Cloning, characterization, and expression analysis of the CHITINASE gene family in Helice tientsinensis

Chitinase is a kind of glycoside hydrolase which is widely distributed in nature and encoded by multiple genes to catalyze the decomposition of chitin, which plays an important role in the molting and pathogen defense of crustaceans. However, the research on chitinase in crustaceans is mainly focused on a few species with economic value. In this study, full-length cDNA sequences of the HtCHT1, HtCHT3 and HtCHT4 genes were cloned from the mudflat crab Helice tientsinensis by RACE, and the sequences were analyzed. The results showed that the full-length 2,229 bp of HtCHT1 gene encoded 627 amino acids, while the full-length 2,191 bp of HtCHT3 gene produced 489 amino acids, and the full-length 3,312 bp of HtCHT4 gene encoded 664 amino acids. Bioinformatics analysis showed that all the obtained chitinase proteins had the glycosyl hydrolase family 18 (GH18) catalytic domain and chitin-binding domain (ChtBD2), furthermore, HtCHT1 and HtCHT4 proteins had signal peptide domains at N-terminal. Phylogenetic analysis showed that different types of chitinase were clustered, and HtCHTs were closely related to chitinases in the Eriocheir sinensis. Expression profile analysis showed that the HtCHT1, HtCHT3 and HtCHT4 were significantly expressed in hepatopancreas. Furthermore, the expression of three genes was significantly up-regulated in hepatopancreas after the Vibrio parahaemolyticus challenge. These results suggested that HtCHT1, HtCHT3 and HtCHT4 were belonged to the CHITINASE gene family in H. tientsinensis and were potentially involved in the antibacterial immune response. This study provides essential information for further research of chitinase in H. tientsinensis and even crustaceans.