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Abstract：
Sex chromosome turnover is the transition between sex chromosomes and autosomes. Although many cases have been reported in poikilothermic vertebrates, their evolutionary causes and genetic mechanisms remain unclear. In this study, we report multiple transitions between the Y chromosome and autosome in the Japanese Tago\'s brown frog complex. Using chromosome banding and molecular analyses (sex-linked and autosomal single nucleotide polymorphisms, SNPs, from the nuclear genome), we investigated the frogs of geographic populations ranging from northern to southern Japan of two species, Rana tagoi and Rana sakuraii (2n = 26). Particularly, the Chiba populations of East Japan and Akita populations of North Japan in R. tagoi have been, for the first time, investigated here. As a result, we identified three different sex chromosomes, namely chromosomes 3, 7, and 13, in the populations of the two species. Furthermore, we found that the transition between the Y chromosome (chromosome 7) and autosome was repeated through hybridization between two or three different populations belonging to the two species, followed by restricted chromosome introgression. These dynamic sex chromosome turnovers represent the first such findings in vertebrates and imply that speciation associated with inter- or intraspecific hybridization plays an important role in sex chromosome turnover in frogs.
摘要：
性染色体周转是性染色体和常染色体之间的过渡。尽管在变热脊椎动物中已经报道了许多病例，它们的进化原因和遗传机制仍不清楚。在这项研究中,我们报道了日本Tago棕色青蛙复合体中Y染色体和常染色体之间的多重转换。使用染色体带和分子分析（性连锁和常染色体单核苷酸多态性，SNPs,来自核基因组)，我们调查了从日本北部到南部的两种地理种群的青蛙，Ranatagoi和Ranasakuraii（2n=26）。特别是,东日本的千叶人口和北日本的秋田人口在R.tagoi一直是，第一次,在这里调查。因此,我们发现了三种不同的性别染色体,在这两个物种的种群中，即染色体3、7和13。此外，我们发现Y染色体（染色体7）和常染色体之间的转换是通过两个或三个属于两个物种的不同种群之间的杂交重复的，其次是限制性染色体渗入。这些动态的性染色体周转代表了脊椎动物中的第一个此类发现，并暗示与种间或种内杂交相关的物种形成在青蛙的性染色体周转中起着重要作用。
