Molecular cloning and expression pattern of the juvenile hormone epoxide hydrolase gene from the giant freshwater prawn Macrobrachium rosenbergii during larval development and the moult cycle

Juvenile hormone epoxide hydrolases (JHEHs) are regulators of moulting, development and metamorphosis in insects, but we have limited understanding of the roles of these crucial hormonal regulator in crustaceans. In this study, the giant freshwater prawn Macrobrachium rosenbergii was used as a model organism to investigate the role of JHEH in larval development and moulting. We cloned and characterized a JHEH gene from M. rosenbergii (designated as MrJHEH). The full-length cDNA of MrJHEH was 1,682 bp in length, encoding 460 amino acids, and the deduced MrJHEH protein possesses typical features of JHEH family. The phylogenetic analysis revealed that MrJHEH clustered with homologues from crustaceans. Investigation of tissue distribution revealed the abundant expression of MrJHEH in the hepatopancreas. Developmental expression studies showed that the MrJHEH mRNA was expressed throughout the embryo to post-larval stages, with higher expression at late larval stages. Analysis of the moult cycle showed that the expression of MrJHEH mRNA was significantly elevated at the pre-moult stage as compared with the inter-moult level. Both exogenous 20-hydroxyecdysone (20E) injection and eyestalk ablation (ESA) significantly induced the transcription of MrJHEH in cephalothoraxes. These data suggest that MrJHEH is indispensable for the regulation of larval development and ecdysteroidogenesis of M. rosenbergii.