Nuclear estrogen receptors differentially regulate the cyp19a1a promoter in Trachinotus blochii

Estrogen signaling plays a central role in teleost ovarian differentiation, but whether nuclear estrogen receptors (Esrs) contribute to E 2 -responsive regulation of gonadal cyp19a1a remains unclear. In this study, we characterized three nuclear estrogen receptor paralogs Esr1, Esr2a, and Esr2b in golden pompano ( Trachinotus blochii ) and examined their potential roles in 17β-estradiol (E 2 )-responsive regulation of cyp19a1a . Re-analysis of gonadal RNA-seq data showed that esr1 , esr2a , esr2b , and cyp19a1a were coordinately upregulated and exhibited female-biased expression during early gonadal differentiation, while RT-qPCR confirmed their developmental upregulation in female gonads. Sequence and structural bioinformatic analyses demonstrated conserved DNA-binding and ligand-binding domains across the three Esr proteins. Comparative promoter prediction identified putative ESR-family binding motifs in the upstream regions of cyp19a1a in all teleost species examined, including two candidate motifs in the T. blochii cyp19a1a promoter. Dual-luciferase reporter assays showed that only Esr1 and Esr2b could significantly increase cyp19a1a promoter activity and E 2 further enhanced promoter activity in cells expressing each of the three Esrs. These results indicate that the three Esr paralogs diverge in their basal trans-activation capacity but exhibit overlapping E 2 -dependent regulatory capacities. Furthermore, dietary E 2 exposure for 7 days increased plasma E 2 levels and gonadal cyp19a1a expression in genetically male juveniles without altering esr1 , esr2a , or esr2b transcript abundance. Collectively, these findings reveal subtype-specific E 2 -responsive regulation of the cyp19a1a promoter and support a potential positive regulatory link between nuclear Esr signaling and gonadal aromatase expression during early ovarian differentiation in marine teleosts.