Identification and Characterization of Hdh-FMRF2 Gene in Pacific Abalone and Its Possible Role in Reproduction and Larva Development

FMRFamide-related peptides are neuropeptides involved in a wide range of biological processes, including reproduction and larval development. To characterize the involvement of FMRFamide in the reproduction and larval development of Pacific abalone Haliotis discus hannai, an FMRFamide cDNA (Hdh-FMRF2) was cloned from the cerebral ganglion (CG). Fluorescence in situ hybridization and qRT-PCR were performed for functional characterization. The Hdh-FMRF2 cDNA encoded 204 deduced amino acids that contained a putative signal peptide and four FaRP domains. The major population of Hdh-FMRF2 neuronal cell bodies was localized in the cortex of CG. Hdh-FMRF2 mRNA expression was significantly upregulated in CG during the mature stage of gonadal development and effective accumulative temperature (EAT) exposed abalone in both sexes. In the induced spawning event, Hdh-FMRF2 expression was significantly upregulated during spawning in males. However, no upregulation was observed in females, suggesting Hdh-FMRF2 might inhibit gamete release in female abalone. These results revealed Hdh-FMRF2 as a reproduction related peptide. Furthermore, mRNA expression in larval development suggested that this peptide was also involved in larval development during development of Pacific abalone. Collectively, this study provides evidence of possible involvement of an FMRFamide neuropeptide in the reproduction and larval development of Pacific abalone.