Functional Characterization of the Novel Laminaripentaose-Producing β-1,3-Glucanase MoGluB and Its Biocontrol of Magnaporthe oryzae

Fungal cell wall synthesizing enzymes or remodeling enzymes represent key factors for the interaction of plant pathogen and antifungal agents, which are regarded as potential biocontrol agents. In this study, a novel endo-β-1,3-glucanase from Magnaporthe oryzae was expressed and characterized. The expression of MoGluB was significantly upregulated after 2 days of liquid culture and 48 h after infection, indicating that it may be involved in cell wall reconstitution. Purified MoGluB exhibited high activity on insoluble β-glucans, with a specific activity of 8.18 U/mg toward yeast glucan at pH 9.0 and 50 °C. MoGluB hydrolyzed pachymaran and yeast glucan into oligosaccharides dominated by laminaripentaose, suggesting that it is an endo-β-1,3-glucanase. Incubation of 8 μg of MoGluB with 106 spores/mL resulted in the inhibition of conidial germination and appressorium formation of M. oryzae, illustrating effective biocontrol activity. Hydrolysates of pachymaran induced the expression of defense genes restricting M. oryzae infection in rice plants, indicating an immunostimulatory effect of MoGluB hydrolysates.