ENDOCRINE GENE EXPRESSION PATTERNS ASSOCIATED WITH THE OVARIAN MATURATION OF WILD FEMALE LARGEMOUTH BRONZE GUDGEON(COREIUS GUICHENOTI)

Oocyte maturation in fish involves numerous cell signaling cascades, including complex regulation by a set of endocrine/autocrine factors during specific stages of oocyte development. Wild largemouth bronze gudgeon (Coreius guichenoti) in the Yangtze River, which are group-synchronous reproducers, provide an opportunity to characterize the features associated with each emerging stage during the process of ovary development. This study reports the transcriptome profiling analysis of wild largemouth bronze gudgeon (Coreius guichenoti) ovaries at various morphologically diverse stages using the powerful RNA-seq approach. Our RNA-seq analysis identified 11 495 contigs with definite gene description according to the zebrafish genome. Focusing on the endocrine/autocrine signaling pathways involved in oocyte maturation and ovulation, the expression profiles of the genes involved in the sensing cascade and metabolism pathways of various hormones and growth factors, such as prolactin (PRL), follicle-stimulating hormone (FSH), estrogen, prostaglandin E2 (PGE2), growth/differentiation factor 9 (GDF9), activin, and anti-Mllerian hormone (AMH), were analyzed. Our results indicate an overall conservation of the components and transcriptome alterations underlying oocyte maturation in fish and other vertebrate models. The transcriptional profile also suggests that 17, 20-dihydroxy-4-pregnen-3-one and not 11-deoxycorticosteron may be synthesized as the maturation-inducing hormone in largemouth bronze gudgeon. The transcripts of the complete set of genes associated with the primary bile acid synthesis pathway in the fish ovary were also observed. This transcriptome profiling analysis provides valuable information regarding thousands of transcripts involved in the ovulation of wild largemouth bronze gudgeon. Because this fish is a wild group-synchronous spawner, the results obtained in our study also revealed insights into the cascades of endocrine regulatory events underlying fish oocyte maturation.