Minisymposium 13: Membrane Transport

Add this abstract to my Itinerary

Abs # M1303: Plasma membrane localization, genetic complementation and function of CNGC10, a calmodulin-binding potassium channel of Arabidopsis.

Presenter:	Christopher, David A       Contact Presenter
Authors	Christopher, David A (A)   Borsics, Tamas  (A)   Onzighi-Assoume, Christy  (B)   Penner, Reinhold  (A)   Staehelin, L. Andrew  (B)
Affiliations:	(A): University of Hawaii (B): University of Colorado

We have isolated and characterized AtCNGC10, one of the 20 members of the family of cyclic nucleotide (CN)-gated and calmodulin (CaM)-regulated channels (CNGCs) from Arabidopsis thaliana. AtCNGC10 binds CaM in a C-terminal subregion that contains a basic amphiphillic structure characteristic of CaM-binding proteins and overlaps with the predicted CN-binding domain. Patch clamp analysis of AtCNGC10, when expressed in stably transfected human embryonic kidney cells (HEK293), measured significant K+ currents relative to cells with empty vector. An AtCNGC10-eGFP fusion was targeted to the HEK293 plasma membrane. In leaf and root cells, AtCNGC10 was localized to the plasma membrane, endoplasmic reticulum, golgi and membrane vesicles via immunoelectron microscopy. AtCNGC10 complemented K+ channel uptake mutants of Esherichia coli (LB650), yeast (Saccharomyces cerevisiae CY162) and Arabidopsis (akt1-1). Sense 35S-AtCNGC10 transformed into the Arabidopsis akt1-1 mutant, improved growth 1.7 fold on a potassium-limited medium relative to the vector control. Coexpression of CaM and AtCNGC10 in E. coli revealed Ca2+/CaM inhibited cell growth by 40%, while cGMP reversed the inhibition by Ca2+/CaM, in a AtCNGC10-dependent manner. Relative to wild type Columbia, antisense AtCNGC10 plants had 45% less potassium, flowered 11 days earlier, had a 25% reduction in leaf surface area, thickness and palisade parenchyma cell length, slower root gravitropism, and higher starch levels in chloroplasts. These studies demonstrated a role for the CaM-binding channel, AtCNGC10, in mediating the uptake of K+ across the plasma membrane in plants, which is essential for normal growth and development. This research was supported by the U.S. Dept. of Energy Biosciences Program (DE-FG03-97ER20273).