Recurrent Loss of Sex Is Associated with Accumulation of Deleterious Mutations in Oenothera
Recurrent Loss of Sex Is Associated with Accumulation of Deleterious Mutations in Oenothera
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DOI：
10.1093/molbev/msu345
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发表时间：
2015-04-01
影响因子：
10.7
通讯作者：
Johnson, Marc T. J.
中科院分区：
文献类型：
--
作者：
Hollister, Jesse D.;Greiner, Stephan;Johnson, Marc T. J.
有性生殖在真核生物中几乎是普遍的。理论预测，无性真核物种的稀有性部分是由于有害突变的积累以及与无性物种重组和分离受到抑制相关的灭绝风险增加造成的。我们测试了这一预测与一个大型数据集的62个转录组从29种植物属月见草，跨越10个独立的过渡性和功能无性遗传系统称为永久易位杂合性。Illumina短读测序和从头转录组装产生了每个个体平均16.4 Mb的序列。在这里，我们表明，功能无性物种积累更多的有害突变比有性物种使用人口基因组和系统发育分析。在个体水平上，无性物种的杂合性比有性物种高1.8倍。在物种内，我们检测到一个较高比例的非同义多态性相对于同义变异内无性与有性物种相比，表明净化选择的效力降低。无性物种也表现出更大比例的成绩单提前终止密码子。非同义突变的比例增加也呈正相关，有性和无性物种之间的分歧时间，与穆勒的棘轮。物种之间，我们检测到重复增加的比例非同义的无性繁殖的姐妹类群相比，无性繁殖的物种的同义分歧，表明有害突变的积累增加。这些结果证实了性的一个重要优势是它有利于对有害等位基因的选择，这可能有助于解释现存无性物种的缺乏。
Sexual reproduction is nearly universal among eukaryotes. Theory predicts that the rarity of asexual eukaryotic species is in part caused by accumulation of deleterious mutations and heightened extinction risk associated with suppressed recombination and segregation in asexual species. We tested this prediction with a large data set of 62 transcriptomes from 29 species in the plant genus Oenothera, spanning ten independent transitions between sexual and a functionally asexual genetic system called permanent translocation heterozygosity. Illumina short-read sequencing and de novo transcript assembly yielded an average of 16.4 Mb of sequence per individual. Here, we show that functionally asexual species accumulate more deleterious mutations than sexual species using both population genomic and phylogenetic analysis. At an individual level, asexual species exhibited 1.8x higher heterozygosity than sexual species. Within species, we detected a higher proportion of nonsynonymous polymorphism relative to synonymous variation within asexual compared with sexual species, indicating reduced efficacy of purifying selection. Asexual species also exhibited a greater proportion of transcripts with premature stop codons. The increased proportion of nonsynonymous mutations was also positively correlated with divergence time between sexual and asexual species, consistent with Muller's ratchet. Between species, we detected repeated increases in the ratio of nonsynonymous to synonymous divergence in asexual species compared with sexually reproducing sister taxa, indicating increased accumulation of deleterious mutations. These results confirm that an important advantage of sex is that it facilitates selection against deleterious alleles, which might help to explain the dearth of extant asexual species.