Chitosan inhibits septin?mediated plant infection by the rice blast fungus <i>Magnaporthe oryzae</i> in a protein kinase C and Nox1 NADPH oxidase?dependent manner

Chitosan is a partially deacetylated linear polysaccharide composed of ?-1,4-linked units d-glucosamine and N-acetyl glucosamine. As well as structural component fungal cell walls, chitosan potent antifungal agent. However, the mode action poorly understood. Here, we report that effective for control rice blast disease. application impairs growth fungus Magnaporthe oryzae has pronounced effect on appressorium-mediated plant infection. inhibits septin-mediated F-actin remodelling at appressorium pore, thereby preventing repolarization infection cell. causes plasma membrane permeabilization M. affects NADPH oxidase-dependent synthesis reactive oxygen species, essential septin ring formation pathogenicity. We further show toxicity to requires protein kinase C-dependent wall integrity pathway, Mps1 mitogen-activated Nox1 oxidase. A conditionally lethal, analogue (PP1)-sensitive mutant Pkc1 remediated in presence chitosan, while ?nox1 mutants increase their glucan : chitin ratio, rendering them resistant chitosan. Taken together, our data fungicide which disrupts function