Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI.
Ranomics Inc., Toronto, ON, Canada.
Mol Biol Evol. 2019 Feb 1;36(2):412-422. doi: 10.1093/molbev/msy233.
Meiotic recombination comprises crossovers and noncrossovers. Recombination, crossover in particular, shuffles mutations and impacts both the level of genetic polymorphism and the speed of adaptation. In many species, the recombination rate varies across the genome with hot and cold spots. The hotspot paradox hypothesis asserts that recombination hotspots are evolutionarily unstable due to self-destruction. However, the genomic landscape of double-strand breaks (DSBs), which initiate recombination, is evolutionarily conserved among divergent yeast species, casting doubt on the hotspot paradox hypothesis. Nonetheless, because only a subset of DSBs are associated with crossovers, the evolutionary conservation of the crossover landscape could differ from that of DSBs. Here, we investigate this possibility by generating a high-resolution recombination map of the budding yeast Saccharomyces paradoxus through whole-genome sequencing of 50 meiotic tetrads and by comparing this recombination map with that of S. cerevisiae. We observe a 40% lower recombination rate in S. paradoxus than in S. cerevisiae. Compared with the DSB landscape, the crossover landscape is even more conserved. Further analyses indicate that the elevated conservation of the crossover landscape is explained by a near-subtelomeric crossover preference in both yeasts, which we find to be attributable at least in part to crossover interference. We conclude that the yeast crossover landscape is highly conserved and that the evolutionary conservation of this landscape can differ from that of the DSB landscape.
减数分裂重组包括交叉和非交叉。重组，特别是交叉，打乱了突变，影响了遗传多态性的水平和适应的速度。在许多物种中，重组率在基因组中存在热点和冷点的差异。重组热点悖论假说认为，由于自我毁灭，重组热点在进化上是不稳定的。然而，引发重组的双链断裂 (DSB) 的基因组景观在不同的酵母物种中是进化保守的，这对重组热点悖论假说提出了质疑。尽管如此，由于只有一部分 DSB 与交叉有关，因此交叉景观的进化保守性可能与 DSB 不同。在这里，我们通过对 50 个减数分裂四分体进行全基因组测序，生成了出芽酵母 Saccharomyces paradoxus 的高分辨率重组图谱，并将该图谱与酿酒酵母进行了比较，从而研究了这种可能性。我们观察到 S. paradoxus 的重组率比 S. cerevisiae 低 40%。与 DSB 景观相比，交叉景观更加保守。进一步的分析表明，交叉景观的高度保守性可以用两种酵母中近着丝粒的交叉偏好来解释，我们发现这种偏好至少部分归因于交叉干扰。我们得出结论，酵母交叉景观高度保守，并且这种景观的进化保守性可能与 DSB 景观的进化保守性不同。
