Plants resist pathogen invasion by triggering reactive oxygen species (ROS) burst. However, the molecular mechanism by which pathogens suppress ROS accumulation for successful infection remains to be elucidated. To address this concern, an effector protein Pst9653 from Puccinia striiformis f. sp. tritici (Pst), the causal agent of wheat stripe rust, was characterized. The function of Pst9653 during Pst infection was identified by RNA interference and overexpression in wheat. The interaction targets of Pst9653 were screened by yeast two-hybrid assays and further regulatory mode was also determined. The results showed that Pst9653, encoding a virulence effector, was significantly upregulated during Pst infection. Silencing of Pst9653 led to increased wheat resistance to stripe rust and restricted fungal development, whereas overexpressing Pst9653 greatly promoted Pst susceptibility in wheat. In addition, Pst9653 was shown to interact with wheat catalases TaCAT1 and TaCAT3. TaCAT3 was induced by Pst and negatively regulated wheat resistance to stripe rust. Co-expression of TaCAT3 and Pst9653 facilitates cytoplasmic enrichment of TaCAT3 in plants. Our findings reveal that Pst9653 is secreted and disrupts TaCAT3 import into peroxisomes to promote susceptibility-involved ROS scavenging in wheat. This study uncovers a novel regulation strategy to cope with excessive ROS accumulation under stress conditions.
