title: AtKC1 and CIPK23 Synergistically Modulate AKT1-Mediated Low-Potassium Stress Responses in Arabidopsis.
abstract: In Arabidopsis (Arabidopsis thaliana), the Shaker K(+) channel AKT1 conducts K(+) uptake in root cells, and its activity is regulated by CBL1/9-CIPK23 complexes as well as by the AtKC1 channel subunit. CIPK23 and AtKC1 are both involved in the AKT1-mediated low-K(+) (LK) response; however, the relationship between them remains unclear. In this study, we screened suppressors of low-K(+) sensitive [lks1 (cipk23)] and isolated the suppressor of lks1 (sls1) mutant, which suppressed the leaf chlorosis phenotype of lks1 under LK conditions. Map-based cloning revealed a point mutation in AtKC1 of sls1 that led to an amino acid substitution (G322D) in the S6 region of AtKC1. The G322D substitution generated a gain-of-function mutation, AtKC1(D), that enhanced K(+) uptake capacity and LK tolerance in Arabidopsis. Structural prediction suggested that glycine-322 is highly conserved in K(+) channels and may function as the gating hinge of plant Shaker K(+) channels. Electrophysiological analyses revealed that, compared with wild-type AtKC1, AtKC1(D) showed enhanced inhibition of AKT1 activity and strongly reduced K(+) leakage through AKT1 under LK conditions. In addition, phenotype analysis revealed distinct phenotypes of lks1 and atkc1 mutants in different LK assays, but the lks1 atkc1 double mutant always showed a LK-sensitive phenotype similar to that of akt1 This study revealed a link between CIPK-mediated activation and AtKC1-mediated modification in AKT1 regulation. CIPK23 and AtKC1 exhibit distinct effects; however, they act synergistically and balance K(+) uptake/leakage to modulate AKT1-mediated LK responses in Arabidopsis.
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, National Plant Gene Research Centre (X.-P.W., L.-M.C., W.-X.L., L.-K.S., F.-L.W., W.-H.W., Y.W.), and State Key Laboratory of Agrobiotechnology (Y.Z., Z.Z.), College of Biological Sciences, China Agricultural University, Beijing 100193, China.
authors.forename: Xue-Ping
authors.identifier: 0000-0002-3010-5685
authors.initials: XP
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, National Plant Gene Research Centre (X.-P.W., L.-M.C., W.-X.L., L.-K.S., F.-L.W., W.-H.W., Y.W.), and State Key Laboratory of Agrobiotechnology (Y.Z., Z.Z.), College of Biological Sciences, China Agricultural University, Beijing 100193, China.
authors.forename: Li-Mei
authors.initials: LM
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, National Plant Gene Research Centre (X.-P.W., L.-M.C., W.-X.L., L.-K.S., F.-L.W., W.-H.W., Y.W.), and State Key Laboratory of Agrobiotechnology (Y.Z., Z.Z.), College of Biological Sciences, China Agricultural University, Beijing 100193, China.
authors.forename: Wen-Xin
authors.initials: WX
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, National Plant Gene Research Centre (X.-P.W., L.-M.C., W.-X.L., L.-K.S., F.-L.W., W.-H.W., Y.W.), and State Key Laboratory of Agrobiotechnology (Y.Z., Z.Z.), College of Biological Sciences, China Agricultural University, Beijing 100193, China.
authors.forename: Li-Ke
authors.initials: LK
authors.lastname: Shen
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, National Plant Gene Research Centre (X.-P.W., L.-M.C., W.-X.L., L.-K.S., F.-L.W., W.-H.W., Y.W.), and State Key Laboratory of Agrobiotechnology (Y.Z., Z.Z.), College of Biological Sciences, China Agricultural University, Beijing 100193, China.
authors.forename: Feng-Liu
authors.initials: FL
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, National Plant Gene Research Centre (X.-P.W., L.-M.C., W.-X.L., L.-K.S., F.-L.W., W.-H.W., Y.W.), and State Key Laboratory of Agrobiotechnology (Y.Z., Z.Z.), College of Biological Sciences, China Agricultural University, Beijing 100193, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, National Plant Gene Research Centre (X.-P.W., L.-M.C., W.-X.L., L.-K.S., F.-L.W., W.-H.W., Y.W.), and State Key Laboratory of Agrobiotechnology (Y.Z., Z.Z.), College of Biological Sciences, China Agricultural University, Beijing 100193, China.
authors.forename: Ziding
authors.identifier: 0000-0002-9296-571X
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, National Plant Gene Research Centre (X.-P.W., L.-M.C., W.-X.L., L.-K.S., F.-L.W., W.-H.W., Y.W.), and State Key Laboratory of Agrobiotechnology (Y.Z., Z.Z.), College of Biological Sciences, China Agricultural University, Beijing 100193, China.
authors.forename: Wei-Hua
authors.identifier: 0000-0002-0642-5523
authors.initials: WH
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, National Plant Gene Research Centre (X.-P.W., L.-M.C., W.-X.L., L.-K.S., F.-L.W., W.-H.W., Y.W.), and State Key Laboratory of Agrobiotechnology (Y.Z., Z.Z.), College of Biological Sciences, China Agricultural University, Beijing 100193, China yiwang@cau.edu.cn.
authors.forename: Yi
authors.identifier: 0000-0002-3660-5859
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D005020:Ethyl Methanesulfonate; D005816:Genetic Complementation Test; D018525:Germination / Q000187:drug effects; D016296:Mutagenesis; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D018520:Plant Shoots / Q000187:drug effects / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology*; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D016415:Sequence Alignment; D051637:Shaker Superfamily of Potassium Channels / Q000378:metabolism*; D013312:Stress, Physiological / Q000187:drug effects*
chemical_list: D029681:Arabidopsis Proteins; C501895:LKT1 protein, Arabidopsis; D015221:Potassium Channels; D051637:Shaker Superfamily of Potassium Channels; C074500:AKT1 protein, Arabidopsis; D005020:Ethyl Methanesulfonate; C514581:CIPK23 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases; D011188:Potassium
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