Effector‐Mediated Spatial Reprogramming of Glycolate Oxidase Subverts Peroxisomal and Membrane‐Associated <scp>ROS</scp> Defences

Oomycete pathogens secrete hundreds of RXLR effectors into plant cells to modulate host immunity by targeting diverse plant proteins. Here, we report that the Peronophythora litchii RXLR effector PlAvh133 acts as a virulence factor and targets the litchi glycolate oxidase (GLO) LcGLO1, a key enzyme in photorespiration, thereby suppressing plant immunity. PlAvh133 localises to the plasma membrane (PM) in planta, and its first α-helix is vital for both its LcGLO1-binding activity and proper PM localisation. LcGLO1 is mainly confined to the peroxisomes, and its overexpression significantly enhanced resistance to downy blight in litchi. Conversely, silencing the Nicotiana benthamiana homologue of LcGLO1 increases plant susceptibility to the oomycete pathogen. Critically, PlAvh133 causes the relocation of LcGLO1 from peroxisomes to the PM and inhibits its enzymatic activity, leading to increased plant susceptibility. PM-localised LcGLO1 cooperates with catalase (CAT) LcCATB to suppress reactive oxygen species (ROS) burst. Meanwhile, PM-localised LcGLO1 destabilises respiratory burst oxidase homologue (RBOH) LcRBOHD by interacting with calcium-dependent protein kinase (CPK) LcCPK5, further reducing ROS production. Taken together, our findings unveil an unprecedented virulence mechanism by which a pathogen effector relocalises and inhibits host GLO1 activity, thereby simultaneously diminishing ROS production from both the peroxisomes and PM-localised RBOHD.