Crossing-over in a hypervariable species preferentially occurs in regions of high local similarity

Vladimir B. Seplyarskiy, Maria D. Logacheva, Aleksey A. Penin, Maria A. Baranova, Evgeny V. Leushkin, Natalia V. Demidenko, Anna V. Klepikova, Fyodor A. Kondrashov, Alexey S. Kondrashov, Timothy Y. James

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

Recombination between double-stranded DNA molecules is a key genetic process which occurs in a wide variety of organisms. Usually, crossing-over (CO) occurs during meiosis between genotypes with 98.0-99.9% sequence identity, because within-population nucleotide diversity only rarely exceeds 2%. However, some species are hypervariable and it is unclear how CO can occur between genotypes with less than 90% sequence identity. Here, we study CO in Schizophyllum commune, a hypervariable cosmopolitan basidiomycete mushroom, a frequently encountered decayer of woody substrates. We crossed two haploid individuals, from the United States and from Russia, and obtained genome sequences for their 17 offspring. The average genetic distance between the parents was 14%, making it possible to study CO at very high resolution. We found reduced levels of linkage disequilibrium between loci flanking the CO sites indicating that they are mostly confined to hotspots of recombination. Furthermore, CO events preferentially occurred in regions under stronger negative selection, in particular within exons that showed reduced levels of nucleotide diversity. Apparently, in hypervariable species CO must avoid regions of higher divergence between the recombining genomes due to limitations imposed by the mismatch repair system, with regions under strong negative selection providing the opportunity for recombination. These patterns are opposite to those observed in a number of less variable species indicating that population genomics of hypervariable species may reveal novel biological phenomena.

Original languageEnglish
Pages (from-to)3016-3025
Number of pages10
JournalMolecular Biology and Evolution
Volume31
Issue number11
DOIs
Publication statusPublished - 1 Nov 2014
Externally publishedYes

Keywords

  • hyperpolymorphic
  • negative selection
  • recombination
  • S. Commune

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