Glycosyltransferase-Like Toxin of <i>Burkholderia gladioli</i> Strain NGJ1 Is a Potent Antifungal Protein with Potential for Control of Sheath Blight Disease in Rice

Sheath blight disease caused by the fungal pathogen <i>Rhizoctonia solani</i> poses a significant challenge for sustainable rice cultivation. It is important to develop environmentally friendly measures for its control. Previously, a rice-associated <i>Burkholderia gladioli</i> strain NGJ1 was shown to exhibit mycophagous and antifungal activity on <i>R. solani</i>. Here, we report that a <i>B. gladioli</i> 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 <i>Escherichia coli</i> exhibits antifungal activity on <i>R. solani</i>, <i>Magnaporthe oryzae</i>, <i>Fusarium oxysporum</i>, <i>Saccharomyces cerevisiae</i>, and <i>Candida albicans</i> under laboratory conditions. Using a variant of the BGT1 protein (BGT1^D168L/D170L), we demonstrate that the D×D motif is important for its antifungal activity. The heterologous expression of native BGT1 but not the BGT1^D168L/D170L protein prevents the growth of yeast cells. Moreover, treatment with BGT1 but not BGT1^D168L/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.