Evolution of the Degenerated Y-Chromosome of the Swamp Guppy, Micropoecilia picta.
Evolution of the Degenerated Y-Chromosome of the Swamp Guppy, Micropoecilia picta.
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DOI：
10.3390/cells11071118
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发表时间：
2022-03-25
期刊：
影响因子：
6
通讯作者：
Schartl M
中科院分区：
文献类型：
--
作者：
Nanda I;Schories S;Simeonov I;Adolfi MC;Du K;Steinlein C;Alsheimer M;Haaf T;Schartl M
孔雀鱼显着的颜色性别二态性使其成为性连锁特征和性染色体进化的典型研究对象。孔雀鱼（Poecilia reticulata）的X和Y染色体均具有遗传活性和同态性，具有较大的同源部分和较小的性别特异性区域。这一特征被认为是模仿性染色体进化的初始阶段。在相关的恩德勒孔雀鱼和奥罗普切孔雀鱼（P. wingei、P. obscura）中也记录了类似的情况，表明该组中 Y 的共同起源。最近对沼泽孔雀鱼 (Micropoecilia. picta) 进行的一项分子研究报告称，Y 上的 SNP 密度较低，表明 Y 染色体退化。我们对M. picta进行了一系列细胞学研究，结果表明Y染色体与X染色体相比相当小，并且积累了高含量的异染色质。此外，Y 染色体在着丝粒区域周围显示 CpG 簇方面很突出。这些细胞学发现清楚地表明，斑马鱼的Y染色体确实是高度退化的。粗线期性母细胞中 SYCP3 和 MLH1 的免疫染色显示，Y 的很大一部分仍然与 X 相关。特定的 MLH1 热点位点在相关 XY 结构的远端持续标记。这些结果揭示了 M. picta 严重退化的 Y 染色体上重组伪常染色体区域的一个里程碑。对雌性进行激素治疗后发现，出人意料的是，斑彩鳅中没有 Y 连锁的性拮抗颜色基因。所有这些与孔雀鱼组的差异表明，与性染色体进化相关的轨迹并不平行。
The conspicuous colour sexual dimorphism of guppies has made them paradigmatic study objects for sex-linked traits and sex chromosome evolution. Both the X- and Y-chromosomes of the common guppy (Poecilia reticulata) are genetically active and homomorphic, with a large homologous part and a small sex specific region. This feature is considered to emulate the initial stage of sex chromosome evolution. A similar situation has been documented in the related Endler’s and Oropuche guppies (P. wingei, P. obscura) indicating a common origin of the Y in this group. A recent molecular study in the swamp guppy (Micropoecilia. picta) reported a low SNP density on the Y, indicating Y-chromosome deterioration. We performed a series of cytological studies on M. picta to show that the Y-chromosome is quite small compared to the X and has accumulated a high content of heterochromatin. Furthermore, the Y-chromosome stands out in displaying CpG clusters around the centromeric region. These cytological findings evidently illustrate that the Y-chromosome in M. picta is indeed highly degenerated. Immunostaining for SYCP3 and MLH1 in pachytene meiocytes revealed that a substantial part of the Y remains associated with the X. A specific MLH1 hotspot site was persistently marked at the distal end of the associated XY structure. These results unveil a landmark of a recombining pseudoautosomal region on the otherwise strongly degenerated Y chromosome of M. picta. Hormone treatments of females revealed that, unexpectedly, no sexually antagonistic color gene is Y-linked in M. picta. All these differences to the Poecilia group of guppies indicate that the trajectories associated with the evolution of sex chromosomes are not in parallel.
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