Establishment of the Y-linked Dmrt1Y as the candidate sex determination gene in spotbanded scat (Selenotoca multifasciata)

Spotbanded scat (Selenotoca multifasciata) has become a valuable marine culturing fish species in the southeast coastal areas of China. Herein, sex-linked markers were developed in spotbanded scat to elucidate its genetic foundation of sex determination. Eighty-four (84) cultured spotbanded scat were randomly chosen and used to screen and test the sex-linked markers. The average weight of the female (249 g, n = 32) is significantly higher than that of the male (212 g, n = 52). The whole genome of a male spotbanded scat was sequenced using next-generation sequencing technology. Phylogenetic analysis showed that spotbanded scat diverged from its closely related species, spotted scat (Scatophagus argus) 13.1 million years ago.Three sex-linked markers (Marker-1, 2 and 3) were obtained in spotbanded scat. Marker-1 and 2 could only amplify 562 bp and 881 bp Dmrt1 specific bands in male fish, while there were no amplified bands in female fish. Marker-3 amplified a single band of 373 bp in all female, and double bands of 373 bp and specific 294 bp in male. Sequence analysis showed that the 294 and 373 bp are Dmrt1 homologous sequences. These results indicate that the spotbanded scat possesses XY sex-determination system (XX females, XY males). Two types of Dmrt1 cDNA sequences were cloned and named Dmrt1X and Dmrt1Y according to their locations on the X and Y chromosomes, respectively. The amino acid (aa) sequences coded by Dmrt1X (309 aa) and Dmrt1Y (305 aa) are highly similar (85.8%). Dmrt1Y mRNA is specifically expressed in testis, with no expression in the ovary. Hence, Dmrt1Y is male-specific and the candidate SD gene. Knowledge of genetic sex determination and the development of sex-linked markers in spotbanded scat, will promote artificial reproduction and breeding in aquaculture.