May play a role in signal transduction pathways that involve calcium as a second messenger (By similarity). May function in signal transduction pathways that positively regulate responses to cold, salt and drought stresses (PubMed:10929125). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Activated by calcium. Autophosphorylation may play an important role in the regulation of the kinase activity. Expressed in vascular tissues of crowns and roots, vascular bundles and central cylinder (PubMed:11726707). Expressed in roots, leaf blades, spikelets and developing seeds (PubMed:21136139). By cold and salt stresses (PubMed:10929125). Induced by N-acetylchitooligosaccharide elicitor (PubMed:12956525). Induced by UV-C (PubMed:24035516). There are 3 contiguous domains conserved in the CDPK subfamily: a kinase domain, an autoinhibitory (junction) domain and a calmodulin-like domain. The autoinhibitory domain (352-382) inactivates kinase activity under calcium-free conditions. Plants over-expressing CPK13 display enhanced tolerance to cold, drought and salt stresses. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. CDPK subfamily.