Involved in the perception of symbiotic fungi and bacteria. Part of the perception/transduction system leading to nodulation or mycorrhizal infection (PubMed:12087406, PubMed:12087405). Phosphorylates PUB1 (PubMed:26839127). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Binds to PUB1. Expressed constitutively in the entire root system, except in root meristems. Autophosphorylated. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus.