Molecular identification of dmrt2 and dmrt5 and effect of sex steroids on their expressions in Chlamys nobilis

The dmrt (double-sex and mab-3-related transcription factor) gene family, characterized by a highly conserved zinc finger-like DNA-binding motif known as the DM domain, plays important roles in sex differentiation and sexual development. To better understand the role of dmrt on the sexual development in Chlamys nobilis, 1183 bp encoding cDNAs for dmrt2 and 2362 bp encoding cDNAs for dmrt5 have been cloned and functionally characterized. Dmrt2 and dmrt5 display significant homologies to DMRT2 cluster and DMRT5 cluster, respectively, and exhibit all the typical features of dmrt family. Real-time PCR analyses show that dmrt2 was expressed exclusively in gonads and dmrt5 distributed widely in tissues. Both of them were expressed at all developmental stages examined and peaked at blastula stage. Dmrt2 expression peaked at resting stage in the female gametogenetic cycle, and mature stage in male gonadal development. Dmrt5 expression peaked at resting stage in the female gametogenetic cycle and no significant differences were observed in male gonadal development. Expression of dmrt2 and dmrt5 of C. nobilis at spawning stage was upregulated by different concentration of MT (17α-methyltestosterone) injected into the male and E2 (17β-estradiol) injected into the female, at different time after treatment, and even different duration of function. These results implied that dmrt2 is more likely to be involved in playing a functional role in male gonadal development or maintenance of gonadal function than dmrt5 and dmrt5 may be involved in other biological processes besides gonadal development in C. nobilis.