Expression profile of a degenerating neo-Y chromosome in Drosophila
Expression profile of a degenerating neo-Y chromosome in Drosophila
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DOI：
10.1016/j.cub.2006.07.053
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发表时间：
2006-09-05
期刊：
影响因子：
9.2
通讯作者：
Bachtrog, Doris
中科院分区：
文献类型：
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作者：
Bachtrog, Doris
背景资料：基因贫乏，退化的Y染色体已经从普通的常染色体反复演变，但鲜为人知的是沉默的过程中，大多数基因在不断发展的Y.结果：在这里，我量化的相对表达水平的58个基因对最近形成的新的性染色体的果蝇米兰达，为了测试竞争模型的基因失活的新发展的Y染色体（新-Y）。虽然D.米兰达仍然包含其原始基因的大部分，大多数表现出蛋白质进化的加速速率，并且许多包含移码或无义突变。除了三个基因外，所有这些基因在neo-X和neo-Y染色体上显示出显著不同的表达水平，所有基因中有80%在neo-Y染色体上以较低的水平表达。neo-Y上许多基因的下调似乎是随机发生的，无论氨基酸取代的积累水平如何，也不管基因是否产生功能蛋白。此外，相邻的基因表现出相当大的异质性的基因表达水平，反对染色质结构介导的变化，在基因表达levels.Conclusions的观察：我的研究结果表明，转录失活退化Y连锁基因是一个偶然的突变积累的副产品，而不是由选择保持在功能位点的表达或下调适应不良的基因从新的Y。因此，在neo-Y上观察到的大多数突变可能对适应性产生有害影响，并由于非重组染色体上自然选择效率降低而积累，而不是中性或适应性的。
Background: Gene-poor, degenerate Y chromosomes have evolved repeatedly from ordinary autosomes, but little is known about the processes that silence most genes on an evolving Y.Results: Here, I quantify relative expression levels of 58 gene pairs on the recently formed neo-sex chromosomes of Drosophila miranda, in order to test competing models of gene inactivation on its newly evolving Y chromosome (the neo-Y). Although the neo-Y of D. miranda still contains the majority of its original genes, most exhibit an accelerated rate of protein evolution, and many contain frameshift or nonsense mutations. All but three of these genes show significantly different levels of expression from the neo-X and neo-Y chromosome, with similar to 80% of all genes being expressed at lower levels from the neo-Y. The downregulation of many genes on the neo-Y appears to occur randomly, regardless of the level of accumulation of amino acid substitutions or whether the gene produces a functional protein. In addition, adjacent genes show considerable heterogeneity in levels of gene expression, an observation that argues against chromatin-structure-mediated changes in gene expression levels.Conclusions: My results suggest that transcriptional inactivation of degenerating Y linked genes is an accidental by-product of mutation accumulation, and not driven by selection to either maintain expression at functional loci or downregulate maladapted genes from the neo-Y. Thus, most mutations observed on the neo-Y are likely to have deleterious effects on fitness and accumulate as a result of the reduced efficiency of natural selection on a nonrecombining chromosome, rather than neutrally or adaptively.