Kuroda Masamichi, Shibata Kiko, Fujimoto Takafumi, Murakami Masaru, Yamaha Etsuro, Arai Katsutoshi
Faculty of Fisheries Sciences, Hokkaido University, Hakodate, Japan.
Department of Ocean and Fisheries Sciences, Faculty of Bioindustry, Tokyo University of Agriculture, Abashiri, Japan.
Cytogenet Genome Res. 2021;161(3-4):178-186. doi: 10.1159/000515107. Epub 2021 May 10.
In dojo loach (Misgurnus anguillicaudatus), although most wild types are gonochoristic diploids that are genetically differentiated into 2 groups, A and B, clonal lineages appear in certain localities. Clonal loaches have been considered to have hybrid origins between the 2 groups by a series of genetic studies. In this study, using FISH with a newly developed probe (ManDra-A), we identified 26 (1 pair of metacentric and 12 pairs of telocentric chromosomes) of 50 diploid chromosomes in contemporary wild-type group A loach. In contrast, ManDra-A signals were not detected on metacentric chromosomes derived from the ancestral group A of clonal loach. The FISH results clearly showed the presence of certain differentiations in metacentric chromosomes between ancestral and contemporary group A loach. Two-color FISH with ManDra-A and group B-specific ManDra (renamed ManDra-B) probes reconfirmed the hybrid origin of clones by identifying chromosomes from both groups A and B in metaphases. Our results showed the hybrid origin of clonally reproducing fish and the possibility that chromosomal differentiation between ancestral and contemporary fish can affect gametogenesis. In meiotic spermatocytes of sex-reversed clones, ManDra-A, and not ManDra-B, signals were detected in 12 out of 50 bivalents. Thus, the results further support the previous conclusion that clonal gametogenesis was assured by pairing between sister chromosomes duplicated from each ancestral chromosome from group A or B. Our study deepens the knowledge about the association between clonality and hybridity in unisexual vertebrates.
在泥鳅（Misgurnus anguillicaudatus）中，虽然大多数野生型是雌雄异体的二倍体，在基因上分为A和B两组，但在某些地区出现了克隆谱系。通过一系列遗传学研究，克隆泥鳅被认为具有这两组之间的杂交起源。在本研究中，我们使用一种新开发的探针（ManDra-A）进行荧光原位杂交（FISH），在当代野生型A组泥鳅的50条二倍体染色体中鉴定出了26条（1对中着丝粒染色体和12对端着丝粒染色体）。相比之下，在克隆泥鳅的祖先A组的中着丝粒染色体上未检测到ManDra-A信号。FISH结果清楚地表明，祖先A组泥鳅和当代A组泥鳅的中着丝粒染色体存在某些差异。用ManDra-A和B组特异性ManDra（重新命名为ManDra-B）探针进行双色FISH，通过在中期鉴定出A组和B组的染色体，再次证实了克隆的杂交起源。我们的结果表明了克隆繁殖鱼类的杂交起源，以及祖先鱼和当代鱼之间的染色体分化可能影响配子发生的可能性。在性反转克隆的减数分裂精母细胞中，在50个二价体中的12个中检测到了ManDra-A信号，而不是ManDra-B信号。因此，这些结果进一步支持了先前的结论，即克隆配子发生是通过来自A组或B组每个祖先染色体复制的姐妹染色体之间的配对来确保的。我们的研究加深了对单性脊椎动物克隆性与杂交性之间关联的认识。
