The effector Pi09160 targets the transcription factor StRAP2.3 to suppress its mediated transcriptional regulatory activity

Phytophthora infestans, the causal agent of potato late blight, secretes effector proteins to suppress plant immunity, though the molecular mechanisms remain incompletely defined. This study aimed to characterize the virulence function of effector Pi09160, identify its host target, and elucidate its mode of action. Transient expression of Pi09160 in Nicotiana benthamiana significantly enhanced susceptibility to P. infestans and suppressed flg22-induced reactive oxygen species (ROS) burst. Protein interaction assays (yeast two-hybrid, co-immunoprecipitation) confirmed Pi09160 directly binds the ethylene-responsive transcription factor StRAP2.3. Overexpression of StRAP2.3 in potato reduced disease severity, while its silencing enhanced susceptibility. Transcriptomics revealed StRAP2.3 activates defense-related pathways, including plant-pathogen interaction, MAPK signaling, and phenylpropanoid biosynthesis. Crucially, Pi09160 impaired StRAP2.3 binding to GCC-box cis-elements in target gene promoters (StPR4) in vitro , suppressing transcriptional activation. These results demonstrate Pi09160 subverts immunity by hijacking a host transcription factor, revealing a novel effector mechanism with implications for engineered disease resistance.