Cyclic nucleotide-gated ion channel required for directional pollen tube growth into the transmitting tract (PubMed:17726111, PubMed:26929345). Acts as a Ca(2+)-permeable divalent cation-selective channel inhibited by either lanthanum or gadolinium (PubMed:24380879). Regulated by CPK32 to mediate Ca(2+) transport across the plasma membrane in response to Ca(2+) oscillation (PubMed:24121288). Homomultimer (PubMed:24380879). Interacts with CPK32 (PubMed:24121288). focused at the cell perimeter of the growing pollen tube tip. Expressed in pollen grains. Not detected in leaves, roots or root hairs. The transmembrane domains are indispensable for pollen tube guidance. The binding of calmodulin to the C-terminus might interfere with cyclic nucleotide binding and thus channel activation. Male sterility. Belongs to the cyclic nucleotide-gated cation channel (TC 1.A.1.5) family.