LRR receptor kinase involved in the regulation of root and shoot growth, and root nodule organogenesis (PubMed:12442170, PubMed:12442172). Involved in long distance nodulation signaling events (PubMed:12442170, PubMed:12442172). 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:12442170, PubMed:12442172). Acts from shoot to root to control AON (PubMed:12442170, PubMed:12442172). Involved in the regulation of root colonization by arbuscular mycorrhizal (AM) fungi (PubMed:12442170, PubMed:12442172). 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, stems and flowers. Increased number of root nodules when inoculated with Mesorhizobium loti (PubMed:12442170, PubMed:12442172). Inhibition of shoot and root growth (PubMed:12442170, PubMed:12442172). Increase in arbuscular mycorrhizal (AM) fungus colonization intensity in roots (enhanced mycorrhizal phenotype) when inoculated with AM fungi (PubMed:12442170, PubMed:12442172). Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.