Cloning and functional identification of chitinase gene 1 in swimming crab Portunus trituberculatus

Abstract:

Chitinase plays an important role in the molting, digestion, and pathogen defense of Portunus trituberculatus. However, little is known about the P. trituberculatus chitinase genes. To understand the P. trituberculatus chitinase gene family, we investigated its chitinase gene 1 (PtCht1). PtCht1 has a total cDNA of 2220 bp and encodes for 583 amino acids. We found that PtCht1 exhibited the basic structure and contained the conserved sequence of the chitinase GH18 family genes of crustaceans. The phylogenetic tree showed that Cht1 of P. trituberculatus was clustered with Cht1 of other species such as Scylla serrata, with 92.80% homology. Therefore, we concluded that PtCht1 is a Group1 gene of the crustacean GH18 family. Further, it is the first P. trituberculatus gene in this classification. Additionally, the results of whole tissue expression analysis showed that PtCht1 was highly expressed in the hepatopancreas, and the expression level in the hepatopancreas during the inter-molt was significantly higher than in the pre-molt and post-molt (P < 0.05). After low salinity stress treatment, the expression level of PtCht1 gene in hepatopancreas rapidly rose to the peak at 3 h (2.72-fold); in the gill, except for 12 h, the expression level of PtCht1 gene was significantly up-regulated (P < 0.05), up to 9.96-fold. Our results show that the PtCht1 gene can participate in the digestion of foods containing chitin and plays a significant role in the regulation of osmotic pressure. Thus, our study is a landmark study in Group1 gene research of the chitinase GH18 family of P. trituberculatus. To conclude, the gene function studies of PtCht1 provide new clues for analyzing the effect of salinity on the growth of P. trituberculatus.