Chromosomal Rearrangements as a Major Mechanism in the Onset of Reproductive Isolation in Saccharomyces cerevisiae

Abstract

Summary Understanding the molecular basis of how reproductive isolation evolves between individuals from the same species offers valuable insight into patterns of genetic differentiation as well as the onset of speciation [1, 2]. The yeast Saccharomyces cerevisiae constitutes an ideal model partly due to its vast ecological range, high level of genetic diversity [3–6] and laboratory amendable sexual reproduction. Between S. cerevisiae and its sibling species in the Saccharomyces sensu stricto complex, reproductive isolation acts post-zygotically and could be attributed to chromosomal rearrangements [7], cyto-nuclear incompatibility [8, 9] and anti-recombination [10, 11]; although the implication of these mechanisms at the incipient stage of speciation remains unclear due to further divergence in the nascent species. Recently, several studies assessed the onset of intraspecific reproductive isolation in S. cerevisiae by evaluating the effect of the mismatch repair system [12–14] or by fostering incipient speciation using the same initial genetic background [15–18]. Nevertheless, the overall genetic diversity within this species was largely overlooked and no systematic evaluation has been performed. Here, we carried out the first species-wide survey for post-zygotic reproductive isolation in S. cerevisiae. We crossed 60 natural isolates sampled from diverse niches with the reference strain S288c, and identified 16 cases of reproductive isolation with reduced offspring viabilities ranging from 44% to 86%. Using different mapping strategies, we identified reciprocal translocations in a large fraction of all isolates surveyed, indicating that large-scale chromosomal rearrangements might play a major role to the onset of reproductive isolation in this species.

de novo assembly and population genomic survey of natural yeast isolates with the Oxford Nanopore MinION sequencer

“…Among the detected events, one translocation detected between chromosomes 5 and 14 in the ABH isolate and another translocation between chromosomes 7 and 12 in the AVB isolate have already been described and confirmed in a reproductive isolation study in S. cerevisiae [35]. A deeper investigation of our assemblies highlighted the presence of full-length Ty transposons at some junctions of the translocation events.…”

Species-wide Genetic Incompatibility Analysis Identifies Immune Genes as Hot Spots of Deleterious Epistasis

“…This type of deleterious, or negative, epistasis has been most prominently studied in interspecific crosses, where the interacting alleles are fixed in the different populations (Maheshwari and Barbash, 2011; Presgraves, 2010; Rieseberg and Blackman, 2010). More recent work has begun to focus on deleterious epistasis within species, where the interacting alleles are polymorphic and segregate in a single intermating population (Corbett-Detig et al, 2013; Hou et al, 2014; Seidel et al, 2008). One can envision a series of evolutionary forces responsible for the emergence of interacting alleles.…”

The Evolution of Orphan Regions in Genomes of a Fungal Pathogen of Wheat

“…Structural changes in chromosomes are linked to key steps in the differentiation of sex chromosomes (2, 3), incipient speciation (4), and the emergence and maintenance of phenotypes (5). Structural variants, in particular inversions, segregating in randomly mating populations have long been thought to underlie key adaptive processes, such as the onset of reproductive isolation or the maintenance of clusters of coadapted genes (6).…”