Characterization of Two Gonadal Genes, zar1 and wt1b, in Hermaphroditic Fish Asian Seabass ().

Zygote arrest-1 (Zar1) and Wilms' tumor 1 (Wt1) play an important role in oogenesis, with the latter also involved in testicular development and gender differentiation. Here, and were identified in Asian seabass (), a hermaphrodite fish, as the valuable model for studying sex differentiation. The cloned cDNA fragments of were 1192 bp, encoding 336 amino acids, and contained a zinc-binding domain, while those of cDNA were 1521 bp, encoding a peptide of 423 amino acids with a Zn finger domain belonging to Wt1b family. RT-qPCR analysis showed that mRNA was exclusively expressed in the ovary, while mRNA was majorly expressed in the gonads in a higher amount in the testis than in the ovary. In situ hybridization results showed that mRNA was mainly concentrated in oogonia and oocytes at early stages in the ovary, but were undetectable in the testis. mRNA was localized not only in gonadal somatic cells (the testis and ovary), but also in female and male germ cells in the early developmental stages, such as those of previtellogenic oocytes, spermatogonia, spermatocytes and spermatids. These results indicated that and possibly play roles in gonadal development. Therefore, the findings of this study will provide a basis for clarifying the mechanism of and in regulating germ cell development and the sex reversal of Asian seabass and even other hermaphroditic species.