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Mobile introns shape the genetic diversity of their host genes

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Title: Mobile introns shape the genetic diversity of their host genes
Authors: Repar, J
Warnecke, T
Item Type: Journal Article
Abstract: Self-splicing introns populate several highly conserved protein-coding genes in fungal and plant mitochondria. In fungi, many of these introns have retained their ability to spread to intron-free target sites, often assisted by intron-encoded endonucleases that initiate the homing process. Here, leveraging population genomic data from Saccharomyces cerevisiae, Schizosaccharomyces pombe, and Lachancea kluyveri, we expose non-random patterns of genetic diversity in exons that border self-splicing introns. In particular, we show that, in all three species, the density of single nucleotide polymorphisms increases as one approaches a mobile intron. Through multiple lines of evidence we rule out relaxed purifying selection as the cause of uneven nucleotide diversity. Instead, our findings implicate intron mobility as a direct driver of host gene diversity. We discuss two mechanistic scenarios that are consistent with the data: either endonuclease activity and subsequent error-prone repair have left a mutational footprint on the insertion environment of mobile introns or non-random patterns of genetic diversity are caused by exonic co-conversion, which occurs when introns spread to empty target sites via homologous recombination. Importantly, however, we show that exonic co-conversion can only explain diversity gradients near intron-exon boundaries if the conversion template comes from outside the population. In other words, there must be pervasive and ongoing horizontal gene transfer of self-splicing introns into extant fungal populations.
Issue Date: 30-Mar-2017
Date of Acceptance: 7-Feb-2017
URI: http://hdl.handle.net/10044/1/45324
DOI: https://dx.doi.org/10.1534/genetics.116.199059
ISSN: 1943-2631
Publisher: Genetics Society of America
Start Page: 1641
End Page: 1648
Journal / Book Title: Genetics
Volume: 205
Issue: 4
Copyright Statement: Copyright © 2017 Repar and Warnecke Available freely online through the author-supported open access option. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Sponsor/Funder: Imperial College London
Medical Research Council
Funder's Grant Number: Junior Research Fellowship
MC_A658_5TY40
Keywords: gene conversion
genetic diversity
homing endonuclease
mutagenic
self-splicing introns
Developmental Biology
0604 Genetics
Publication Status: Published
Appears in Collections:Clinical Sciences
Molecular Sciences
Faculty of Medicine



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