Correlation between Kisspeptin 2 and its Receptors in Blue Gourami Fish (Trichogaster trichopterus), and its Role in Reproduction

Expression of kisspeptin 2 (Kiss2) and Kiss receptors (Kiss1r [GPR54] and Kiss2r) was examined in blue gourami fish. The degree of similarity between the cDNA sequences of Kiss2 and Kiss1r in blue gourami compared to various other fish species was low, whereas there was little variation in Kiss2r sequences among the species. To investigate the expression of Kiss2, Kiss1r, and Kiss2r in the female blue gourami brain, quantitative PCR amplification was used to determine relative mRNA levels in juvenile and mature females before vitellogenesis and during vitellogenesis, respectively. Results showed significant differences in their transcription levels, and a model is proposed for regulation of vitellogenesis by Kiss2 in blue gourami.
Graphical Abstract: Gonadotropic brain-pituitary-gonadal (BPG) axis and hypothalamic-pituitary-gonadal (HPG) axis. BR, brain; PI, pituitary gland; HT, hypothalamus; Kiss, kisspeptin; KissR, Kiss receptor; GnRH, gonadotropin-releasing hormone; FSH, follicle-stimulating hormone; E2, estradiol. The HPG axis is suggested to be influenced by the interaction of these hormones.