An eclosion hormone-like gene participates in the molting process of Palaemonid shrimp Exopalaemon carinicauda

Abstract

Molting behavior is an important physiological process related to metamorphosis, growth, and reproduction in crustaceans. Previous studies indicated that the molting process was controlled by 20-hydroxyecdysone (20E) and upstream hormones, peptides, and environmental factors, which regulate 20E function. Eclosion hormone (EH) in insect is a kind of neuropeptide that is regulated by 20E and triggers ecdysis behavior at the end of molting process. However, the function of eclosion hormone gene during the molting process in crustaceans is still largely unknown. In the present study, an eclosion hormone-like gene EcEHL was identified from Exopalaemon carinicauda. The deduced amino acid sequence of EcEHL contained a signal peptide, a typical eclosion domain, and six conserved cysteine residues forming three putative disulfide bonds. EcEHL was predominantly expressed in the epidermis, gill, and eyestalk of shrimp. In situ hybridization analysis showed that EcEHL transcripts were localized in gill cells and in medulla externa X-organ, medulla terminalis X-organ, sinus gland, and lamina ganglionaris of eyestalks. During the molting process of shrimp, EcEHL showed the highest expression level in shrimp at the premolt stage. The expression level of EcEHL in shrimp at mid premolt stage was up-regulated by injection of exogenous 20E. Silencing of EcEHL using double-stranded RNA delayed both the molting process and ecdysis rate of E. carinicauda. Furthermore, injection of exogenous 20E to shrimp at mid premolt stage (D2) could remarkably speed up the molting process and also raise the ecdysis rate of E. carinicauda. The results revealed that EcEHL might participate in the molting process of shrimp and its expression was regulated by 20E. These data will help us to understand the molecular mechanism of molting in crustacean.