OsExo70B1 Positively Regulates Disease Resistance to Magnaporthe oryzae in Rice

The exocyst, an evolutionarily conserved octameric protein complex, mediates tethering of vesicles to the plasma membrane in the early stage of exocytosis. Arabidopsis Exo70, a subunit of the exocyst complex, has been found to be involved in plant immunity. Here, we characterize the function of OsExo70B1 in rice. OsExo70B1 mainly expresses in leaf and shoot and its expression is induced by pathogen-associated molecular patterns (PAMPs) and rice blast fungus Magnaporthe oryzae (M. oryzae). Knocking out OsExo70B1 results in significantly decreased resistance and defense responses to M. oryzae compared to the wild type, including more disease lesions and enhanced fungal growth, downregulated expression of pathogenesis-related (PR) genes, and decreased reactive oxygen species accumulation. In contrast, the exo70B1 mutant does not show any defects in growth and development. Furthermore, OsExo70B1 can interact with the receptor-like kinase OsCERK1, an essential component for chitin reception in rice. Taken together, our data demonstrate that OsExo70B1 functions as an important regulator in rice immunity.