Calcium- and calmodulin-dependent protein kinase required for arbuscular mycorrhizal (AM) symbiosis (PubMed:16673936, PubMed:17965173, PubMed:18852152). Involved in response to water deprivation stress. Required for abscisic acid-induced antioxidant defense and oxidative stress tolerance during dehydration stress (PubMed:22869603). Functions upstream of MPK1 in an abscisic acid signaling pathway that regulates the activities of antioxidant enzymes and the production of hydrogen peroxide (PubMed:23777258). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Mainly expressed in roots and panicles. Detected in leaves, shoots and culms. Not induced by mycorrhization (PubMed:17965173). Induced by hydrogen peroxide, abscisic acid (ABA) and dehydration (PubMed:22869603). Autophosphorylation. Can restore mycorrhizal and rhizobial symbiosis and induces spontaneous nodulation in a Ljccamk mutant of Lotus japonicus. Can restore nodulation and mycorrhizal symbiosis to a Medicago truncatula dmi3 mutant. Belongs to the protein kinase superfamily. CAMK Ser/Thr protein kinase family. CaMK subfamily.