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Plant Cell Advance Online Publication
Published on May 2, 2002; 10.1105/tpc.000943

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Received December 7, 2001
Accepted February 18, 2002

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

Isabelle Chérel 1*, Erwan Michard 1, Nadine Platet 1, Karine Mouline 1, Carine Alcon 1, Hervé Sentenac 1, and Jean-Baptiste Thibaud 1

1 Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, Unité Mixte de Recherche 5004 Agro-M/Centre National de la Recherche Scientifique/Institut National de la Recherche Agronomique/Université Montpellier II, Place Viala, 34060 Montpellier Cedex 1, France

* To whom correspondence should be addressed. E-mail: cherel{at}ensam.inra.fr.

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 (ß-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.






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