title: Nitric oxide negatively regulates AKT1-mediated potassium uptake through modulating vitamin B6 homeostasis in Arabidopsis.
abstract: Nitric oxide (NO), an active signaling molecule in plants, is involved in numerous physiological processes and adaptive responses to environmental stresses. Under high-salt conditions, plants accumulate NO quickly, and reorganize Na(+) and K(+) contents. However, the molecular connection between NO and ion homeostasis is largely unknown. Here, we report that NO lowers K(+) channel AKT1-mediated plant K(+) uptake by modulating vitamin B6 biosynthesis. In a screen for Arabidopsis NO-hypersensitive mutants, we isolated sno1 (sensitive to nitric oxide 1), which is allelic to the previously noted mutant sos4 (salt overly sensitive 4) that has impaired Na(+) and K(+) contents and overproduces pyridoxal 5'-phosphate (PLP), an active form of vitamin B6. We showed that NO increased PLP and decreased K(+) levels in plant. NO induced SNO1 gene expression and enzyme activity, indicating that NO-triggered PLP accumulation mainly occurs through SNO1-mediated vitamin B6 salvage biosynthetic pathway. Furthermore, we demonstrated that PLP significantly repressed the activity of K(+) channel AKT1 in the Xenopus oocyte system and Arabidopsis root protoplasts. Together, our results suggest that NO decreases K(+) absorption by promoting the synthesis of vitamin B6 PLP, which further represses the activity of K(+) channel AKT1 in Arabidopsis. These findings reveal a previously unidentified pivotal role of NO in modulating the homeostasis of vitamin B6 and potassium nutrition in plants, and shed light on the mechanism of NO in plant acclimation to environmental changes.
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, China;
authors.forename: Jinchan
authors.initials: J
authors.lastname: Xia
authors.affiliation: Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742; and yhe@cnu.edu.cn ddkong169@gmail.com.
authors.forename: Dongdong
authors.initials: D
authors.lastname: Kong
authors.affiliation: College of Life Science and Technology, Huazhong Agriculture University, Wuhan 430070, China.
authors.forename: Shaowu
authors.initials: S
authors.lastname: Xue
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, China;
authors.forename: Wang
authors.initials: W
authors.lastname: Tian
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, China;
authors.forename: Nan
authors.initials: N
authors.lastname: Li
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, China;
authors.forename: Fang
authors.initials: F
authors.lastname: Bao
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, China;
authors.forename: Yong
authors.initials: Y
authors.lastname: Hu
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, China;
authors.forename: Jing
authors.initials: J
authors.lastname: Du
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, China;
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, China;
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Pan
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, China;
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, China;
authors.forename: Xiaochen
authors.initials: X
authors.lastname: Zhang
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, China;
authors.forename: Guoqi
authors.initials: G
authors.lastname: Niu
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, China;
authors.forename: Xue
authors.initials: X
authors.lastname: Feng
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, China;
authors.forename: Legong
authors.initials: L
authors.lastname: Li
authors.affiliation: College of Life Sciences, Capital Normal University, Beijing 100048, China; yhe@cnu.edu.cn ddkong169@gmail.com.
authors.forename: Yikun
authors.initials: Y
authors.lastname: He
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins; D006706:Homeostasis / Q000502:physiology*; D017136:Ion Transport / Q000502:physiology; D009569:Nitric Oxide / Q000235:genetics / Q000378:metabolism; D009865:Oocytes; D018517:Plant Roots / Q000166:cytology / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels; D011523:Protoplasts / Q000166:cytology / Q000378:metabolism; D011732:Pyridoxal Phosphate / Q000235:genetics / Q000378:metabolism; D025101:Vitamin B 6 / Q000096:biosynthesis* / Q000235:genetics; D014982:Xenopus laevis
chemical_list: D029681:Arabidopsis Proteins; D015221:Potassium Channels; C074500:AKT1 protein, Arabidopsis; D009569:Nitric Oxide; D011732:Pyridoxal Phosphate; D025101:Vitamin B 6; D011188:Potassium
keywords: electrophysiological studies; genetic approach; potassium nutrition