Molecular Cloning and Characterization of a Putative Ecdysis-triggering Hormone Receptor (ETHR) Gene from Macrobrachium nipponense

Ecdysis-triggering hormone receptor (ETHR) is a G protein-coupled receptor that plays crucial physiological roles in arthropod molting. In this study, the full-length complementary DNA of a putative ETHR gene of Macrobrachium nipponense (ETHR) was cloned and its expression examined. The transcript encoded 390 amino acids, including seven transmembrane domains and specific functional sites that are highly conserved among arthropod species. ETHR expression was examined in 10 different tissue types and was most highly expressed in brain tissue, indicating that the brain is the major functional site of ETHR activity. ETHR displayed relatively low expression levels during early embryonic development (cleavage, blastula, and gastrula stages) and then gradually increased from the nauplius stage, with a significant increase in the zoea stage. ETHR levels significantly increased in the brain and epidermis during the premolt stage. Eyestalk ablation induced significant upregulation of ETHR expression after 3 d. Downregulation of ETHR expression by double-stranded RNA-mediated RNA interference reduced the molting frequency of M. nipponense to almost half of that in the control group. This study suggests that the putative ETHR plays an important role in facilitating the molting process in M. nipponense.