The receptor-like cytoplasmic kinase PCRK1 contributes to pattern-triggered immunity against Pseudomonas syringae in Arabidopsis thaliana.

• In this paper we describe PATTERN-TRIGGERED IMMUNITY (PTI) COMPROMISED RECEPTOR-LIKE CYTOPLASMIC KINASE 1 (PCRK1) of Arabidopsis thaliana, an RLCK that is important for defense against the pathogen Pseudomonas syringae pv. maculicola ES4326 (Pma ES4326). • 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 PCRK1 during pathogen infection. • Expression of PCRK1 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 ES4326 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 PCRK1 in activation of early immune responses. A PCRK1 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 ES4326 growth phenotype. • Our study shows that PCRK1 plays an important role during PTI and that a conserved lysine residue in the putative kinase domain is important for PCRK1 function. [ABSTRACT FROM AUTHOR]