GnIH/GnIHR REGULATES THE EXPRESSION OF GENES RELATED TO MATING BEHAVIOR IN OVOVIVIPAROUS BLACK ROCKFISH (SEBASTES SCHLEGELII)

As an important economic species of cage culture in the Yellow Sea and Bohai Sea, the teleost Sebastes schlegelii has a unique oviviparous reproduction mode. In recent years, due to the decline of wild resources of S. schlegelii, farmers began to experiment with cage-cultured adult fish as parent for artificial reproduction. However, the quantity and quality of offspring produced by cultured parents were significantly lower than those of wild parents. Research showed that this phenomenon was closely related to the number of mating between male and female parents. Gonadotropin-inhibiting hormone (GnIH) was an important regulator of reproductive endocrinology and reproductive behavior. In order to explore the regulatory effect of GnIH on reproductive behavior in S. schlegelii, the open reading frame (ORF) of gnih/gnihr genes were cloned, tissues expression patterns were detected by qPCR, and gnih neurons in the hypothalamus were localized by in situ hybridization. In order to verify the function of GnIH, intraperitoneal and intraventricular injection of synthetic GnIH-Ⅲ were used to detect the changes of the relative expression levels of genes related to mating behavior and reproductive endocrine, respectively. The results showed that the gnih sequence with an ORF of 537 bp, encoding a protein composed of 178 amino acids. The precursor peptide could be processed into 3 mature peptides. The ORF of gnihr gene is 1452 bp, encoding a G protein-coupled receptors with 483 amino acids. The gnih was most highly expressed in the hypothalamus and located in the hypothalamic preoptic area of small cell body preoptic nucleus (NPO), large cell body preoptic nucleus (PM) and anterior periventricular nucleus (NAPv). And gnihr co-localized with kisspeptin1 and cgnrh genes, which regulated reproductive behavior in the brain. GnIH maturation peptide could bind to GnIHR and activate the downstream CRE signaling pathway. The results of ventricular and intraperitoneal injections showed that GnIH maturation peptide promoted gonadal maturation and triggered mating behavior. This study provided a theoretical basis for the mating induction mechanism of S. schlegelii.