LRR receptor kinase involved in the regulation of root and shoot growth, and root nodule organogenesis (PubMed:12411574). Involved in long distance nodulation signaling events (PubMed:12411574). Involved in the autoregulation of nodulation (AON), a long distance systemic signaling from root to shoot and back again, which allows legumes to limit the number of root nodules formed based on available nitrogen and previous rhizobial colonization (PubMed:12411574). Acts from shoot to root to control AON (PubMed:12411574). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Expressed in roots, leaves, vegetative shoot apex, and reproductive floral apex. Dramatic increase in root nodule number when inoculated with symbiotic rhizobia. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. Extended N-terminus.