The Arabidopsis Outward K+Channel GORK Is Involved in Regulation of Stomatal Movements and Plant Transpiration

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 100; no. 9; pp. 5549 - 5554
• Main Authors: Hosy, Eric, Vavasseur, Alain, Mouline, Karine, Dreyer, Ingo, Gaymard, Frédéric, Porée, Fabien, Boucherez, Jossia, Lebaudy, Anne, Bouchez, David, Véry, Anne-Aliénor, Simonneau, Thierry, Thibaud, Jean-Baptiste, Sentenac, Hervé
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 29-04-2003; National Acad Sciences; The National Academy of Sciences
• Subjects: Arabidopsis - metabolism; Arabidopsis - physiology; Biological Sciences; Cell membranes; Cellular Biology; Flowers & plants; Genetics; Guard cells; Life Sciences; Patch-Clamp Techniques; Peels; Plant epidermis; Plant reproduction; Plants; Potassium Channels - genetics; Potassium Channels - physiology; Protoplasts; Stomatal movement; Transpiration; Turgor pressure; Water - metabolism; Water loss; ABA; THALIANA
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0733970100

Microscopic pores present in the epidermis of plant aerial organs, called stomata, allow gas exchanges between the inner photosynthetic tissue and the atmosphere. Regulation of stomatal aperture, preventing excess transpirational vapor loss, relies on turgor changes of two highly differentiated epidermal cells surrounding the pore, the guard cells. Increased guard cell turgor due to increased solute accumulation results in stomatal opening, whereas decreased guard cell turgor due to decreased solute accumulation results in stomatal closing. Here we provide direct evidence, based on reverse genetics approaches, that the Arabidopsis GORK Shaker gene encodes the major voltage-gated outwardly rectifying K+channel of the guard cell membrane. Expression of GORK dominant negative mutant polypeptides in transgenic Arabidopsis was found to strongly reduce outwardly rectifying K+channel activity in the guard cell membrane, and disruption of the GORK gene (T-DNA insertion knockout mutant) fully suppressed this activity. Bioassays on epidermal peels revealed that disruption of GORK activity resulted in impaired stomatal closure in response to darkness or the stress hormone azobenzenearsonate. Transpiration measurements on excised rosettes and intact plants (grown in hydroponic conditions or submitted to water stress) revealed that absence of GORK activity resulted in increased water consumption. The whole set of data indicates that GORK is likely to play a crucial role in adaptation to drought in fluctuating environments.