Polyubiquitin is required for growth, development and pathogenicity in the rice blast fungus Magnaporthe oryzae.
Protein ubiquitination, which is highly selective, regulates many important biological processes including cellular differentiation and pathogenesis in eukaryotic cells. Here, we integrated pharmacological, molecular and proteomic approaches to explore the role of ubiquitination in Magnaporthe oryzae, the leading fungal disease of rice world-wide. Inhibition of ubiquitin-mediated proteolysis using the 26S proteasome inhibitor, Bortezomib, significantly attenuated conidia germination, appressorium formation and pathogenicity in M. oryzae. Gene expression analysis revealed that many genes associated with protein ubiquitination were developmentally regulated during conidia germination. Only a few, including a polyubiquitin encoding gene, MGG_01282, were more abundantly expressed during appressorium formation and under nitrogen starvation. Targeted gene deletion of MGG_01282, in addition to a significant reduction in protein ubiquitination as determined by immuno blot assays, resulted in pleiotropic effects on M. oryzae including reduced growth and sporulation, abnormal conidia morphology, reduced germination and appressorium formation, and the inability to cause disease. Mutants were also defective in sexual development and were female sterile. Using mass spectrometry, we identified 63 candidate polyubiquitinated proteins under nitrogen starvation, which included overrepresentation of proteins involved in translation, transport and protein modification. Our study suggests that ubiquitination of target proteins plays an important role in nutrient assimilation, development and pathogenicity of M. oryzae.
Center for Integrated Fungal Research, Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina, United States of America.
Yeonyee
Y
Oh
William L
WL
Franck
Sang-Oh
SO
Han
Angela
A
Shows
Emine
E
Gokce
David C
DC
Muddiman
Ralph A
RA
Dean
D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D016000:Cluster Analysis; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D015966:Gene Expression Regulation, Fungal; D018525:Germination / Q000235:genetics; D020082:Magnaporthe / Q000235:genetics* / Q000254:growth & development* / Q000472:pathogenicity; D009154:Mutation; D009584:Nitrogen / Q000378:metabolism; D012275:Oryza / Q000382:microbiology*; D010935:Plant Diseases / Q000382:microbiology*; D025821:Polyubiquitin / Q000235:genetics* / Q000378:metabolism; D061988:Proteasome Inhibitors / Q000494:pharmacology; D059748:Proteolysis / Q000187:drug effects; D040901:Proteomics; D011719:Pyrazines / Q000494:pharmacology; D054875:Ubiquitination
D001897:Boronic Acids; D005656:Fungal Proteins; D061988:Proteasome Inhibitors; D011719:Pyrazines; D025821:Polyubiquitin; D000069286:Bortezomib; D009584:Nitrogen