Uniparental Inheritance Promotes Adaptive Evolution in Cytoplasmic Genomes
Uniparental Inheritance Promotes Adaptive Evolution in Cytoplasmic Genomes
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DOI：
10.1093/molbev/msw266
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发表时间：
2017-03-01
影响因子：
10.7
通讯作者：
Beekman, Madeleine
中科院分区：
文献类型：
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作者：
Christie, Joshua R.;Beekman, Madeleine
真核生物携带大量无性细胞质基因组（线粒体和质体）。缺乏重组，无性基因组理论上应该会受到适应性进化的损害。然而，经验证据表明，细胞质基因组经历了比理论预测更高水平的适应性进化。在这项研究中，我们使用一个计算模型来显示细胞质基因组的独特生物学特性——特别是它们在宿主细胞中的组织和它们的单亲（母系）遗传——使它们能够进行有效的适应性进化。细胞质基因组的单代遗传减少了不同有益取代之间的竞争（克隆干扰），促进了有益取代的积累。单亲本遗传也有助于对抗有害的细胞质取代，减缓穆勒棘轮。此外，在选择性扫描过程中，单代遗传通常会减少有害替代的基因搭便车现象。总的来说，单亲遗传通过增加相对于有害替代的有益替代水平来促进适应性进化。当我们假设细胞质基因组遗传是双亲遗传时，减少配子体发生（瓶颈）过程中传递的基因组数量有助于适应性进化。然而，当遗传是单代遗传时，适应性进化总是更有效。我们的发现解释了细胞质基因组——尽管它们的无性繁殖模式——可以很容易地进行适应性进化的经验观察。
Eukaryotes carry numerous asexual cytoplasmic genomes (mitochondria and plastids). Lacking recombination, asexual genomes should theoretically suffer from impaired adaptive evolution. Yet, empirical evidence indicates that cytoplasmic genomes experience higher levels of adaptive evolution than predicted by theory. In this study, we use a computational model to show that the unique biology of cytoplasmic genomes-specifically their organization into host cells and their uniparental (maternal) inheritance-enable them to undergo effective adaptive evolution. Uniparental inheritance of cytoplasmic genomes decreases competition between different beneficial substitutions (clonal interference), promoting the accumulation of beneficial substitutions. Uniparental inheritance also facilitates selection against deleterious cytoplasmic substitutions, slowing Muller's ratchet. In addition, uniparental inheritance generally reduces genetic hitchhiking of deleterious substitutions during selective sweeps. Overall, uniparental inheritance promotes adaptive evolution by increasing the level of beneficial substitutions relative to deleterious substitutions. When we assume that cytoplasmic genome inheritance is biparental, decreasing the number of genomes transmitted during gametogenesis (bottleneck) aids adaptive evolution. Nevertheless, adaptive evolution is always more efficient when inheritance is uniparental. Our findings explain empirical observations that cytoplasmic genomes-despite their asexual mode of reproduction-can readily undergo adaptive evolution.