Sequence and expression of a cDNA encoding both pituitary adenylate cyclase activating polypeptide and growth hormone-releasing hormone in grouper (Epinephelus coioides).

Both pituitary adenylate cyclase activating polypeptide PACAP and growth hormone-releasing hormone GHRH belong to the vasoactive intestinal polypeptide- glucagon-secretin family. They are encoded on the same gene in vertebrates (birds, amphibian, fish). Although the gene encoding PACAP and GHRH has been cloned in other fish species, characterization of this gene in the commercially important grouper (Epinephelus coioides) has not been previously reported. In this study, the GHRH/PACAP cDNA was cloned from grouper hypothalamic tissue. Two cDNA variants of the GHRH/PACAP precursor gene were identified as a result of alternative splicing, a long form encoding both PACAP and GHRH and a short form encoding only PACAP. Both the long and the short forms of the GHRH/PACAP precursor cDNA were identified in grouper 22 issues as well as expression in embryos and larvae by semi-quantitative RT-PCR detection. PACAP / GHRH precursor mRNA was expressed at a high level in the central nervous system than in several peripheral tissues. The data presented here provide the report of PACAP/GHRH mRNA expression in eye and gill tissues in fish. PACAP/GHRH mRNA was expressed in grouper embryo and all larval stages examined and was expressed at a high level starting on neurula stage onwards. The result suggests that PACAP/GHRH had an important role in the development of embryos and larvae, especially in neurula appearance stage.