Transcription activator that binds calmodulin in a calcium-dependent manner in vitro (PubMed:11925432). Binds to the DNA consensus sequence 5'-[ACG]CGCG[GTC]-3' (By similarity). Regulates transcriptional activity in response to calcium signals (Probable). Involved in freezing tolerance (PubMed:19270186). Involved in freezing tolerance in association with CAMTA2 and CAMTA3. Contributes together with CAMTA2 and CAMTA3 to the positive regulation of the cold-induced expression of DREB1A/CBF3, DREB1B/CBF1 and DREB1C/CBF2 (PubMed:23581962). Involved in drought stress responses by regulating several drought-responsive genes (PubMed:23547968). Involved in auxin signaling and responses to abiotic stresses (PubMed:20383645). Activates the expression of the V-PPase proton pump AVP1 in pollen (PubMed:14581622). Expressed in roots, stems, leaves, pollen and siliques. During leaf developlement, expressed in young leaf primordia, hydathodes of young leaf tips, hydathodes of the lobes in maturating leaves and lamina within the minor veins in adult leaves. During flower development, expressed in developing stamens, germinating pollen grains, ovules and developing seeds. Induced by UVB, wounding, ethylene and methyl jasmonate (PubMed:12218065). Induced by salt stress and heat shock (PubMed:12218065, PubMed:20383645). Induced by aluminum (PubMed:25627216). The two IQ domains are probably not interacting with calcium/calmodulin. No visible phenotype under normal growth conditions, but mutant seedling are hyper-responsive to auxin in hypocotyl growth inhibition (PubMed:20383645). No visible phenotype under normal growth conditions, but mutant seedling exhibit reduced drought tolerance (PubMed:23547968). No visible phenotype under normal growth conditions, but the double mutants camta1 and camta3 are impaired in freezing tolerance (PubMed:19270186). No visible phenotype under normal growth conditions, but the double mutants camt1 and camt3 exhibit semi-dwarf phenotypes (PubMed:19270186, PubMed:23581962). Belongs to the CAMTA family.