Physical and Functional Interaction of the Arabidopsis K⁺ Channel AKT2 and Phosphatase AtPP2CA

• Published in: The Plant cell 2002-05, Vol.14 (5), p.1133-1146
• Main Authors: Chérel, Isabelle, Michard, Erwan, Platet, Nadine, Mouline, Karine, Alcon, Carine, Sentenac, Hervé, Thibaud, Jean-Baptiste
• Format: Article
• Language: English
• Subjects: abscisic acid; Abscisic Acid - pharmacology; Animals; Arabidopsis; Arabidopsis - enzymology; Arabidopsis - genetics; Arabidopsis - physiology; Arabidopsis Proteins; Arabidopsis thaliana; Complementary DNA; COS Cells; DNA, Complementary; drug effects; electrophysiology; enzymology; gene expression; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Enzymologic - drug effects; Gene Expression Regulation, Plant; Gene Expression Regulation, Plant - drug effects; genes; Genetics; Guard cells; ion transport; Life Sciences; messenger RNA; metabolism; nucleotide sequences; Oocytes; Oocytes - physiology; pharmacology; Phloem; Phosphatases; phosphoprotein phosphatase; Phosphoprotein Phosphatases; Phosphoprotein Phosphatases - genetics; Phosphoprotein Phosphatases - metabolism; physiology; Plant cells; Plant Epidermis; Plant Epidermis - enzymology; Plant Epidermis - genetics; Plant Epidermis - physiology; plant proteins; Plant Proteins - genetics; Plant Proteins - metabolism; Plant Roots; Plant Roots - enzymology; Plant Roots - genetics; Plant Roots - physiology; Plant Shoots; Plant Shoots - enzymology; Plant Shoots - genetics; Plant Shoots - physiology; Plants; Plants genetics; plasma membrane; potassium; Potassium Channels; Potassium Channels - genetics; Potassium Channels - metabolism; Protein Binding; Protein Phosphatase 2; Protein Phosphatase 2C; Proteins; RNA, Messenger; RNA, Messenger - metabolism; roots; Saccharomyces cerevisiae Proteins; shoots; Signal Transduction; Two-Hybrid System Techniques; Vanadates; Xenopus laevis
• ISSN: 1040-4651; 1532-298X
• DOI: 10.1105/tpc.000943

The AKT2 K+ channel is endowed with unique functional properties, being the only weak inward rectifier characterized to date in Arabidopsis. The gene is expressed widely, mainly in the phloem but also at lower levels in leaf epiderm, mesophyll, and guard cells. The AKT2 mRNA level is upregulated by abscisic acid. By screening a two-hybrid cDNA library, we isolated a protein phosphatase 2C (AtPP2CA) involved in abscisic acid signaling as a putative partner of AKT2. We further confirmed the interaction by in vitro binding studies. The expression of AtPP2CA (β-glucuronidase reporter gene) displayed a pattern largely overlapping that of AKT2 and was upregulated by abscisic acid. Coexpression of AtPP2CA with AKT2 in COS cells and Xenopus laevis oocytes was found to induce both an inhibition of the AKT2 current and an increase of the channel inward rectification. Site-directed mutagenesis and pharmacological analysis revealed that this functional interaction involves AtPP2CA phosphatase activity. Regulation of AKT2 activity by AtPP2CA in planta could allow the control of K+ transport and membrane polarization during stress situations.