Center for Information Biology, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka 411-8540, Japan.
Department of Genetics, SOKENDAI, 1111 Yata, Mishima, Shizuoka 411-8540, Japan.
Nat Commun. 2016 Nov 29;7:13659. doi: 10.1038/ncomms13659.
Y chromosomes often degenerate via the accumulation of pseudogenes and transposable elements. By contrast, little is known about X-chromosome degeneration. Here we compare the pseudogenization process between genes on the neo-sex chromosomes in Drosophila miranda and their autosomal orthologues in closely related species. The pseudogenization rate on the neo-X is much lower than the rate on the neo-Y, but appears to be higher than the rate on the orthologous autosome in D. pseudoobscura. Genes under less functional constraint and/or genes with male-biased expression tend to become pseudogenes on the neo-X, indicating the accumulation of slightly deleterious mutations and the feminization of the neo-X. We also find a weak trend that the genes with female-benefit/male-detriment effects identified in D. melanogaster are pseudogenized on the neo-X, implying the masculinization of the neo-X. These observations suggest that both X and Y chromosomes can degenerate due to a complex suite of evolutionary forces.
Y 染色体通常通过假基因和转座元件的积累而退化。相比之下，关于 X 染色体退化的了解甚少。在这里，我们比较了在果蝇 Miranda 的新性染色体上的基因和与其在亲缘关系密切的物种中的常染色体同源基因之间的假基因化过程。新 X 染色体上的假基因化率远低于新 Y 染色体上的假基因化率，但似乎高于 D. pseudoobscura 中同源常染色体上的假基因化率。受功能约束较小的基因和/或具有雄性偏性表达的基因往往会在新 X 染色体上成为假基因，这表明积累了轻微有害突变和新 X 染色体的雌性化。我们还发现一个微弱的趋势，即在 D. melanogaster 中鉴定出的具有雌性受益/雄性损害效应的基因在新 X 染色体上被假基因化，这意味着新 X 染色体的雄性化。这些观察结果表明，X 和 Y 染色体都可能由于一系列复杂的进化力量而退化。
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