Molecular cloning of multiple chitinase genes in Japanese flounder, Paralichthys olivaceus

Three different chitinase genes (fChi1, fChi2 and fChi3) were identified from Japanese flounder, Paralichthys olivaceus. The deduced amino-acid sequences of flounder chitinases revealed a typical chitinase structure containing a catalytic glyco-18 domain, a hinge region and a chitin binding domain type 2. The fChi1 and fChi2 mRNAs were predominantly expressed in the gastric glands of stomach. In contrast, expression of fChi3 was found in spleen, pancreas, stomach, intestine, liver, kidney and gonads of adult flounder by RT-PCR. The expression level of fChi3 in the adult tissues was below the detection limit of in situ hybridization (ISH) analysis; however, ISH signals were detected in the liver of flounder larvae. These results suggest that fChi1 and fChi2 are acidic chitinases that digest dietary chitin and that fChi3 probably is a macrophage specific chitinase (chitotriosidase) for biodefense and has an important unknown role in the liver during larval stages.