Plant Y Chromosome Degeneration Is Retarded by Haploid Purifying Selection
Plant Y Chromosome Degeneration Is Retarded by Haploid Purifying Selection
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DOI：
10.1016/j.cub.2011.07.045
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发表时间：
2011-09-13
期刊：
影响因子：
9.2
通讯作者：
Filatov, Dmitry A.
中科院分区：
文献类型：
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作者：
Chibalina, Margarita V.;Filatov, Dmitry A.
性染色体在许多不同的生物中独立进化了多次[1]。根据目前公认的模型，X和Y染色体由一对常染色体通过一系列倒位进化而来，导致Y染色体上的非重组区(NRY)逐步扩大，从而导致陷入NRY的基因退化[2]。我们的结果表明，植物是这一规律的例外，因为它们独特的生命周期包括二倍体和单倍体世代的变化以及植物配子体中广泛的单倍体基因表达[3]。使用一种新的高通量方法，我们在宽叶西林中发现了400多个新的从X和Y染色体表达的基因，这是一种大约在1000万年前进化出性染色体的植物。与X连锁基因相比，Y连锁基因表现出更快的氨基酸替代积累和表达丧失。这些退化过程在更受限制的基因和可能暴露于单倍体阶段选择的基因中明显不那么明显。这可能解释了为什么植物尽管经历了数百万年的Y染色体退化，仍保留了数百个与Y相关的表达基因，而动物的Y染色体几乎完全退化。
Sex chromosomes evolved many times independently in many different organisms [1]. According to the currently accepted model, X and Y chromosomes evolve from a pair of autosomes via a series of inversions leading to stepwise expansion of a nonrecombining region on the Y chromosome (NRY) and the consequential degeneration of genes trapped in the NRY [2]. Our results suggest that plants represent an exception to this rule as a result of their unique lifecycle that includes alteration of diploid and haploid generations and widespread haploid expression of genes in plant gametophytes [3]. Using a new high-throughput approach, we identified over 400 new genes expressed from X and Y chromosomes in Silene latifolia, a plant that evolved sex chromosomes about 10 million years ago. Y-linked genes show faster accumulation of amino-acid replacements and loss of expression, compared to X-linked genes. These degenerative processes are significantly less pronounced in more constrained genes and genes that are likely exposed to haploid-phase selection. This may explain why plants retain hundreds of expressed Y-linked genes despite millions of years of Y chromosome degeneration, whereas animal Y chromosomes are almost completely degenerate.