Genome rearrangements and pervasive meiotic drive cause hybrid infertility in fission yeast.
Bottom Line: Hybrid sterility is one of the earliest postzygotic isolating mechanisms to evolve between two recently diverged species.Two of these driving loci are linked by a chromosomal translocation and thus constitute a novel type of paired meiotic drive complex.Our study reveals how quickly multiple barriers to fertility can arise.
Affiliation: Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States.Show MeSH
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Mentions: Our analyses of recombination also revealed a surprising genetic linkage between leu1 and ade6 in Sk/Sp hybrids, despite the fact that these genes are located on chromosomes 2 and 3, respectively, in both species (Figure 4B, Figure 4—figure supplement 2). We speculated that there was a reciprocal translocation between Sk chromosomes 2 and 3, relative to Sp. If such a translocation included essential genes, it would render gametes with non-parental chromosome combinations of the affected arms inviable; this inviability would also create the semblance of genetic linkage between the two chromosomes. Consistent with this possibility, we found using Southern blot analyses that essential genes (alr2 and SPCP1E11.08) had swapped chromosome locations between Sk and Sp (Figure 4B,C; Kim et al., 2010). We partially assembled the Sk genome to map the translocation junctions to position 676,281 on Sp chromosome 2 and 1,932,034 on Sp chromosome 3. We verified the translocation junctions via PCR (Figure 4—figure supplement 5). Analyses of synteny in two outgroup species (S. octosporus and S. cryophilus; Rhind et al., 2011) showed that the translocation occurred in the Sk lineage. The translocation appears to have resulted from a crossover between a Tf transposon found in Sk on chromosome 2 (corresponding to a single Tf transposon LTR in Sp) and a Tf transposon unique to Sk on chromosome 3.
Affiliation: Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, United States.