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A global multilocus analysis of the model fungus Neurospora reveals a single recent origin of a novel genetic system
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
University of Ottawa.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Evolutionary Biology.
Universidad de Sevilla.
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2014 (English)In: Molecular Phylogenetics and Evolution, ISSN 1055-7903, E-ISSN 1095-9513, Vol. 78, 136-147 p.Article in journal (Refereed) Published
Abstract [en]

The large diversity of mating systems observed in the fungal kingdom underlines the importance of mating system change in fungal evolution. The selfing species Neurospora tetrasperma has evolved a novel method of achieving self-fertility by a mating system referred to as pseudohomothallism. However, little is known about the origin of N. tetrasperma and its relationship to the self-sterile, heterothallic, Neurospora species. In this study, we used a combination of phylogenetic and population genetic analyses to reconstruct the evolutionary history of N. tetrasperma and its heterothallic relatives. We sequenced 9 unlinked nuclear loci from 106 strains of N. tetrasperma sampled from across the globe, and a sample of 28 heterothallic strains of Neurospora. Our analyses provide strong support for monophyly of N. tetrasperma, but reject the monophyly of N. crassa. We estimate that N. tetrasperma is of a recent origin and that it diverged from the heterothallic species ~1 million years ago. We also extend previous findings on the diversification within the N. tetrasperma clade, with 10 lineages identified. Taken together, these findings indicate that N. tetrasperma is younger than has been previously reported and that a rapid diversification of lineages has occurred within the N. tetrasperma clade.

Place, publisher, year, edition, pages
2014. Vol. 78, 136-147 p.
Keyword [en]
Mating Systems, Population Structure, Phylogenetics, Neurospora
National Category
Evolutionary Biology
Research subject
Evolutionary Genetics
Identifiers
URN: urn:nbn:se:uu:diva-208792DOI: 10.1016/j.ympev.2014.05.007ISI: 000342480400012OAI: oai:DiVA.org:uu-208792DiVA: diva2:654569
Available from: 2013-10-07 Created: 2013-10-07 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Neurospora tetrasperma from Natural Populations: Toward the Population Genomics of a Model Fungus
Open this publication in new window or tab >>Neurospora tetrasperma from Natural Populations: Toward the Population Genomics of a Model Fungus
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The study of DNA sequence variation is a powerful approach to study genome evolution, and to reconstruct evolutionary histories of species. In this thesis, I have studied genetic variation in the fungus Neurospora tetrasperma and other closely related Neurospora species. I have focused on N. tetrasperma in my research because it has large regions of suppressed recombination on its mating-type chromosomes, had undergone a recent change in reproductive mode and is composed of multiple reproductively isolated lineages. Using DNA sequence data from a large sample set representing multiple species of Neurospora I estimated that N. tetrasperma evolved ~1 million years ago and that it is composed of at least 10 lineages. My analysis of the type of asexual spores produced using newly described N. tetrasperma populations in Britain revealed that lineages differ considerably in life history characteristics that may have consequences for their evolution. A comparative genomic analysis using three genomes of N. tetrasperma and the genome of N. crassa revealed that the mat a chromosomes in the lineages examine have been introgressed from other Neurospora species and that this introgression has reduced levels of molecular degeneration on the mating-type chromosomes. Finally, I generated a population genomic dataset composed of 92 N. tetrasperma genomes and two genomes of other Neurospora species. Analysis of these genomes revealed that all strains of N. tetrasperma have large regions of suppressed recombination on their mating-type chromosomes ranging from 69-84% of the chromosome and that the extent of divergence between mating-type chromosomes within lineages varies greatly (from 1.3 to 3.2%). I concluded that the source of this great divergence mating-type chromosome is large-scale introgression from other Neurospora species, and that these introgressed tracts have become fixed within N. tetrasperma lineages. I also discovered that genes within non-recombining introgressed regions of the mating-type chromosome have severely reduced levels of genetic variation as compared to the autosomes, and exhibit signatures of reduced molecular degeneration. My analysis of variation in coding regions revealed that positive selection on the introgressed regions has resulted in the removal of deleterious mutations and is responsible for the reductions in molecular degeneration observed.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. 52 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1084
Keyword
Neurospora, poulation genetics, genomes, introgression
National Category
Evolutionary Biology Genetics
Research subject
Evolutionary Genetics
Identifiers
urn:nbn:se:uu:diva-208791 (URN)978-91-554-8771-3 (ISBN)
Public defence
2013-11-22, Zootisalen, EBC, Uppsala, 09:00 (English)
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Supervisors
Available from: 2013-10-31 Created: 2013-10-07 Last updated: 2014-01-23

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Lascoux, MartinJohannesson, Hanna

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