Plasmopara viticola effector PvCRN20 represses the import of VvDEG5 into chloroplasts to suppress immunity in grapevine

• Chloroplasts play a crucial role in plant defense against pathogens, making them primary targets for pathogen effectors that suppress host immunity. This study characterizes the Plasmopara viticola CRN-like effector, PvCRN20, which interacts with DEG5 in the cytoplasm but not with its interacting protein, DEG8, which is located in the chloroplast.
• By transiently overexpressing in tobacco leaves, we show that PvCRN20 could inhibit INF1- and Bax-triggered cell death. Constitutive expression of PvCRN20 suppresses the accumulation of reactive oxygen species (ROS) and promotes pathogen colonization. PvCRN20 reduces DEG5 entry into chloroplasts, thereby disrupting DEG5 and DEG8 interactions in chloroplasts.
• Overexpression of VvDEG5 and VvDEG8 induces ROS accumulation and enhances grapevine resistance to P. viticola, whereas knockout of VvDEG8 represses ROS production and promotes P. viticola colonization. Consistently, ectopic expression of VvDEG5 and VvDEG8 in tobacco promotes chloroplast-derived ROS accumulation, whereas co-expression of PvCRN20 counteracted this promotion by VvDEG5. Therefore, DEG5 is essential for the virulence function of PvCRN20. Although PvCRN20 is located in both the nucleus and cytoplasm, only cytoplasmic PvCRN20 suppresses plant immunity and promotes pathogen infection.
• Our results reveal that PvCRN20 dampens plant defenses by repressing the chloroplast import of DEG5, thus reducing host ROS accumulation and facilitating pathogen colonization.