Involved in the activation of early immune responses. Plays a role in pattern-triggered immunity (PTI) induced by pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) (PubMed:25711411). Contributes to PTI in response to the bacterial pathogen Pseudomonas syringae pv maculicola strain ES4326 (PubMed:25711411, PubMed:26237268). Contributes to PTI in response to the bacterial pathogen Pseudomonas syringae pv tomato strain DC3000 (PubMed:25711411). Functions redundantly with PCRK2 in basal resistance against bacterial pathogens and in regulation of plant immunity. Functions together with PCRK2 downstream of the PAMP receptor FLS2. Contributes to the induction of SARD1 and CBP60G, which are transcriptional activator of ICS1, an enzyme involved in salicylate (SA) biosynthesis upon pathogen attack (PubMed:27208222). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with FLS2. Induced by infection with the bacterial pathogen Pseudomonas syringae pv maculicola strain ES4326, but not by microbe-associated molecular patterns (MAMPs) such as flg22. No visible phenotype under normal growth conditions, but mutant plants exhibit increased susceptibility to infection with the bacterial pathogens Pseudomonas syringae pv maculicola strain ES4326 and pv tomato strain DC3000. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.