Polyubiquitin Is Required for Growth, Development and Pathogenicity in the Rice Blast Fungus Magnaporthe oryzae

Abstract

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.

Proteomic profiling of Botrytis cinerea conidial germination

“…They are involved in the adaptation of metabolism by degrading transcriptional regulators (Hershko and Ciechanover 1998). Recent studies have demonstrated the relation between ubiquitin-mediated proteolysis, conidial germination and pathogenicity in M. oryzae (Oh et al 2012). In our study, the 26S proteasome nonATPase regulatory subunit 12 (spot 75) and proteasome A-type (spot 106) were identified in the conidial proteomes of both stages, but up-regulated in ungerminated conidia.…”

SUMOylation is required for fungal development and pathogenicity in the rice blast fungus Magnaporthe oryzae

“…Unlike ubiquitination, SUMOylation does not involve protein degradation, but instead enhances protein stability (Müller et al ., ). A previous study on ubiquitination in M. oryzae identified SUMO, E1 and E2 enzymes as ubiquitination components using a domain search method (Oh et al ., ). However, SUMOylation and other PTMs in yeast utilize different machineries (Johnson et al ., ; Müller et al ., ).…”

Autophagy-related protein MoAtg14 is involved in differentiation, development and pathogenicity in the rice blast fungus Magnaporthe oryzae

“…The whole infectious cycle of M. oryzae , from surface recognition, adherence, and appressorium formation to infectious growth and pathogenicity, is closely related to signal transduction pathways and protein degradation processes. The typical signal transduction pathways, including mitogen activated protein kinase (MAPK), cyclic adenosine monophosphate (cAMP), and calcium signal transduction pathways4567, and the protein degradation processes, including autophagy8910, ubiquitin mediated protein degradation111213 and calpains1415, have been confirmed to play significant roles in cell cycling, cellular differentiation and pathogenesis of M. oryzae .…”