Characterization of vasa in the gonads of different ploidy fish.

Vasa is an essential gene for germ cell development belonging to the DEAD-box family. In this study, we comparatively analyzed the expression characteristics of vasa in diploids, triploids, and tetraploids. The sequences showed high similarity among these fish and other vertebrates, with characteristic domains. Tissue expression analysis revealed that vasa was expressed exclusively in the gonad of different ploidy fishes. During embryogenesis, vasa expression was lower in diploid than in triploid and tetraploid fish, caused by doubling of the genome of tetraploids and abnormal gonads in the triploid fish. In adults, vasa mRNA levels were significantly lower in the testes of sterile triploid fish compared with fertile diploids and tetraploids. In the ovaries, triploid fish showed consistently high expression from the non-breeding season to the breeding season. Immunohistochemistry and western blotting results also supported the abnormal expression of vasa in triploid gonads. This study demonstrates, for the first time, that fish of different ploidy exhibit different expression patterns of vasa that contribute to the differentiation of gonadal development.