To address the roles of Dmrt1, Foxl2 and aromatase in sex differentiationof Southern catfish, the cDNA sequences of these genes were isolated from the gonads.Dmrt1a and Dmrt1b were found to be expressed in the gonads, being higherin the testis. A low expression level of Dmrt1b was also detected in the intestine andkidney of the male. Foxl2 was found to be expressed extensively in the brain (B),pituitary (P), gill and gonads (G), with the highest level in the ovary, indicating the possibleinvolvement of Foxl2 in the B-P-G axis. Cyp19b was found to be expressed inthe brain, spleen and gonads, while Cyp19a was only expressed in the gonads andspleen. All-female Southern catfish fry were treated with fadrozole (F), tamoxifen (TAM)and 17b-estradiol (E2) respectively, from 5 to 25days after hatching (dah). The expression levels of these genes were measured at 65 dah. Inthe F, TAM and F+TAM treated groups, Dmrt1a and Dmrt1b were up-regulated in the gonad whereas Foxl2 and Cyp19a were down-regulated,while the expression of Cyp19b in the gonad remained unchanged. Furthermore,down-regulation of Foxl2 and Cyp19b was also detected in the brain. In theE2 treated group, Dmrt1a and Dmrt1b were down-regulated toan undetectable level in the gonad whereas Foxl2 and Cyp19b were up-regulated in the brain. Consistent with the observed changes in the expressions of thesegenes, 56%, 70% and 80% sex reversed male individuals were obtained in the F, TAM andF+TAM treated groups, respectively. These results indicate the significant roles ofDmrt1, Foxl2 and Cyp19 in the sex differentiation of Southerncatfish.
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