The role of the Steroidogenesis-Associated gene cyp11a in regulating gonadal development in Hyriopsis cumingii.

The Cyp11a gene is essential for steroid hormone synthesis, which is closely associated with gonadal development. To explore the role of Cyp11a in the gonadal development of Hyriopsis cumingii, we cloned the 2951 bp H. cumingii Cyp11a gene (Hccyp11a), which includes a 2376 bp open reading frame (ORF) encoding 791 amino acids. Phylogenetic analysis revealed that HcCYP11A is closely related to other molluskan homologs. Tissue distribution analysis showed that Hccyp11a was predominantly expressed in the gonad, with significantly higher expression in the ovary compared to the testis (p < 0.01). In juveniles, Hccyp11a expression peaked at 5 months of age. In the gonads of 12-, 24-, and 36-month-old individuals, Hccyp11a consistently exhibited higher expression in females. During ovarian development, Hccyp11a expression was highest at the ovulation stage. In situ hybridization localized Hccyp11a mRNA to the follicular wall and oocytes. RNA interference of female Hccyp11a significantly reduced the expression of Hsd3b and Srd5a1 genes, estradiol (E2) and methyltestosterone (MT) levels. Female H. cumingii were exposed to low (40 ng/L) and high (200 ng/L) concentrations of 17α-methyltestosterone (17α-MT) and 17β-estradiol (17β-E2) for 24 d. Low concentrations of 17α-MT and high concentrations of both 17α-MT and 17β-E2 significantly increased (p < 0.05) Hccyp11a expression. These findings suggest that Hccyp11a is involved in sex hormone synthesis and may regulate gonadal development in H. cumingii through its effects on steroidogenic gene expression and hormone levels.