The antifungal activity of a thaumatin-like protein from oyster Crassostrea gigas
Keywords:Crassostrea gigas, Thaumatin-like protein, Antifungal activity, Immune response
In the present study, a thaumatin-like protein (CgTLP) was identified from the oyster Crassostrea gigas. The full-length cDNA of CgTLP was of 913 bp with a 5’ untranslated regions (UTR) of 98 bp, a 3’ UTR of 80 bp, and an open reading frame (ORF) of 735 bp encoding a polypeptide of 244 residues. The CgTLP gene was expressed ubiquitously in mantle, gonad, hemocytes, hepatopancreas, gill, and adductor muscle with the higher expression levels in adductor muscle, hemocytes, and hepatopancreas. Immunofluorescence assay indicated that CgTLP was mainly distributed in the cytoplasm of hemocytes. The mRNA expression levels of CgTLP in hemocytes were significantly up-regulated after the stimulations with mannan (13.69-fold, p < 0.05), Pichia pastoris (8.85-fold, p < 0.05) and polyinosinic-polycytidylic acid (3.62-fold, p < 0.05), but did not change significantly after stimulations with lipopolysaccharide, peptidoglycan, and Vibrio splendidus. The recombinant CgTLP protein (rCgTLP) significantly inhibited the proliferation of P. pastoris (p < 0.05), while no inhibition towards Staphylococcus aureus and V. splendidus. rCgTLP also displayed obvious β-1,3-glucanase activity, while no enzymatic activity towards chitin. These results collectively indicated that CgTLP was a homologue of TLP, which might play a vital role in defensing against fungal infection in C. gigas.