Transcriptomics analysis provides new insights into the ovarian lipid droplet formation and lipid deposition in Plectropomus leopardus.

The leopard coral grouper (Plectropomus leopardus), an increasingly important species in marine aquaculture, has garnered significant research interest due to its high market value. Despite extensive research on ovarian growth and development in fish, the molecular mechanisms governing lipid droplet formation and lipid deposition in P. leopardus remain poorly understood. In this study, we conducted transcriptomic analyses of P. leopardus ovaries at three developmental stages: primary growth (PG), pre-vitellogenesis (PV), and mid-vitellogenesis (MV). A total of 534,847,090 raw reads were obtained from nine cDNA libraries, leading to the identification of 19,155 genes with 13,817 genes expressed at all stages. Differential analysis showed that 1012, 2609, and 4039 genes were up-regulated, while 168, 277, and 577 genes were down-regulated in the three comparisons, respectively. Functional enrichment analyses highlighting the critical roles of differentially expressed genes (DEGs) in lipid transport (such as fatp1, fatp4, fatp6, apoeb, lpl and fabps), fatty acid metabolism (such as elovl6, acsl1, dgat2 and gpat4) and phospholipid metabolism (such as ept1, chka and pla2g15). These findings underscore their contribution to lipid droplet formation and deposition. Furthermore, key signaling pathways, including Wnt, mTOR, PPAR and PI3K/Akt, were implicated in regulating these processes. The reliability of the RNA-seq data was confirmed through qPCR validation of 10 lipid-related genes. Based on these results, we propose a model for lipid droplet formation and lipid deposition during ovarian development in P. leopardus. This study advances our understanding of ovarian development in P. leopardus and provides a foundation for future research on marine fish reproduction, with potential applications in species conservation and aquaculture management.