P-339 - A dual functional Rhizoctonia solani AA9 lytic polysaccharide monooxygenase: promoting infection and triggering immunity depending on subcellular localization

Lytic polysaccharide monooxygenases (LPMOs) are redox enzymes that oxidatively degrade various polysaccharides, such as cellulose. These enzymes are widely distributed in the genomes of both bacteria and fungi. Although LPMOs are broadly studied for their great potential application in biomass conversion in the past decades, studies related to their roles in infectious processes of plant pathogens are just emerging.

Recently, we identified an AA9 LPMO protein, RsLPMOA, produced by the rice sheath blight pathogen Rhizoctonia solani. RsLPMOA is significantly induced in R. solani within early and late infection stage. It acts as a virulence factor in apoplast to promote infection by hydrolysis cellulose, but acts as an elicitor in intracellular to trigger defense responses in rice. Its elicitor effect was also validated in Arabidopsis and solanaceous species. The elicitor activity of RsLPMOA is dependent on an 88 amino acid peptide region but independent of its monooxygenases activity.

Silencing of RsLPMOA in R. solani severely reduced virulence. Ecotopic expression of RsLPMOA in rice apoplast enhances disease susceptibility, while ecotopic expression of RsLPMOA in rice cytoplasmic enhances disease resistance.

Therefore, our data indicated that RsLPMOA displayed a dual function in promoting rice sheath blight infection and triggering plant immunity depending on its different subcellular localization, thus deepening our understanding of LPMO in plant-microbe interactions.