LAUSR

Estradiol treatment during early life stages of tiger puffer Takifugu rubripes induces feminization in genetic males. However, the ovaries in genetic males may revert to testes once estradiol treatment is halted. Therefore studies should investigate molecular mechanisms underlying ovary-to-testis recovery in genetic males after treatment. In the present study, tiger puffer were exposed to 10, and 100 µg/L 17β-estradiol (E2) from 15 to 100 days post-hatching (dph), then gonad phenotypes and expression profiles of six sex-related genes (cyp19a, foxl2, dmrt1, amh, sox9a, and sox9b) were characterized after the exposure. Results showed that both 10 and 100 µg/L E2 induced ovarian development in genetic males at 100 dph. However, all ovaries induced by 10 µg/L E2 first developed into intersexual gonads and subsequently reverted to testes after the exposure. As for treatment of 100 µg/L E2, while the rest of the ovaries maintained morphological stability, percentages of intersexual gonads reached 38%–57%, and none were reverted to testes. Increased mRNA levels of cyp19a, foxl2 and sox9b and decreased mRNA levels of dmrtl, amh, and sox9a were observed during the ovarian development in genetic males. While contrary gene expression profiles were detected during ovary-to-testis transformation. The mRNA levels of all the six genes were increased during the development of intersexual gonads. These results indicated that up-regulation of dmrt1, amh and sox9a is associated with initial ovary-to-intersexual transformation, and suppression of foxl2, cyp19a and sox9b is essential for complete ovary-to-testis recovery in genetic males. This research will help to trace the molecular processes underlying gonadal transformation in teleosts.