Variation of the meiotic recombination landscape and properties over a broad evolutionary distance in yeasts

Abstract

Meiotic recombination is a major factor of genome evolution, deeply characterized in only a few model species, notably the yeast Saccharomyces cerevisiae. Consequently, little is known about variations of its properties across species. In this respect, we explored the recombination landscape of Lachancea kluyveri, a protoploid yeast species that diverged from the Saccharomyces genus more than 100 million years ago and we found striking differences with S. cerevisiae. These variations include a lower recombination rate, a higher frequency of chromosomes segregating without any crossover and the absence of recombination on the chromosome arm containing the sex locus. In addition, although well conserved within the Saccharomyces clade, the S. cerevisiae recombination hotspots are not conserved over a broader evolutionary distance. Finally and strikingly, we found evidence of frequent reversal of commitment to meiosis, resulting in return to mitotic growth after allele shuffling. Identification of this major but underestimated evolutionary phenomenon illustrates the relevance of exploring non-model species.

Recent admixture between species of the fungal pathogenHistoplasma

“…), and within genomes (e.g., Brion et al. ), these calculations should be considered a qualitative estimate of the recency of gene flow, and not a precise estimate of the time of admixture. Regardless of the precise age of admixture, the large size of the haplotypes indicates that hybridization occurred recently and rules out the possibility of retention of ancestral polymorphism (i.e., segregating variation that predates speciation).…”

Genome wide analysis of meiotic recombination in yeast: For a few SNPs more

“…Another study in a series of mlh3 point mutants showed a genome wide increase in non‐crossovers that supports a structural role for this complex in deciding the fate of meiotic recombination intermediates 56. Furthermore, recent studies in alternate yeast models such as Lachancea kluyveri hybrid have shed light on the significant inter‐specific variation in meiotic recombination frequency 57. Whole genome analysis of L. kluyveri meiotic spores revealed lower crossover frequencies compared to S. cerevisiae , a high proportion of non‐exchange chromosomes as well as a high frequency of 4:0 conversion tracts in the hybrid indicative of the role of abortive meiosis in genome evolution 57, 58.…”

“…Furthermore, recent studies in alternate yeast models such as Lachancea kluyveri hybrid have shed light on the significant inter‐specific variation in meiotic recombination frequency 57. Whole genome analysis of L. kluyveri meiotic spores revealed lower crossover frequencies compared to S. cerevisiae , a high proportion of non‐exchange chromosomes as well as a high frequency of 4:0 conversion tracts in the hybrid indicative of the role of abortive meiosis in genome evolution 57, 58. These above mentioned studies are a few examples of the new insights into meiotic recombination mechanisms using genome wide recombination mapping methods.…”

André Goffeau's imprinting on second generation yeast “genomologists”

“…The study of meiotic recombination provided another good example of the relevance of exploring nonmodel species because little is known about variations of its properties across non‐ Saccharomyces species. Recombination rate is much lower in L. kluyveri than in S. cerevisiae , and recombination hotspots are not conserved between the two species (Brion et al, ). Another striking feature is the absence of recombination on the chromosome arm containing the MAT locus in L. kluyveri .…”

“…In fact, analysis revealed a relic of a 1‐Mb introgressed region with a different recombination and substitution regime compared with the rest of the genome. Interestingly, the gene expression landscape showed that genes located in this introgressed region tend to be less transcribed, have a higher variability between isolates, and are less involved in transcriptional networks (Brion et al, ).…”