Journal Article

Osmotic Stress Responses and Plant Growth Controlled by Potassium Transporters in Arabidopsis

Osakabe, Yuriko, Yoshimura, Etsuro, Yamaguchi-Shinozaki, Kazuko, Nagamachi, Keita, Shinozaki, Kazuo, Tanaka, Hidenori, Seo, So-Uk, Yamada, Kohji, Abo, Mitsuru, Arinaga, Naoko, Katsura, Shogo, Ohiraki, Haruka, Umezawa, Taishi

2013

Overview

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 ⁸⁶radioactive rubidium ion (⁸⁶Rb⁺) 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 ABAmediated 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.

• Publisher: American Society of Plant Biologists
• Subject: abscisic acid / Abscisic Acid - metabolism / Arabidopsis / Arabidopsis - physiology / Arabidopsis Proteins - genetics / Arabidopsis Proteins - metabolism / Auxins / Biological Transport - genetics / cell growth / Dehydration / Drought / Droughts / Gene expression regulation / Guard cells / homeostasis / Indoleacetic Acids - metabolism / Mutation / Osmosis / osmotic stress / Phosphorylation / Plant cells / plant growth / plant response / Plant roots / Plant Roots - cytology / Plant Roots - genetics / Plant Roots - metabolism / Plant Stomata - genetics / Plant Stomata - physiology / Plants / Plants, Genetically Modified / Potassium / Potassium - metabolism / Potassium Channels - genetics / Potassium Channels - metabolism / Protein Kinases - metabolism / stress response / Stress, Physiological / Transgenic plants / transporters / water stress