Expression of a wheat β-1,3-glucanase in Pichia pastoris and its inhibitory effect on fungi commonly associated with wheat kernel

beta-1,3-glucanases, the plant PR-2 family of pathogenesis-related (PR) proteins, can be constitutively expressed and induced in wheat crop to enhance its anti-fungal pathogen defense. This study aimed to investigate the inhibitory effect of wheat beta-1,3-glucanase on fungi most commonly associated with wheat kernel. A beta-1,3-glucanase from wheat was successfully expressed in Pichia pastoris X-33 and its biochemical and antifungal properties were characterized herein. The molecular weight of recombinant beta-1,3-glucanase is approximately 33 kDa. beta-1,3-glucanase displays optimal activity at pH 6.5, remaining relatively high at pH 5.5-8.0. The optimal reaction temperature of beta-1,3-glucanase is 50 degrees C, retaining approximately 84.0% residual activity after heat-treated at 50 degrees C for 1 h. The steady-state kinetic parameters of beta-1,3-glucanase against laminarin was determined and the K-m and V-max were 1.32 +/- 0.20 mg/ml and 96.4 +/- 4.4 U mg(-1) protein, respectively. The inhibitory effect of purified beta-1,3-glucanase against the seven fungi commonly associated with wheat kernel was assessed in vitro. beta-1,3-glucanase exerted differential inhibitory effects on hyphal growth of Fusarium graminearurn, Alternaria sp., A. glaucus, A. flavus, A. niger, and Penicillium sp. Spore formation and mycelial morphology of Alternaria sp., A. flavus, and A. niger were significantly affected by beta-1,3-glucanase (1U). The present results would help elucidate the mechanism underlying the inhibition of wheat beta-1,3-glucanases on pathogens.