Mitochondrial fission protein MoFis1 mediates conidiation and is required for full virulence of the rice blast fungus Magnaporthe oryzae

The mitochondrial fission protein Fis1 regulates yeast mitochondrial fission and is required for ethanol-induced mitochondrial fragmentation and apoptosis. To examine the function of Fis1 in a plant pathogenic fungus, we cloned the MoFIS1 gene, a homolog of Saccharomyces cerevisiae FIS1, from Magnaporthe oryzae and characterized its function by targeted gene deletion and mutant phenotypic analysis. MoFIS1 deletion mutants were unaltered in conidial germination, appressorium formation, and mating tests, but were severely defective in colony growth, conidiation, virulence on rice and barley, growth under nitrogen and glucose deficiency, and growth under osmotic stress. Blast lesions on rice leaves caused by the ΔMofis1 strain were significantly reduced, were non-proliferating, and were less coalesced as compared to the highly coalesced and proliferating lesions resulting from infection with the wild-type strain. The defects in growth, conidiation, and virulence of the mutant were restored in a complementation strain of ΔMofis1. A MoFis1-GFP fusion protein co-localized with Mitotracker red in mitochondria. These results show that MoFIS1 encodes a mitochondrial protein that regulates fungal growth, conidiation, and virulence in M. oryzae.