Poster: Membrane transport
Abs #
164: Characterization of ion transport-related phenotypes of Arabidopsis plants with mutations in genes encoding cyclic nucleotide gated nonselective cation channels
Arabidopsis cyclic nucleotide gated cation channels (AtCNGCs) mediate cation transport across cell membranes. Cloned AtCNGCs conduct K, Na, and/or Ca in heterologous expression systems. Here, we identify the role ion transport by some of these channels has on plant growth. AtCNGC1 is expressed in roots, and conducts Na. AtCNGC1 deletion mutation plants (Atcngc1) have lower leaf Na. In addition, Atcngc1 seeds germinate better, and seedlings grow better than wild type (WT) on media with increasing Na. Na uptake into plants is reduced (by an unknown mechanism) when soil solution [Ca] is increased. AtCNGC conductance of monovalent cations is blocked by external Ca. We find that when growth medium Ca is increased, leaf Na is reduced in both WT and Atcngc1 plants, and Na levels in Atcngc1 plants are not lower that those of WT plants. Thus, we conclude that native CNGC channel complexes that contain AtCNGC1 contribute to Na uptake into plants. AtCNGC2 (known to conduct Ca) is strongly expressed in leaves. Growth of Atcngc2 mutant plants is hypersensitive to Ca. We associate this phenotype with reduced Ca uptake into leaves of Atcngc2 plants. We find lower Ca levels in leaves of Atcngc2 than WT plants on standard medium. In the presence of high growth medium Ca, leaf [Ca] increases in both WT and Atcngc2 plants, but less so in the mutants. We speculate that AtCNGC2, as a leaf cell inward Ca channel, facilitates Ca movement to the leaf from the root. In the absence of this channel, Ca may accumulate in roots to toxic levels. Functional genomics of the AtCNGCs is also being undertaken to investigate ionomic changes in all viable CNGC deletion mutants to help characterize the biological role of these channels. Supported by NSF awards MCB0344141 and DBI0077378.
