Acts as cyclic nucleotide-gated ion channel. Permeable to potassium and sodium in a cyclic nucleotide-dependent fashion (cAMP or cGMP). Might constitute a common downstream component of the signaling pathways leading to hypersensitive response (HR). Homotetramer or heterotetramer. Induced by both ethylene and methyl jasmonate treatments, or after pathogen attack. The binding of calmodulin to the C-terminus might interfere with cyclic nucleotide binding and thus channel activation. Loss-of-function mutation results in the loss of the hypersensitive response leading to broad spectrum disease resistance, and displays a lesion-mimic phenotype. Belongs to the cyclic nucleotide-gated cation channel (TC 1.A.1.5) family.