The NSvc4 Protein of Rice Stripe Virus Suppresses Chloroplast-Mediated Defense by Interacting with NbPsbQ.

The chloroplast, a key organelle for plant immunity, is frequently targeted by viral proteins to suppress host defense. Here, we demonstrate that NSvc4, the movement protein of rice stripe virus (Tenuivirus oryzaclavatae; genus Tenuivirus), functions as a chloroplast-localized virulence effector. We show that NSvc4 enters chloroplasts and directly associates with NbPsbQ, a subunit of the oxygen-evolving complex (OEC) of Photosystem II. This interaction competitively disrupts the binding of NbPsbQ to its native partners NbPsbO and NbPsbP, thereby dampening the accumulation of chloroplast-derived reactive oxygen species (cROS) and attenuating pathogen-triggered immune signaling. Genetic knockout of NbPsbQ enhanced plant susceptibility to RSV, confirming its role as a positive regulator of antiviral defense. Our study uncovers a distinct strategy whereby a viral movement protein inhibits chloroplast-mediated immunity by targeting extrinsic subunits of the OEC. These findings expand the functional scope of viral movement proteins and highlight the OEC as a critical battleground in plant-virus interactions.