Comparative survey of coordinated regulation of hypothalamic-pituitary-somatotropic axis in golden pompano (Trachinotus ovatus) and humpback grouper (Cromileptes altivelis)

Hypothalamic-Pituitary-Somatotropic (HPS) axis is the essential endocrine system playing important roles in animal growth. Here, the HPS axis were characterized in golden pompano (Trachinotus ovatus) and humpback grouper (Cromileptes altivelis), two marine cultured tropical teleosts representing fast and slow growth patterns, respectively. Through genomic and transcriptomic survey, 32 and 35 HPS genes were characterized in T. ovatus and C. altivelis. Functional domain and phylogeny revealed their conserved function among teleost lineages, with more ssts and igfbps identified and actively expressed in C. altivelis than in T. ovatus. The regulation of HPS genes responding to external stimuli revealed that T. ovatus HPS genes, including gh, igf1/2, igfbp1a/b, igfbp2b and igfbp5b, were differentially expressed under temperature or starvation challenges, while C. altivelis HPS genes were sensitive to salinity change with sst1.2, ghrhrb, igf1, igf2r, igfbp1a and igfbp5a regulated in brains. Strong interactive connectivity of igfbps was found in both T. ovatus and C. altivelis. Moreover, HPS genes evolved differently between T. ovatus and C. altivelis, and positively selected sites were detected in more C. altivelis HPS genes, like in functional domains of igf1ra and igf1rb. The igf1ra evolved faster than igf1rb in teleosts, which may contribute to their functional divergence. In conclusion, this study represented different regulatory and evolutionary patterns of HPS axis between T. ovatus and C. altivelis, which are vital in regulating their growth and will provide comprehensive insights into the cultivation of T. ovatus and C. altivelis in aquaculture.