Dynamins are large superfamily GTPase proteins that are involved in various cellular processes including budding of transport vesicles, division of organelles, cytokinesis, and pathogen resistance. Here, we characterized several dynamin-related proteins from the rice blast fungus Magnaporthe oryzae and found that MoDnm1 is required for normal functions, including vegetative growth, conidiogenesis, and full pathogenicity. In addition, we found that MoDnm1 co-localizes with peroxisomes and mitochondria, which is consistent with the conserved role of dynamin proteins. Importantly, MoDnm1-dependent peroxisomal and mitochondrial fission involves functions of mitochondrial fission protein MoFis1 and WD-40 repeat protein MoMdv1. These two proteins display similar cellular functions and subcellular localizations as MoDnm1, and are also required for full pathogenicity. Further studies showed that MoDnm1, MoFis1 and MoMdv1 are in complex to regulate not only peroxisomal and mitochondrial fission, pexophagy and mitophagy progression, but also appressorium function and host penetration. In summary, our studies provide new insights into how MoDnm1 interacts with its partner proteins to mediate peroxisomal and mitochondrial functions and how such regulatory events may link to differentiation and pathogenicity in the rice blast fungus.
The transcription factor MoAP1 has been shown previously to be required for pathogenicity in Magnaporthe oryzae via mediation of the oxidative stress response. In the serial analysis gene expression database, it was found that expression of MoYcp4, a homologue of the Saccharomyces cerevisiae flavodoxin-like protein ScYcp4, was affected by MoAP1. Transcriptional analysis demonstrated that MoYCP4 was significantly up-regulated during conidiation, appressorium formation and infection. The growth rate of a ΔMoycp4 mutant was reduced slightly, but conidial production was increased significantly (more than 10-fold), compared with the wild-type strain. Although the rate of appressorium formation was unaffected, the appressorial turgor was abnormal and the ability to infect rice and barley was reduced, resulting in decreased pathogenicity. In summary, MoYcp4, a target of MoAP1, is involved in the growth, conidiogenesis and pathogenicity of M. oryzae. Our studies provide a comprehensive analysis of flavodoxin-like proteins and will aid in the study of pathogen-related molecular mechanisms.
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