Acts as cyclic nucleotide-gated ion channel. Permeable to potassium and calcium in a cyclic nucleotide-dependent fashion (cAMP or cGMP). Could also transport lithium, cesium and rubium and displays a strong selectivity against sodium. Seems to directly participate in pathogen-induced calcium influx. May function in homeostasis, re-establishing ionic balance after defense action and/or other stimuli. Could mediate the initiation of the developmentally regulated cell death programs. Homotetramer or heterotetramer (Potential). Binds calmodulin-1/4 with a higher affinity than calmodulin-2/3/5. A number of isoforms are produced. According to EST sequences. Expressed in the whole plant but only weakly in roots. Strongly expressed in the expanded cotyledons of 14-day-old seedlings and detected later in leaves after the transition to flowering. Also detected in flowers during organ senescence and in the dehiscence zone of siliques. Up-regulated by light. Transiently induced during leaf and culture senescence. The binding of calmodulin to the C-terminus might interfere with cyclic nucleotide binding and thus channel activation. Loss-of-function mutations cngc2-1 (dnd1-1) or cncg2-2 results in the loss of the hypersensitive response and leads to a broad spectrum disease resistance. These mutations lead to a specific and dramatic calcium hypersensitivity that results in severe reductions in plant size and seed yield. Belongs to the cyclic nucleotide-gated cation channel (TC 1.A.1.5) family.