An AAA+ ATPase–F-box module regulates potato late blight resistance by affecting SOBIR1 stability

Abstract

Fine-tuning immune receptor stability is essential for maintaining the balance between defense and growth in crops. Here, we identify an AAA+ ATPase–F-box regulatory module that negatively regulates potato immunity by promoting the degradation of the immune co-receptor StSOBIR1. The AAA+ ATPase StGCN4 functions as a negative regulator of potato immunity. Silencing of StGCN4 markedly enhanced resistance to Phytophthora infestans without affecting plant growth, while overexpression increased susceptibility. StGCN4 interacts with the PP2-type F-box protein StPFB1 and stabilizes it at the plasma membrane, which also negatively regulate immunity and together they facilitate proteasomal degradation of StSOBIR1, thereby dampening receptor-mediated defense signaling. Suppression of StGCN4 or StPFB1 enhances reactive oxygen species (ROS) production, salicylic acid accumulation, and expression of defense-related genes, resulting in strong resistance to P. infestans without growth penalty. These findings reveal a previously unrecognized AAA+ ATPase–F-box module that controls receptor homeostasis and identify StGCN4 as a promising molecular target for breeding high-yielding and late blight resistant potato cultivars.