Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4.
Proc Natl Acad Sci U S A. 2018 May 29;115(22):E5046-E5055. doi: 10.1073/pnas.1801040115. Epub 2018 May 14.
By altering the dynamics of DNA replication and repair, alternative ploidy states may experience different rates and types of new mutations, leading to divergent evolutionary outcomes. We report a direct comparison of the genome-wide spectrum of spontaneous mutations arising in haploids and diploids following a mutation-accumulation experiment in the budding yeast Characterizing the number, types, locations, and effects of thousands of mutations revealed that haploids were more prone to single-nucleotide mutations (SNMs) and mitochondrial mutations, while larger structural changes were more common in diploids. Mutations were more likely to be detrimental in diploids, even after accounting for the large impact of structural changes, contrary to the prediction that mutations would have weaker effects, due to masking, in diploids. Haploidy is expected to reduce the opportunity for conservative DNA repair involving homologous chromosomes, increasing the insertion-deletion rate, but we found little support for this idea. Instead, haploids were more susceptible to SNMs in late-replicating genomic regions, resulting in a ploidy difference in the spectrum of substitutions. In diploids, we detect mutation rate variation among chromosomes in association with centromere location, a finding that is supported by published polymorphism data. Diploids are not simply doubled haploids; instead, our results predict that the spectrum of spontaneous mutations will substantially shape the dynamics of genome evolution in haploid and diploid populations.
通过改变 DNA 复制和修复的动态，不同的倍性状态可能经历不同的新突变率和类型，从而导致不同的进化结果。我们报告了在芽殖酵母中进行的突变积累实验后，单倍体和二倍体中自发突变的全基因组谱的直接比较。 对数千个突变的数量、类型、位置和影响进行特征分析表明，单倍体更容易发生单核苷酸突变（SNMs）和线粒体突变，而二倍体中更常见的是较大的结构变化。即使考虑到结构变化的巨大影响，突变在二倍体中也更有可能是有害的，这与突变在二倍体中由于屏蔽而效应较弱的预测相反。单倍体预计会减少涉及同源染色体的保守 DNA 修复的机会，增加插入缺失率，但我们几乎没有发现支持这一观点的证据。相反，单倍体更容易受到晚期复制基因组区域中 SNMs 的影响，导致替换谱中的倍性差异。在二倍体中，我们检测到染色体之间的突变率变化与着丝粒位置有关，这一发现得到了已发表的多态性数据的支持。二倍体不是简单的双倍单倍体；相反，我们的结果预测，自发突变的频谱将极大地塑造单倍体和二倍体群体中基因组进化的动态。
