Effects of X-linkage and sex-biased gene expression on the rate of adaptive protein evolution in Drosophila
Effects of X-linkage and sex-biased gene expression on the rate of adaptive protein evolution in Drosophila
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DOI：
10.1093/molbev/msn111
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发表时间：
2008-08-01
影响因子：
10.7
通讯作者：
Parsch, John
中科院分区：
文献类型：
--
作者：
Baines, John F.;Sawyer, Stanley A.;Parsch, John
果蝇蛋白质编码基因的多态性和分化模式表明，物种之间相当一部分氨基酸差异可归因于正选择，并且具有性别偏向表达的基因，即主要在一种性别中表达的基因，具有特别高的适应性进化率。然而，之前的研究仅限于常染色体性别偏见基因，因此并没有提供作用于整个基因组性别偏见基因的进化力量的完整图景。为了确定X连锁对性别偏向基因进化的影响，我们调查了45个X连锁基因的DNA序列多态性和分歧，其中17个具有男性偏向表达，13个具有女性偏向表达，以及15个在两性中表达相同。使用单位点和多位点测试进行选择，我们在两组性别偏向基因中发现了适应性进化的证据。对于 X 连锁的雄性基因来说，适应性进化的信号尤其强烈。与 91 个常染色体基因的数据比较揭示了“fast-X”效应，其中 X 连锁基因的适应性进化速率高于常染色体基因。这种效应对于偏向男性的基因来说最为强烈，但在其他群体中也可以看到。对编码序列差异的全基因组分析（解释了性别偏向表达）也发现了雄性偏向和无偏向基因的 fast-X 效应，表明隐性有益突变在适应中发挥着重要作用。
Patterns of polymorphism and divergence in Drosophila protein-coding genes suggest that a considerable fraction of amino acid differences between species can be attributed to positive selection and that genes with sex-biased expression, that is, those expressed predominantly in one sex, have especially high rates of adaptive evolution. Previous studies, however, have been restricted to autosomal sex-biased genes and, thus, do not provide a complete picture of the evolutionary forces acting on sex-biased genes across the genome. To determine the effects of X-linkage on sex-biased gene evolution, we surveyed DNA sequence polymorphism and divergence in 45 X-linked genes, including 17 with male-biased expression, 13 with female-biased expression, and 15 with equal expression in the 2 sexes. Using both single- and multilocus tests for selection, we found evidence for adaptive evolution in both groups of sex-biased genes. The signal of adaptive evolution was particularly strong for X-linked male-biased genes. A comparison with data from 91 autosomal genes revealed a "fast-X" effect, in which the rate of adaptive evolution was greater for X-linked than for autosomal genes. This effect was strongest for male-biased genes but could be seen in the other groups as well. A genome-wide analysis of coding sequence divergence that accounted for sex-biased expression also uncovered a fast-X effect for male-biased and unbiased genes, suggesting that recessive beneficial mutations play an important role in adaptation.