Comparative Transcriptome Analysis of the Hypothalamic-Pituitary-Gonadal Axis of Jinhu Grouper ( Epinephelus fuscoguttatus ♀ × Epinephelus tukula ♂) and Tiger Grouper ( Epinephelus fuscoguttatus ).

Jinhu groupers, the hybrid offspring of tiger groupers ( Epinephelus fuscoguttatus ) and potato groupers ( Epinephelus tukula ), have excellent heterosis in fast growth and strong stress resistance. However, compared with the maternal tiger grouper, Jinhu groupers show delayed gonadal development. To explore the interspecific difference in gonadal development, we compared the transcriptomes of brain, pituitary, and gonadal tissues between Jinhu groupers and tiger groupers at 24-months old. In total, 3034 differentially expressed genes (DEGs) were obtained. KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analyses showed that the osteoclast differentiation, oocyte meiosis, and ovarian steroidogenesis may be involved in the difference in gonadal development. Trend analysis showed that the DEGs were mainly related to signal transduction and cell growth and death. Additionally, differences in expression levels of nr4a1 , pgr , dmrta2 , tbx19 , and cyp19a1 may be related to gonadal retardation in Jinhu groupers. A weighted gene co-expression network analysis revealed three modules (i.e., saddlebrown, paleturquoise, and greenyellow) that were significantly related to gonadal development in the brain, pituitary, and gonadal tissues, respectively, of Jinhu groupers and tiger groupers. Network diagrams of the target modules were constructed and the respective hub genes were determined (i.e., cdh6 , col18a1 , and hat1 ). This study provides additional insight into the molecular mechanism underlying ovarian stunting in grouper hybrids.