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Large-scale suppression of recombination predates genomic rearrangements in Neurospora tetrasperma
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 Organismal Biology, Systematic Biology.
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2017 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723Article in journal (Refereed) In press
Abstract [en]

A common feature of eukaryote genomes is large chromosomal regions where recombination is absent or strongly reduced, but the factors that cause this reduction are not well understood. Genomic rearrangements have often been implicated, but they may also be a consequence of recombination suppression rather than a cause. In this study, we generate eight high-quality genomic datasets of N. tetrasperma, a fungus that lacks recombination over most of its largest chromosome. The genomes surprisingly reveal collinearity of the non-recombining regions and although large inversions are enriched in these regions, we conclude these inversions to be derived and not the cause of the suppression. To our knowledge, this is the first time that non-recombining, genic regions as large as 86% of a full chromosome (or 8 Mbp), are shown to be collinear. These findings are of significant interest for our understanding of the evolution of sex chromosomes and other supergene complexes.

Place, publisher, year, edition, pages
2017.
Keyword [en]
Genome evolution, recombination, suppression of recombination, inversions, Neurospora tetrasperma
National Category
Evolutionary Biology
Research subject
Biology with specialization in Evolutionary Genetics
Identifiers
URN: urn:nbn:se:uu:diva-329496OAI: oai:DiVA.org:uu-329496DiVA: diva2:1141857
Available from: 2017-09-17 Created: 2017-09-17 Last updated: 2017-11-29
In thesis
1. Catching the Spore killers: Genomic conflict and genome evolution in Neurospora
Open this publication in new window or tab >>Catching the Spore killers: Genomic conflict and genome evolution in Neurospora
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A genome is shaped by many different forces. Recombination can for instance both create and maintain genetic diversity, but the need to locally reduce recombination rates will also leave specific signatures. Genetic elements can act selfishly and spreading at the expense of the rest of the genome can leave marks of their activity, as can mechanisms that suppresses them, in a phenomenon known as genomic conflict. In this thesis, I have studied the forces driving genome evolution, using modern genome sequencing techniques and with a special focus on a class of selfish genetic elements known as Spore killers found in the fungus Neurospora. First, we show novel findings on large-scale suppression of recombination by non-structural means in the N. tetrasperma genomes. In contrary, in the genomic region harbouring the spore killer elements Sk-2 and Sk-3 of N. intermedia, a dense set of inversions that are interspersed with transposable elements have accumulated. The inversions are unique for each killer type, showing that they have a long separated evolutionary history and likely have established themselves independently. For the Sk-2 haplotype, where we have polymorphism data, we see signs of relaxed selection, which is consistent with the hypothesis that recombination suppression reduces the efficacy of selection in this region. These results show the strong effects the divergent selective forces of genomic conflicts can have on chromosome architecture. Furthermore, we investigate the hypothesis that spore killing can drive reproductive isolation, by comparing the fertility of crosses between N. metzenbergii and either killer or non-killer N. intermedia strains. We show that crosses with spore killer strains have lower fertility, which cannot be explained by the killing itself, but is potentially caused by an incompatibility gene captured in the non-recombining region. Finally, we identified the genetic element responsible for causing spore killing in the Sk-1 spore killer strains found in N. sitophila. Unlike the Sk-2 and Sk-3 elements, Sk-1 is not connected to a large, non-recombining region, but is caused by a single locus, and we also find indications that this locus was introgressed from N. hispaniola.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 51 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1561
Keyword
Genomics, genomic conflict, genome evolution, meiotic drive, spore killer, suppression of recombination, inversions, fungi, Neurospora
National Category
Evolutionary Biology
Research subject
Biology
Identifiers
urn:nbn:se:uu:diva-329498 (URN)978-91-513-0074-0 (ISBN)
Public defence
2017-11-03, Lindahlsalen, Norbyvägen 18A, Uppsala, 09:00
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Available from: 2017-10-13 Created: 2017-09-17 Last updated: 2017-10-18

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