The receptor‐like cytoplasmic kinase PCRK 1 contributes to pattern‐triggered immunity against Pseudomonas syringae in Arabidopsis thaliana

Summary In this paper we describe PATTERN ‐ TRIGGERED IMMUNITY ( PTI ) COMPROMISED RECEPTOR ‐ LIKE CYTOPLASMIC KINASE 1 ( PCRK 1 ) of Arabidopsis thaliana , an RLCK that is important for defense against the pathogen Pseudomonas syringae pv. maculicola ES 4326 ( Pma ES 4326). We examined defense responses such as bacterial growth, production of reactive oxygen species ( ROS ) and callose deposition in pcrk1 mutant plants to determine the role of PCRK 1 during pathogen infection. Expression of PCRK 1 was induced following pathogen infection. Pathogen growth was significantly higher in pcrk1 mutant lines than in wild‐type Col‐0. Mutant pcrk1 plants showed reduced pattern‐triggered immunity ( PTI ) against Pma ES 4326 after pretreatment with peptides derived from flagellin (flg22), elongation factor‐Tu (elf18), or an endogenous protein (pep1). Deposition of callose was reduced in pcrk1 plants, indicating a role of PCRK 1 in activation of early immune responses. A PCRK 1 transgene containing a mutation in a conserved lysine residue important for phosphorylation activity of kinases (K118E) failed to complement a pcrk1 mutant for the Pma ES 4326 growth phenotype. Our study shows that PCRK 1 plays an important role during PTI and that a conserved lysine residue in the putative kinase domain is important for PCRK 1 function.