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.
In plants, numerous receptor-like kinases (RLKs) function as potential pattern recognition receptors (PRRs) involved in perceiving ligands to trigger pattern-triggered immunity (PTI); however, the roles of most RLKs remain uncharacterized. A previous study showed that the potato receptor-like kinase StLRPK1 interacts with the co-receptor SERK3A/BAK1 to positively regulate resistance against Phytophthora infestans, yet the underlying mechanism remains unknown. Here, we identified StLecRK. IX, a potato RLK that interacts with StLRPK1. The expression of StLecRK. IX was up-regulated in response to P. infestans inoculation. Transient overexpression of StLecRK. IX triggered strong cell death in Nicotiana benthamiana leaves. Moreover, stable overexpression of either StLecRK. IX or its N. benthamiana ortholog NbLecRK. IX significantly enhanced late blight resistance in both potato and N. benthamiana by activating a cascade of immune responses, including reactive oxygen species (ROS) burst, transcriptional upregulation of PTI marker genes, and callose deposition. StLecRK. IX contains two conserved functional motifs, HRD and DFG, within its kinase domain and exhibits strong kinase activity. Furthermore, we demonstrate that StLRPK1 and StLecRK. IX form a ternary protein complex with the co-receptor SERK3A/BAK1 to positively regulate late blight resistance. Together, these findings expand our understanding of plant RLK functions in late blight resistance and provide a strategic basis for utilizing StLecRK. IX and StLRPK1 to improve potato resistance, and highlight StLecRK. IX as a promising target for engineering disease resistance in crops.
Zhu Yang, Lang Liu, Chunju Yin et al.· Plant Science· 0 citations