Lysin motif (LysM) receptor kinase required as a cell surface receptor for chitin elicitor (chitooligosaccharides) signaling leading to innate immunity in response to biotic stresses (By similarity). The CERK1, MEKK1a/b, MKK1a/b/c and MPK4a/b proteins are involved in pathogen defense. The pathway induces rapid growth inhibition, cell wall depositions and accumulation of defense-related transcripts. This protein is required for response to chitin. Is able to complement the A.thaliana cerk1 mutant (PubMed:27268428). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Up-regulated in response to chitosan. Chitin treatment does not lead to growth inhibition or reduced cell wall-associated depositions in contrast to the wild-type. No chitin-, chitosan- or chitin hexamer-induced MPK phosphorylation. Peptidyl glycan (PGN) from S.aureus does not induce MPK phosphorylation either. Reduced accumulation of PAL4 and CHS transcripts in response to chitin. Tissues fail to exhibit enhanced conductivity in an electrolyte leakage assay. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.