MoMon1 is required for vacuolar assembly, conidiogenesis and pathogenicity in the rice blast fungus Magnaporthe oryzae.

Mon1 protein is involved in cytoplasm-to-vacuole trafficking, vacuolar morphology and autophagy, and is required for homotypic vacuole fusion in Saccharomyces cerevisiae. Here we identify MoMON1 from Magnaporthe oryzae as an ortholog of S. cerevisiae MON1, essential for the morphology of the vacuole and vesicle fusion. Target gene deletion of MoMON1 resulted in accumulation of small punctuate vacuoles in the hypha and hypersensitivity to monensin, an antibiotic that blocks intracellular protein transport. The ΔMomon1 mutant exhibited significantly reduced aerial hyphal development and poor conidiation. Conidia of ΔMomon1 were able to differentiate appressoria. However, ΔMomon1 was non-pathogenic on rice leaves, even after wound inoculation. In addition, ΔMomon1 was slightly hypersensitive to Congo red and SDS, but not to cell wall degrading enzymes, suggesting significant alterations in its cell wall. The autophagy process was blocked in the ΔMomon1 mutant. Taken together, our results suggest that MoMON1 has an essential function in vacuolar assembly, autophagy, fungal development and pathogenicity in M. oryzae.