StLecRK. IX and StLRPK1 form a complex with StBAK1 to positively regulate potato late blight resistance

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.