Glycosyltransferase-like toxin of Burkholderia gladioli strain NGJ1 is a potent antifungal protein with potential for control of sheath blight disease in rice

Abstract

Sheath blight disease caused by the fungal pathogen Rhizoctonia solani poses a significant challenge for sustainable rice cultivation. It is important to develop environmentally friendly measures for its control. Previously, a rice-associated Burkholderia gladioli strain NGJ1 was shown to exhibit mycophagous and antifungal activity on R. solani. Here, we report that a B. gladioli glycosyltransferase-like 1 (BGT1) protein with a canonical D×D (aspartic acid × aspartic acid) motif that is homologous to the glycosyltransferase toxin of different bacteria is encoded in the antibacterial type VI secretion system-encoding gene cluster of NGJ1. The recombinant BGT1 protein purified from Escherichia coli exhibits antifungal activity on R. solani, Magnaporthe oryzae, Fusarium oxysporum, Saccharomyces cerevisiae, and Candida albicans under laboratory conditions. Using a variant of the BGT1 protein (BGT1D168L/D170L), we demonstrate that the D×D motif is important for its antifungal activity. The heterologous expression of native BGT1 but not the BGT1D168L/D170L protein prevents the growth of yeast cells. Moreover, treatment with BGT1 but not BGT1D168L/D170L significantly reduces sheath blight disease severity in rice. BGT1 treatment does not elicit adverse effects on plants. In conclusion, we emphasize that BGT1 protein-based or transgene-based biotechnological interventions can be exploited for effective control of sheath blight disease in rice.