Evidence that positive selection drives Y-chromosome degeneration in Drosophila miranda
Evidence that positive selection drives Y-chromosome degeneration in Drosophila miranda
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DOI：
10.1038/ng1347
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发表时间：
2004-05-01
期刊：
影响因子：
30.8
通讯作者：
Bachtrog, D
中科院分区：
文献类型：
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作者：
Bachtrog, D
为什么Y染色体的功能位点如此之少？进化理论预测Y染色体退化是因为它们缺乏遗传重组（1）。正（2）和负（1）选择模型都被用来解释这种退化，因为两者都可以导致非重组Y染色体上连锁有害突变的反复固定。为了区分这些模型，我调查了果蝇米兰达最近形成的新Y染色体的核苷酸变异沿着37 kb的模式。这条染色体上的核苷酸变异水平比基因组的高度重组部分低30倍。阳性和阴性选择模型都可以导致变异性水平降低，但它们对突变频谱的影响不同。使用合并模拟，我表明，新Y染色体上的核苷酸变异的模式是不可能的有害突变模型（包括背景选择和穆勒的棘轮），但预计在最近的积极选择。这些结果暗示正选择是驱动Y染色体退化的重要力量;在少数位点的适应，可能增加男性健身，发生在该染色体上的大多数其他基因的成本。
Why does the Y chromosome harbor so few functional loci? Evolutionary theory predicts that Y chromosomes degenerate because they lack genetic recombination(1). Both positive(2) and negative(1) selection models have been invoked to explain this degeneration, as both can result in the recurrent fixation of linked deleterious mutations on a nonrecombining Y chromosome. To distinguish between these models, I investigated patterns of nucleotide variability along 37 kb of the recently formed neo-Y chromosome in Drosophila miranda. Levels of nucleotide variability on this chromosome are 30 times lower than in highly recombining portions of the genome. Both positive and negative selection models can result in reduced variability levels, but their effects on the frequency spectrum of mutations differ. Using coalescent simulations, I show that the patterns of nucleotide variability on the neo-Y chromosome are unlikely under deleterious mutation models (including background selection and Muller's ratchet) but are expected under recent positive selection. These results implicate positive selection as an important force driving the degeneration of Y chromosomes; adaptation at a few loci, possibly increasing male fitness, occurs at the cost of most other genes on this chromosome.