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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Accumulation of slightly deleterious mutations in mitochondrial protein-coding genes of large versus small mammals
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Accumulation of slightly deleterious mutations in mitochondrial protein-coding genes of large versus small mammals

机译：大型和小型哺乳动物线粒体蛋白质编码基因中轻微有害突变的积累

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摘要

After the effective size of a population, N_e, declines, some slightly deleterious amino acid replacements which were initially suppressed by purifying selection become effectively neutral and can reach fixation. Here we investigate this phenomenon for a set of all 13 mitochondrial protein-coding genes from 110 mammalian species. By using body mass as a proxy for N_e, we show that large mammals (i.e., those with low N_e) as compared with small ones (in our sample these are, on average, 369.5 kg and 275 g, respectively) have a 43% higher rate of accumulation of nonsynonymous nu-cleotide substitutions relative to synonymous substitutions, and an 8-40% higher rate of accumulation of radical amino acid substitutions relative to conservative substitutions, depending on the type of amino acid classification. These higher rates result in a 6% greater amino acid dissimilarity between modern species and their most recent reconstructed ancestors in large versus small mammals. Because nonsynonymous substitutions are likely to be more harmful than synonymous substitutions, and radical amino acid substitutions are likely to be more harmful than conservative ones, our results suggest that large mammals experience less efficient purifying selection than small mammals. Furthermore, because in the course of mammalian evolution body size tends to increase and, consequently, N_e tends to decline, evolution of mammals toward large body size may involve accumulation of slightly deleterious mutations in mitochondrial protein-coding genes, which may contribute to decline or extinction of large mammals.
机译：在种群的有效大小N_e减小之后，最初通过纯化选择抑制的一些轻微有害的氨基酸替代实际上变成了中性的，并且可以固定。在这里，我们研究了来自110个哺乳动物物种的所有13个线粒体蛋白质编码基因的这种现象。通过使用体重代替N_e，我们显示大型哺乳动物（即，N_e低的哺乳动物）与小型哺乳动物（在我们的样本中，平均分别为369.5千克和275克）的比例为43％相对于同义取代，非同义核苷酸替代物的累积速率更高，相对于保守取代，自由基氨基酸取代的积累率高8-40％，具体取决于氨基酸分类的类型。这些较高的比率导致大型和小型哺乳动物中现代物种与其最近重建的祖先之间的氨基酸差异增加6％。因为非同义取代可能比同义取代有害，自由基氨基酸取代可能比保守取代更有害，所以我们的结果表明，大型哺乳动物的纯化选择效率不如小型哺乳动物。此外，由于在哺乳动物进化过程中，体重趋于增加，因此N_e趋于减少，因此，哺乳动物向大体重的进化可能涉及线粒体蛋白质编码基因中轻度有害突变的积累，这可能有助于降低或降低大型哺乳动物的灭绝。

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