Synchronously sexual maturity in hermaphrodite fish as revealed by transcriptome analysis in Plectropomus leopardus

Leopard coral grouper (Plectropomus leopardus) is a type of hermaphrodite fish, but the mechanisms of gonadal development and gametogenesis remain unclear. In the present study, we performed histological observation and transcriptomic analysis during the process of sexual differentiation in P. leopardus. According to the histological results, sexual differentiation was completed at 15 months old, developed synchronously in male and female individuals at 2 years old, and matured synchronously at 3 years old. Comparative transcriptomic analyses showed that the gonadal had differentiated by 15 months old, with enrichment of pathways associated with cell proliferation, transcriptional metabolism, and germline stem cell differentiation. Furthermore, cilium movement and fatty acid anabolism, which are associated with spermatogenesis and oocyte growth, were significantly enriched at 3 years old. In addition, key genes associated with male and female sex differentiation, such as amh, dmrt1, dmrt2a, zp4, sox3, gdf9, and gsdf, were identified by weighted gene co-expression network analysis (WGCNA). Finally, the localization and expression of the key genes amh and sox3 were observed in different cell types within the testes and ovaries, reflecting the development of the testes and ovaries, respectively. All the evidence indicates that P. leopardus is a hermaphrodite and synchronously sexually mature fish. Our study complements the gonadal development patterns of hermaphroditic fish by providing new insights into the molecular mechanisms underlying sexual differentiation and sex change in hermaphroditic groupers.