Molecular cloning, characterization and expression analysis of gonadal P450 aromatase in the half-smooth tongue-sole, Cynoglossus semilaevis

Cytochrome P450 aromatase (P450arom) is an enzyme responsible for the conversion of androgen to estrogen. The P450arom plays an important role in gonadal differentiation and sex determination in teleosts. To study the role of gonadal cytochrome P450 aromatase (P450aromA) in sex differentiation, the cDNA was isolated from the ovary of the half-smooth tongue-sole, Cynoglossus semilaevis. The deduced amino acid sequence exhibited high homology with P450arom of other teleosts. Alignment and phylogenetic analysis of the P450arom showed that the tongue sole P450aromA belonged to the gonadal P450arom subfamily. The 5'-flanking region of the P450aromA gene contains two Ad4 binding motifs and a half site of the palindrome sequence of the estrogen-responsive element (the ERE half). P450aromA transcripts were highly abundant in the ovary, less abundant in the testis, but not present in the brain, liver, spleen, kidney, muscle, skin, heart, head kidney, gill, intestine, or eyes by RT-PCR. The P450aromA mRNA increased with gonad development, but was less abundant in the testis compare to the ovary in all phases. Highly abundant P450aromA was detected in the female ovary, but was less abundant in the testis in neo-males obtained by methyltestosterone or temperature treatment. These results imply that P450aromA may be involved in gonadal development and sex differentiation in the tongue sole.