PDF(Pubmed)
Abstract：
Sex chromosomes display remarkable diversity and variability among vertebrates. Compared with research on the X/Y and Z/W chromosomes, which have long evolutionary histories in mammals and birds, studies on the sex chromosomes at early evolutionary stages are limited. Here, we precisely assembled the genomes of homozygous XX female and YY male Lanzhou catfish (Silurus lanzhouensis) derived from an artificial gynogenetic family and a self-fertilized family, respectively. Chromosome 24 (Chr24) was identified as the sex chromosome based on resequencing data. Comparative analysis of the X and Y chromosomes showed an approximate 320 kb Y-specific region with a Y-specific duplicate of anti-Mullerian hormone type II receptor (amhr2y), which is consistent with findings in 2 other Silurus species but on different chromosomes (Chr24 of Silurus meridionalis and Chr5 of Silurus asotus). Deficiency of amhr2y resulted in male-to-female sex reversal, indicating that amhr2y plays a male-determining role in S. lanzhouensis. Phylogenetic analysis and comparative genomics revealed that the common sex-determining gene amhr2y was initially translocated to Chr24 of the Silurus ancestor along with the expansion of transposable elements. Chr24 was maintained as the sex chromosome in S. meridionalis and S. lanzhouensis, whereas a sex-determining region transition triggered sex chromosome turnover from Chr24 to Chr5 in S. asotus. Additionally, gene duplication, translocation, and degeneration were observed in the Y-specific regions of Silurus species. These findings present a clear case for the early evolutionary trajectory of sex chromosomes, including sex-determining gene origin, repeat sequence expansion, gene gathering and degeneration in sex-determining region, and sex chromosome turnover.
摘要：
性染色体在脊椎动物中表现出明显的多样性和变异性。与X/Y和Z/W染色体的研讨比拟，在哺乳动物和鸟类中有着悠久的进化史，对进化早期性染色体的研究是有限的。这里,我们精确地组装了纯合XX雌性和YY雄性兰州鲶鱼（Siluruslanzouensis）的基因组，它们来自一个人工雌核发育家族和一个自我受精家族，分别。根据重测序数据，将染色体24（Chr24）鉴定为性染色体。X和Y染色体的比较分析显示，大约有320kb的Y特异性区域，具有抗苗勒管激素II型受体（amhr2y）的Y特异性重复，这与其他两个Silurus物种中的发现一致，但在不同的染色体上（子午线的Chr24和子午线的Chr5）。缺乏amhr2y导致男性对女性的性别逆转，表明amhr2y在兰州S.lanzhouensis中起男性决定作用。系统发育分析和比较基因组学表明，随着转座因子的扩展，常见的性别决定基因amhr2y最初易位到Silurus祖先的Chr24。Chr24在子午线和兰州线中保持为性染色体，而一个性别决定区的转变触发了性染色体从Chr24到Chr5的转换。此外,基因复制，易位,在Silurus物种的Y特异性区域观察到退化。这些发现为性染色体的早期进化轨迹提供了一个明确的例子，包括性别决定基因起源,重复序列扩展，性别决定区的基因聚集和退化，和性染色体更新。
