Tyrosine phosphorylation of the lectin receptor‐like kinase LORE regulates plant immunity

Plant pattern recognition receptors (PRRs) perceive pathogen‐associated molecular patterns (PAMPs) to activate immune responses. Medium‐chain 3‐hydroxy fatty acids (mc‐3‐OH‐FAs), which are widely present in Gram‐negative bacteria, were recently shown to be novel PAMPs in Arabidopsis thaliana . The Arabidopsis PRR LIPOOLIGOSACCHARIDE‐SPECIFIC REDUCED ELICITATION (LORE) is a G‐type lectin receptor‐like kinase that recognizes mc‐3‐OH‐FAs and subsequently mounts an immune response; however, the mechanisms underlying LORE activation and downstream signaling are unexplored. Here, we report that one of the mc‐3‐OH‐FAs, 3‐OH‐C10:0, induces phosphorylation of LORE at tyrosine residue 600 (Y600). Phosphorylated LORE subsequently trans‐phosphorylates the receptor‐like cytoplasmic kinase PBL34 and its close paralogs, PBL35 and PBL36, and therefore activates plant immunity. Phosphorylation of LORE Y600 is required for downstream phosphorylation of PBL34, PBL35, and PBL36. However, the Pseudomonas syringae effector HopAO1 targets LORE, dephosphorylating the tyrosine‐phosphorylated Y600 and therefore suppressing the immune response. These observations uncover the mechanism by which LORE mediates signaling in response to 3‐OH‐C10:0 in Arabidopsis . Synopsis The Arabidopsis lectin receptor‐like kinase LORE serves as pattern‐recognition receptor for bacterial fatty acid metabolites. Here, LORE‐mediated activation of plant immune responses is shown to be mediated by LORE auto‐phosphorylation and activation of novel receptor‐like cytoplasmic kinases. LORE exhibits tyrosine kinase activity. Bacterial fatty acid metabolite 3‐OH‐C10:0 activates LORE via its phosphorylation on Tyr600. LORE phosphorylates receptor‐like cytoplasmic kinases PBL34/PBL35/PBL36 to activate immune responses. Bacterial pathogen P. syringae inhibits LORE via the secreted tyrosine phosphatase HopAO1. Graphical Abstract A bacterial fatty acid metabolite induces immune response in Arabidopsis via receptor‐like cytoplasmic kinases PBL34/PBL35/PBL36 downstream of the receptor kinase LORE.