benoit
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Ellegren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
    Evolutionary Constraint in Flanking Regions of Avian Genes2011In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 28, no 9, p. 2481-2489Article in journal (Refereed)
    Abstract [en]

    An important comprehension from comparative genomic analysis is that sequence conservation beyond neutral expectations is frequently found outside protein-coding regions, indicating important functional roles of noncoding DNA. Understanding the causes of constraint on noncoding sequence evolution forms an important area of research, not least in light of the importance for understanding the evolution of gene expression. We aligned all orthologous genes of chicken and zebra finch together with 5 kb of their upstream and downstream noncoding sequences, to study the evolution of gene flanking sequences in the avian genome. Using ancestral repeats as a neutral reference, we detected significant evolutionary constraint in the 3' flanking region, highest directly after termination (60%) and then gradually decreasing to about 20% 5 kb downstream. Constraint was higher in annotated 3' untranslated regions (UTRs) than in non-UTRs at the same distance from the stop codon and higher in sequences annotated as microRNA (miRNA)-binding sites than in non-miRNA-binding sites within 3' UTRs. Constraint was also higher when estimated for a smaller data set of genes from more closely related songbird species, indicating turnover of functional elements during avian evolution. On the 5' flanking side constraint was readily seen within the first 125 bp immediately upstream of the start codon (34%) and was about 10% for remaining sequence within 5 kb upstream. Analysis of chicken polymorphism data gave further support for the highest constraint directly before and after the translated region. Finally, we found that genes evolving under the highest constraint measured by d(N)/d(S) also had the highest level of constraint in the 3' flanking region. This study broadens the insights into gene flanking sequence evolution by adding new findings from a vertebrate lineage other than mammals.

  • 50. Leino, Matti W.
    et al.
    Hagenblad, Jenny
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Ecological Botany.
    Nineteenth Century Seeds Reveal the Population Genetics of Landrace Barley (Hordeum vulgare)2010In: Molecular biology and evolution, ISSN 0737-4038, E-ISSN 1537-1719, Vol. 27, no 4, p. 964-973Article in journal (Refereed)
    Abstract [en]

    Barley (Hordeum vulgare) is a major crop, grown worldwide and in a wide range of climatic conditions. Despite its importance as a crop species, little is known about the population genetics of barley and the effects of bottlenecks, adaptation, and gene flow on genetic diversity within and between landrace populations. In areas with highly developed agriculture, such as Northern Europe, these types of genetic studies are hampered by lack of landraces preserved in situ or ex situ. Here, we report a genetic study of Swedish landrace barley using 113-year-old seed samples. The results demonstrate differing levels of variation with some latitudinal effect. We also detect clear population differentiation and population structure within Sweden into a southern and a northern cluster. These results possibly reflect different introduction routes of barley into Sweden. We thus show that the study of historic material can be an important alternative for regions where no or little extant landrace material is available.

123 1 - 50 of 112
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