Extreme heterogeneity in sex chromosome differentiation and dosage compensation in livebearers
Extreme heterogeneity in sex chromosome differentiation and dosage compensation in livebearers
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DOI：
10.1073/pnas.1905298116
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发表时间：
2019-09-17
影响因子：
11.1
通讯作者：
Mank, Judith E.
中科院分区：
文献类型：
--
作者：
Darolti, Iulia;Wright, Alison E.;Mank, Judith E.
一旦X和Y染色体之间的重组停止，性染色体就开始分化并过渡到异形。虽然性染色体分化的程度在不同支系之间存在显著差异，但关于支系内性染色体分化的差异却知之甚少。在这里，我们结合了全基因组和转录组测序数据来描述包括孔雀鱼在内的栖息着的沼泽地区的性染色体系统的结构和保守性。我们发现Poecilia reetata XY系统比之前认为的要古老得多，不仅与它的姊妹物种Poecilia wingei共享，而且与大约2000万年前分裂的Poecilia picta共享。尽管有共同的祖先，但我们发现在这些物种中，性染色体的比例和Y染色体的衰退程度都存在着极端的异质性。网纹侧耳和翼侧侧耳的性染色体在很大程度上是同态的，前者的重组持续了相当大的一部分。然而，黑斑潜蝇的性染色体是完全不重组的，并且具有惊人的异形性。值得注意的是，Picta祖先Y染色体的深度退化被该物种功能染色体范围的剂量补偿的进化所抵消，这在硬骨鱼中是以前没有观察到的。我们的结果为性染色体进化和剂量补偿的初始阶段提供了重要的洞察力。
Once recombination is halted between the X and Y chromosomes, sex chromosomes begin to differentiate and transition to heteromorphism. While there is a remarkable variation across clades in the degree of sex chromosome divergence, far less is known about the variation in sex chromosome differentiation within clades. Here, we combined whole-genome and transcriptome sequencing data to characterize the structure and conservation of sex chromosome systems across Poeciliidae, the livebearing Glade that includes guppies. We found that the Poecilia reticulata XY system is much older than previously thought, being shared not only with its sister species, Poecilia wingei, but also with Poecilia picta, which diverged roughly 20 million years ago. Despite the shared ancestry, we uncovered an extreme heterogeneity across these species in the proportion of the sex chromosome with suppressed recombination, and the degree of Y chromosome decay. The sex chromosomes in P. reticulata and P. wingei are largely homomorphic, with recombination in the former persisting over a substantial fraction. However, the sex chromosomes in P. picta are completely nonrecombining and strikingly heteromorphic. Remarkably, the profound degradation of the ancestral Y chromosome in P. picta is counterbalanced by the evolution of functional chromosome-wide dosage compensation in this species, which has not been previously observed in teleost fish. Our results offer important insight into the initial stages of sex chromosome evolution and dosage compensation.