10.3389/fpls.2018.00718.s003 Jianhua Xiang Jianhua Xiang Xiaoyun Zhou Xiaoyun Zhou Xianwen Zhang Xianwen Zhang Ailing Liu Ailing Liu Yanci Xiang Yanci Xiang Mingli Yan Mingli Yan Yan Peng Yan Peng Xinbo Chen Xinbo Chen Image_2_The Arabidopsis AtUNC-93 Acts as a Positive Regulator of Abiotic Stress Tolerance and Plant Growth via Modulation of ABA Signaling and K+ Homeostasis.TIF Frontiers 2018 Arabidopsis thaliana abiotic stress plant growth abscisic acid K+ homeostasis AtUNC-93 2018-05-30 11:17:02 Figure https://frontiersin.figshare.com/articles/figure/Image_2_The_Arabidopsis_AtUNC-93_Acts_as_a_Positive_Regulator_of_Abiotic_Stress_Tolerance_and_Plant_Growth_via_Modulation_of_ABA_Signaling_and_K_Homeostasis_TIF/6391556 <p>Potassium (K<sup>+</sup>) is one of the essential macronutrients required for plant growth and development, and the maintenance of cellular K<sup>+</sup> homeostasis is important for plants to adapt to abiotic stresses and growth. However, the mechanism involved has not been understood clearly. In this study, we demonstrated that AtUNC-93 plays a crucial role in this process under the control of abscisic acid (ABA). AtUNC-93 was localized to the plasma membrane and mainly expressed in the vascular tissues in Arabidopsis thaliana. The atunc-93 mutants showed typical K<sup>+</sup>-deficient symptoms under low-K<sup>+</sup> conditions. The K<sup>+</sup> contents of atunc-93 mutants were significantly reduced in shoots but not in roots under either low-K<sup>+</sup> or normal conditions compared with wild type plants, whereas the AtUNC-93-overexpressing lines still maintained relatively higher K<sup>+</sup> contents in shoots under low-K<sup>+</sup> conditions, suggesting that AtUNC-93 positively regulates K<sup>+</sup> translocation from roots to shoots. The atunc-93 plants exhibited dwarf phenotypes due to reduced cell expansion, while AtUNC-93-overexpressing plants had larger bodies because of increased cell expansion. After abiotic stress and ABA treatments, the atunc-93 mutants was more sensitive to salt, drought, osmotic, heat stress and ABA than wild type plants, while the AtUNC-93-overexpressing lines showed enhanced tolerance to these stresses and insensitive phenotype to ABA. Furthermore, alterations in the AtUNC-93 expression changed expression of many ABA-responsive and stress-related genes. Our findings reveal that AtUNC-93 functions as a positive regulator of abiotic stress tolerance and plant growth by maintaining K<sup>+</sup> homeostasis through ABA signaling pathway in Arabidopsis.</p>