Screening and Validation of Interacting Proteins of Receptor-like Cytoplasmic Kinase OsRLCK118 Involved in Rice Blast Resistance

Rice blast, caused by <i>Magnaporthe oryzae</i>, severely threatens global rice production. Although the receptor-like cytoplasmic kinase OsRLCK118 positively regulates rice immunity, its downstream signaling mechanism remains unknown. To systematically identify OsRLCK118-interacting proteins, we performed immunoprecipitation-mass spectrometry (IP-MS) and a yeast library screen, yielding 781 and 287 candidates, respectively, with 35 overlapping hits. Among these, OsSAMS1, a known positive regulator of blast resistance, was selected for validation. Membrane yeast two-hybrid, split-luciferase complementation, and co-immunoprecipitation assays confirmed the physical interaction between OsRLCK118 and OsSAMS1. Furthermore, in vitro kinase assays showed that OsRLCK118 specifically phosphorylates OsSAMS1. These results uncover a novel signaling axis connecting pathogen recognition to ethylene biosynthesis via OsRLCK118-dependent phosphorylation of OsSAMS1, providing both mechanistic insight into rice immunity and potential genetic targets for resistance breeding.