Characterization of plant phenotypes associated with loss-of-function of AtCNGC1, a plant cyclic nucleotide gated cation channel.

Of the 57 cation channel genes in the Arabidopsis genome, over a third encode cyclic nucleotide gated cation channels (CNGCs). CNGCs are ion channels regulated by cytosolic signaling molecules (cyclic nucleotides, calmodulin, and Ca(2+)), and which conduct Ca(2+) as well as K(+) and in some cases Na(+). Little is currently known about the role CNGCs may play in plant growth and development. Here, we examined the hypothesis that an Arabidopsis thaliana genotype containing a null mutation in one of the CGNC genes (AtCNGC1) would display cation uptake-related growth phenotype differences from wild type (WT) plants. We determined that AtCNGC1 protein is primarily expressed in the roots of Arabidopsis seedlings. Seedlings lacking this protein had slightly (6-22%) lower shoot Ca(2+) than WT plants. Primary roots of Atcngc1 mutant seedlings grew faster than roots of WT plants, and had larger angles of gravicurvature and less nitric oxide generation upon gravistimulation. We conclude that channels formed (at least in part) by AtCNGC1 contribute (along with other channels) to Ca(2+) uptake into plants, and that Ca(2+) uptake into roots through AtCNGC1 affects some aspects of growth in the primary root of Arabidopsis seedlings.