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MoRic8 Is a Novel Component of G-Protein Signaling During Plant Infection by the Rice Blast Fungus Magnaporthe oryzae

¹State Key Laboratory for Rice Biology, Biotechnology Institute, Zhejiang University, Huajiachi Campus, Hangzhou, 310029, People's Republic of China; ²School of Biosciences, University of Exeter, Geoffrey Pope Building, Exeter EX4 4QD, U.K.; ³Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Ministry of Agriculture, Zhejiang University, People's Republic of China

An insertional mutagenesis screen was used to investigate the biology of plant infection by the devastating rice blast pathogen, Magnaporthe oryzae. Here, we report the identification of a new mutant, LY-130, which is defective in multiple steps during infection-related morphogenesis and pathogenicity. Analysis of the mutation confirmed an insertion into gene MoRIC8, which encodes a 480-amino-acid protein that is a putative homologue of the Ric8 regulator of GTP-binding protein (G-protein) signaling, previously described in animals. Targeted gene deletion mutants of MoRIC8 were nonpathogenic and impaired in cellular differentiation associated with sporulation, sexual development, and plant infection. MoRic8 physically interacts with the Gα subunit MagB in yeast two-hybrid assays and appears to act upstream of the cyclic AMP response pathway that is necessary for appressorium morphogenesis. Taken together, our results indicate that MoRic8 may act as a novel regulator of the G-protein signaling during infection-related development of rice blast fungus M. oryzae.