Lovell John T, Williamson Robert J, Wright Stephen I, McKay John K, Sharbel Timothy F
Department of Integrative Biology, University of Texas at Austin, Austin, TX, United States of America.
Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada.
PLoS Genet. 2017 Jan 9;13(1):e1006550. doi: 10.1371/journal.pgen.1006550. eCollection 2017 Jan.
Asexual populations experience weaker responses to natural selection, which causes deleterious mutations to accumulate over time. Additionally, stochastic loss of individuals free of deleterious mutations can lead to an irreversible increase in mutational load in asexuals (the "click" in Muller's Ratchet). Here we report on the genomic divergence and distribution of mutations across eight sympatric pairs of sexual and apomictic (asexual) Boechera (Brassicaceae) genotypes. We show that apomicts harbor a greater number of derived mutations than sympatric sexual genotypes. Furthermore, in phylogenetically constrained sites that are subject to contemporary purifying selection, the ancestral, conserved allele is more likely to be retained in sexuals than apomicts. These results indicate that apomictic lineages accumulate mutations at otherwise conserved sites more often than sexuals, and support the conclusion that deleterious mutation accumulation can be a powerful force in the evolution of asexual higher plants.
无性繁殖群体对自然选择的响应较弱，这导致有害突变随时间积累。此外，不含有害突变的个体的随机丢失会导致无性繁殖群体的突变负荷不可逆增加（穆勒棘轮效应中的“棘轮咔嗒声”）。在此，我们报告了八对同域分布的有性和无融合生殖（无性）的岩生庭荠属（十字花科）基因型之间的基因组差异及突变分布。我们发现，无融合生殖类型比同域分布的有性基因型含有更多的衍生突变。此外，在受到当代纯化选择的系统发育受限位点，有性生殖类型比无融合生殖类型更有可能保留祖先的保守等位基因。这些结果表明，无融合生殖谱系比有性生殖谱系更频繁地在其他保守位点积累突变，并支持有害突变积累可能是高等植物无性进化中一股强大力量的结论。
