Molecular and transcriptional characterization of GTHs and mPRα during ovarian maturation in rock bream Oplegnathus fasciatus.

The membrane progestin receptor α (mPRα) plays an important role in the regulation of oocyte meiotic maturation in fish. However, the endocrine regulation of multiple spawning in fish with asynchronous ovarian development remains to be determined. We identified four genes (FSHβ, LHβ, CGα and mPRα) that are widely expressed in both the reproductive and non-reproductive tissues of rock bream Oplegnathus fasciatus and examined their expression during ovarian maturation. The level of FSHβ transcripts in the pituitary remained high during vitellogenic stages, when the plasma levels of estradiol-17β reached maximum levels and oocyte development was stimulated. LHβ expression in the pituitary and ovary reached maximum levels during oocyte maturation when the plasma levels of testosterone also reached a maximum. A significant correlation between mPRα transcript levels and the gonadosomatic index was observed during vitellogenesis and final maturation. Brain gonadotropin (FSHβ and LHβ) and mPRα were continuously expressed at different stages of ovarian development. The dynamic and diverse nature of gonadotropins and mPRα gene expression patterns suggests that these genes might jointly regulate ovarian development and maturation through the brain-pituitary-ovary axis in the rock bream endocrine system.