title: Osmotic stress responses and plant growth controlled by potassium transporters in Arabidopsis.
abstract: Osmotic adjustment plays a fundamental role in water stress responses and growth in plants; however, the molecular mechanisms governing this process are not fully understood. Here, we demonstrated that the KUP potassium transporter family plays important roles in this process, under the control of abscisic acid (ABA) and auxin. We generated Arabidopsis thaliana multiple mutants for K(+) uptake transporter 6 (KUP6), KUP8, KUP2/SHORT HYPOCOTYL3, and an ABA-responsive potassium efflux channel, guard cell outward rectifying K(+) channel (GORK). The triple mutants, kup268 and kup68 gork, exhibited enhanced cell expansion, suggesting that these KUPs negatively regulate turgor-dependent growth. Potassium uptake experiments using (86)radioactive rubidium ion ((86)Rb(+)) in the mutants indicated that these KUPs might be involved in potassium efflux in Arabidopsis roots. The mutants showed increased auxin responses and decreased sensitivity to an auxin inhibitor (1-N-naphthylphthalamic acid) and ABA in lateral root growth. During water deficit stress, kup68 gork impaired ABA-mediated stomatal closing, and kup268 and kup68 gork decreased survival of drought stress. The protein kinase SNF1-related protein kinases 2E (SRK2E), a key component of ABA signaling, interacted with and phosphorylated KUP6, suggesting that KUP functions are regulated directly via an ABA signaling complex. We propose that the KUP6 subfamily transporters act as key factors in osmotic adjustment by balancing potassium homeostasis in cell growth and drought stress responses.
authors: Laboratory of Plant Molecular Physiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
authors: Yuriko
authors: Y
authors: Osakabe
authors: Naoko
authors: N
authors: Arinaga
authors: Taishi
authors: T
authors: Umezawa
authors: Shogo
authors: S
authors: Katsura
authors: Keita
authors: K
authors: Nagamachi
authors: Hidenori
authors: H
authors: Tanaka
authors: Haruka
authors: H
authors: Ohiraki
authors: Kohji
authors: K
authors: Yamada
authors: So-Uk
authors: SU
authors: Seo
authors: Mitsuru
authors: M
authors: Abo
authors: Etsuro
authors: E
authors: Yoshimura
authors: Kazuo
authors: K
authors: Shinozaki
authors: Kazuko
authors: K
authors: Yamaguchi-Shinozaki
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism; D017360:Arabidopsis / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000235:genetics; D003681:Dehydration; D055864:Droughts; D007210:Indoleacetic Acids / Q000378:metabolism; D009154:Mutation; D009995:Osmosis; D010766:Phosphorylation; D018517:Plant Roots / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D054046:Plant Stomata / Q000235:genetics / Q000502:physiology; D030821:Plants, Genetically Modified; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism; D013312:Stress, Physiological
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D015221:Potassium Channels; D000040:Abscisic Acid; D011494:Protein Kinases; C472139:OST1 protein, Arabidopsis; D011188:Potassium
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