Identification and expression characterization of a novel carboxypeptidase A-like gene (RvCPA) during early developmental stages in the gastropod Rapana venosa (Muricidae)

Abstract

Rapana venosa is an economically important aquaculture species in China. Carboxypeptidases (CPs) A and B (CPA and CPB, respectively) hydrolyze peptides and proteins and play critical roles in the development of the digestive system in animals. In this study, a full-length CPA-like cDNA sequence from R. venosa (RvCPA) was isolated using RACE, and RvCPA mRNA expression levels were analyzed in different tissues and developmental stages by quantitative real-time PCR. Additionally, the expression patterns of RvCPA under different diets were investigated in competent larvae of R. venosa. The full-length cDNA of the RvCPA gene was 1,810 bp and consisted of a 1,296-bp open reading frame (ORF) encoding 431 aa. Phylogenetic analysis revealed high homology of RvCPA with CPs from Biomphalaria glabrata, Pomacea canaliculata, and Ampullaria crossean. Our results showed that RvCPA had higher expression in the salivary gland than in other tissues and that the expression of RvCPA was dramatically increased in the juvenile (postlarval) stage compared with other stages, indicating that functional changes occur in the larval digestive system during the food habit transition. Furthermore, we found that an animal diet could significantly increase the expression of RvCPA, which may suggest that animal diets can promote the development of the digestive system. This information on a novel CP in R. venosa that participates in digestion and is related to the food habit transition may broaden our understanding of digestive system development during metamorphosis in carnivorous gastropods.