Transcription activator that binds to the DNA consensus sequence 5'-[ACG]CGCG[GTC]-3'. Binds calmodulin in a calcium-dependent manner in vitro (PubMed:12218065). Regulates transcriptional activity in response to calcium signals (Probable). Involved in freezing tolerance in association with CAMTA1 and CAMTA2 (PubMed:23581962). Required for the cold-induced expression of DREB1B/CBF1, DREB1C/CBF2, ZAT12 and GOLS3 (PubMed:19270186). Involved in response to cold. Contributes together with CAMTA5 to the positive regulation of the cold-induced expression of DREB1A/CBF3, DREB1B/CBF1 and DREB1C/CBF2 (PubMed:28351986). Involved together with CAMTA2 and CAMTA4 in the positive regulation of a general stress response (GSR) (PubMed:25039701). Involved in the regulation of GSR amplitude downstream of MEKK1 (PubMed:25157030). Involved in the regulation of a set of genes involved in defense responses against pathogens (PubMed:18298954). Involved in the regulation of both basal resistance and systemic acquired resistance (SAR) (PubMed:21900483). Acts as negative regulator of plant immunity (PubMed:19122675, PubMed:21900483, PubMed:22345509, PubMed:28407487). Binds to the promoter of the defense-related gene EDS1 and represses its expression (PubMed:19122675). Binds to the promoter of the defense-related gene NDR1 and represses its expression (PubMed:22345509). Involved in defense against insects (PubMed:23072934, PubMed:22371088). Required for tolerance to the generalist herbivore Trichoplusia ni, and contributes to the positive regulation of genes associated with glucosinolate metabolism (PubMed:23072934). Required for tolerance to Bradysia impatiens larvae. Mediates herbivore-induced wound response (PubMed:22371088). Required for wound-induced jasmonate accumulation (PubMed:23072934, PubMed:22371088). Involved in the regulation of ethylene-induced senescence by binding to the promoter of the senescence-inducer gene EIN3 and repressing its expression (PubMed:22345509). Interacts with SR1IP1 (PubMed:24528504). Interacts with DSC1 (PubMed:28407487). Expressed in roots, stems, leaves, carpels, and siliques, but not in stigmas or other parts of the flower. By heat shock, UVB, salt, wounding, ethylene and methyl jasmonate (PubMed:11162426, PubMed:12218065). Induced by infection with the fungal pathogen Golovinomyces cichoracearum (powdery mildew) and the bacterial pathogen Pseudomonas syringae pv tomato strain DC3000 (PubMed:22345509). Ubiquinated during pathogen infection. Ubiquitination leads to its subsequent proteasome-dependent degradation, thus allowing the establishment of plant defense response. 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). No visible phenotype under normal growth conditions, but the double mutants camt2 and camt3 exhibit dwarf phenotypes (PubMed:23581962). Reduced growth, chlorosis, spontaneous lesions and constitutive expression of defense-related genes when grown under 22 degrees Celsius (PubMed:18298954, PubMed:19122675, PubMed:28407487). Enhanced sensitivity to insect herbivores (PubMed:23072934, PubMed:22371088). The camta3-3D activation tagging mutant plants exhibit compromised systemic acquired resistance (SAR) and enhanced susceptibility to virulent pathogens. Belongs to the CAMTA family.