Peg Periphery-localized Effector Ppe: Unraveling Magnaporthe oryzae Invasion Strategies

Plant-pathogen interactions are governed by the ability of phytopathogens to utilize specialized infection structures and effectors for successful invasion. The rice blast disease, caused by the fungus Magnaporthe oryzae, poses a significant threat to global food production. In this study, we investigate the role of a novel apoplastic effector, peg periphery-localized effector (Ppe), in M. oryzae invasion. We demonstrate that Ppe is specifically expressed during plant infection and exhibits dynamic spatiotemporal localizations. It is preferentially localized to a ring structure at the collar of penetration peg formed by appressoria or transpressoria although occasionally observed in vesicle-like structures within the biotrophic interfacial complex (BIC). Through the unconventional secretion pathway involving the exocyst complex and t-SNAREs, Ppe is delivered to the rice apoplastic interface. Genetic analysis reveals that while the Δppe mutant does not exhibit developmental differences compared to the wild type, it displays reduced pathogenicity due to defects in rice penetration and expansion. Furthermore, Ppe suppresses the expression of plant defense-related genes and attenuates callose deposition at plasmodesmata, thereby facilitating fungal invasion. Our findings highlight the key role of Ppe as a novel effector in M. oryzae invasion and emphasize the significance of the peg as an infection structure and effector deployment site for overcoming host defense responses.