uu.seUppsala University Publications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
A comprehensive phylogeny of Neurospora reveals a link between reproductive mode and molecular evolution in fungi
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Systematic Biology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
Show others and affiliations
2011 (English)In: Molecular Phylogenetics and Evolution, ISSN 1055-7903, E-ISSN 1095-9513, Vol. 59, no 3, 649-663 p.Article in journal (Refereed) Published
Abstract [en]

The filamentous ascomycete genus Neurospora encompasses taxa with a wide range of reproductive modes. Sexual reproduction in this genus can be divided into three major modes; heterothallism (self-incompatibility), homothallism (self-compatibility) and pseudohomothallism (partial self-compatibility). In addition to the sexual pathway, most of the heterothallic taxa propagate with morphologically distinct, vegetative dissemination propagules (macroconidia), while this feature is undetected in the majority of the homothallic taxa. In this study, we used sequence information of seven nuclear gene loci from 43 taxa (295 of the possible 301 locus-by-taxon combinations) to create a phylogeny of Neurospora. The results suggest that transitions in reproductive mode have occurred at multiple times within this group of fungi. Although a homothallic ancestor would imply fewer switches in reproductive mode, we argue that the ancestor of Neurospora was likely heterothallic and that homothallism has evolved independently at least six times in the evolutionary history of the genus. Furthermore, the two pseudohomothallic taxa of Neurospora (N. tetrasperma and N. tetraspora) represent two independent origins of pseudohomothallism. Likelihood ratio tests of substitution rates among branches in the phylogeny indicate that reproductive mode is an important factor driving genome evolution in Neurospora. First, an increased level of non-synonymous/synonymous substitutions in branches delineating homothallic taxa was found, suggesting a reduced efficiency of purifying selection in these taxa. Furthermore, elevated nucleotide substitution rates were found in heterothallic, conidia-producing, lineages as compared to the homothallic non-conidiating lineages. The latter finding is likely due to the presence of conidia, i.e., a higher rate of mitotic divisions inducing mutations, and/or that the homothallic taxa have evolved a lower mutation rate to avoid genomic degeneration.

Place, publisher, year, edition, pages
2011. Vol. 59, no 3, 649-663 p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:uu:diva-167868DOI: http://dx.doi.org/10.1016/j.ympev.2011.03.023OAI: oai:DiVA.org:uu-167868DiVA: diva2:488659
Available from: 2012-02-02 Created: 2012-02-02 Last updated: 2017-12-08Bibliographically approved
In thesis
1. On the Evolution of Reproductive Systems in Neurospora
Open this publication in new window or tab >>On the Evolution of Reproductive Systems in Neurospora
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this thesis was to study the evolution of reproductive systems and reproductive traits in the fungal genus Neurospora. More specifically, I have investigated the evolutionary forces shaping the genes involved in sexual reproduction, focusing on mating-type (mat) and pheromone receptor (pre) genes. Neurospora contains species exhibiting three different mating systems, i.e., heterothallism (self-incompatibility), homothallism (self-compatibility) and pseudohomothallism (partial self-incompatibility). First, a robust phylogeny of Neurospora was established. The phylogenetic analyses revealed multiple independent transitions in reproductive life style during the evolutionary history of the genus. We argued for a heterothallic ancestor of the genus, although our subsequent ancestral reconstruction analyses favored a homothallic ancestor. To be able to settle the ancestral mating system, we zoomed in on the structural architecture of the mat-locus in four homothallic species of Neurospora, thought to have arisen from independent transitions. Our results led us to suggest two different genetic mechanisms (translocation and unequal crossover) to explain the transitions in mating system from heterothallism to homothallism. We pointed out that the mating-system transitions in Neurospora are unidirectional, and suggested that transposable elements might be driving the transitions. In conclusion, we suggest a heterothallic ancestor for Neurospora, and that at least six transitions to homothallism and two transitions to pseudohomothallism have occurred in its evolutionary history. Further, we used the phylogeny of Neurospora as a framework to test if the evolution of pre-genes (pre-1 and pre-2) in hetero- and homothallic Neurospora is dependent on mating systems and/or even the homothallic clades themselves (i.e., mating-system and/or switch-dependent). The molecular evolution results suggest that pre-1 and pre-2 are overall functional in both homothallic and heterothallic Neurospora. The molecular evolution of pre-1 seems to be independent of mating-system or homothallic clade, and we detected signs for positive selection in the C-terminal tail. For pre-2 we found no support for mating-system dependent evolution, but indications for switch-dependent evolution. In this study we also included expression analyses of both pre- as well as mat-genes, with the prospect to assess functionality and regulation. During this thesis work, we also performed a phylogenetic study were we found that reproductive genes might be more permeable to introgression than other genes, which is in contrast to theoretical expectations. In the last study, we confirmed the co-existence of two alternative splice variants of the pheromone receptor gene pre-1 in Neurospora crassa, and performed expression profiles studies using quantitative RT-PCR. I hope this thesis work will further strengthen Neurospora as a model for research in evolutionary genetics.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 41 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 895
Keyword
Neurospora, mating type, pheromone receptor, phylogeny, gene expression, heterothallism, homothallism, pseudohomothallism, alternative splicing
National Category
Natural Sciences
Research subject
Biology with specialization in Evolutionary Genetics
Identifiers
urn:nbn:se:uu:diva-167875 (URN)978-91-554-8265-7 (ISBN)
Public defence
2012-03-16, Lindahlsalen, EBC, Norbyvägen 14, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2012-02-24 Created: 2012-02-02 Last updated: 2012-03-01Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text
By organisation
Evolutionary BiologySystematic Biology
In the same journal
Molecular Phylogenetics and Evolution
Natural Sciences

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 501 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf