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Monder H, Maillard M, Chérel I, Zimmermann SD, Paris N, Cuéllar T, Gaillard I. Adjustment of K + Fluxes and Grapevine Defense in the Face of Climate Change. Int J Mol Sci 2021; 22:10398. [PMID: 34638737 PMCID: PMC8508874 DOI: 10.3390/ijms221910398] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 09/18/2021] [Accepted: 09/20/2021] [Indexed: 12/18/2022] Open
Abstract
Grapevine is one of the most economically important fruit crops due to the high value of its fruit and its importance in winemaking. The current decrease in grape berry quality and production can be seen as the consequence of various abiotic constraints imposed by climate changes. Specifically, produced wines have become too sweet, with a stronger impression of alcohol and fewer aromatic qualities. Potassium is known to play a major role in grapevine growth, as well as grape composition and wine quality. Importantly, potassium ions (K+) are involved in the initiation and maintenance of the berry loading process during ripening. Moreover, K+ has also been implicated in various defense mechanisms against abiotic stress. The first part of this review discusses the main negative consequences of the current climate, how they disturb the quality of grape berries at harvest and thus ultimately compromise the potential to obtain a great wine. In the second part, the essential electrical and osmotic functions of K+, which are intimately dependent on K+ transport systems, membrane energization, and cell K+ homeostasis, are presented. This knowledge will help to select crops that are better adapted to adverse environmental conditions.
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Affiliation(s)
- Houssein Monder
- BPMP, Univ Montpellier, CNRS, INRAE, Institut Agro, F-34060 Montpellier, France; (H.M.); (M.M.); (I.C.); (S.D.Z.); (N.P.)
| | - Morgan Maillard
- BPMP, Univ Montpellier, CNRS, INRAE, Institut Agro, F-34060 Montpellier, France; (H.M.); (M.M.); (I.C.); (S.D.Z.); (N.P.)
| | - Isabelle Chérel
- BPMP, Univ Montpellier, CNRS, INRAE, Institut Agro, F-34060 Montpellier, France; (H.M.); (M.M.); (I.C.); (S.D.Z.); (N.P.)
| | - Sabine Dagmar Zimmermann
- BPMP, Univ Montpellier, CNRS, INRAE, Institut Agro, F-34060 Montpellier, France; (H.M.); (M.M.); (I.C.); (S.D.Z.); (N.P.)
| | - Nadine Paris
- BPMP, Univ Montpellier, CNRS, INRAE, Institut Agro, F-34060 Montpellier, France; (H.M.); (M.M.); (I.C.); (S.D.Z.); (N.P.)
| | - Teresa Cuéllar
- CIRAD, UMR AGAP, Univ Montpellier, INRAE, Institut Agro, F-34398 Montpellier, France;
| | - Isabelle Gaillard
- BPMP, Univ Montpellier, CNRS, INRAE, Institut Agro, F-34060 Montpellier, France; (H.M.); (M.M.); (I.C.); (S.D.Z.); (N.P.)
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Dreyer I, Sussmilch FC, Fukushima K, Riadi G, Becker D, Schultz J, Hedrich R. How to Grow a Tree: Plant Voltage-Dependent Cation Channels in the Spotlight of Evolution. TRENDS IN PLANT SCIENCE 2021; 26:41-52. [PMID: 32868178 DOI: 10.1016/j.tplants.2020.07.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 07/21/2020] [Accepted: 07/23/2020] [Indexed: 06/11/2023]
Abstract
Phylogenetic analysis can be a powerful tool for generating hypotheses regarding the evolution of physiological processes. Here, we provide an updated view of the evolution of the main cation channels in plant electrical signalling: the Shaker family of voltage-gated potassium channels and the two-pore cation (K+) channel (TPC1) family. Strikingly, the TPC1 family followed the same conservative evolutionary path as one particular subfamily of Shaker channels (Kout) and remained highly invariant after terrestrialisation, suggesting that electrical signalling was, and remains, key to survival on land. We note that phylogenetic analyses can have pitfalls, which may lead to erroneous conclusions. To avoid these in the future, we suggest guidelines for analyses of ion channel evolution in plants.
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Affiliation(s)
- Ingo Dreyer
- Center for Bioinformatics, Simulation and Modeling (CBSM), Faculty of Engineering, Universidad de Talca, 2 Norte 685, Talca, Chile.
| | - Frances C Sussmilch
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs-Platz 2, D-97082 Würzburg, Germany; School of Natural Sciences, University of Tasmania, Hobart, TAS 7001, Australia
| | - Kenji Fukushima
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs-Platz 2, D-97082 Würzburg, Germany
| | - Gonzalo Riadi
- Center for Bioinformatics, Simulation and Modeling (CBSM), Faculty of Engineering, Universidad de Talca, 2 Norte 685, Talca, Chile
| | - Dirk Becker
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs-Platz 2, D-97082 Würzburg, Germany
| | - Jörg Schultz
- Department of Bioinformatics, Biozentrum, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Rainer Hedrich
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs-Platz 2, D-97082 Würzburg, Germany.
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Determining the correct stoichiometry of Kv2.1/Kv6.4 heterotetramers, functional in multiple stoichiometrical configurations. Proc Natl Acad Sci U S A 2020; 117:9365-9376. [PMID: 32284408 DOI: 10.1073/pnas.1916166117] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The electrically silent (KvS) members of the voltage-gated potassium (Kv) subfamilies Kv5, Kv6, Kv8, and Kv9 selectively modulate Kv2 subunits by forming heterotetrameric Kv2/KvS channels. Based on the reported 3:1 stoichiometry of Kv2.1/Kv9.3 channels, we tested the hypothesis that Kv2.1/Kv6.4 channels express, in contrast to the assumed 3:1, in a 2:2 stoichiometry. We investigate the Kv2.1/Kv6.4 stoichiometry using single subunit counting and functional characterization of tetrameric concatemers. For selecting the most probable stoichiometry, we introduce a model-selection method that is applicable for any multimeric complex by investigating the stoichiometry of Kv2.1/Kv6.4 channels. Weighted likelihood calculations bring rigor to a powerful technique. Using the weighted-likelihood model-selection method and analysis of electrophysiological data, we show that Kv2.1/Kv6.4 channels express, in contrast to the assumed 3:1, in a 2:2 stoichiometry. Within this stoichiometry, the Kv6.4 subunits have to be positioned alternating with Kv2.1 to express functional channels. The variability in Kv2/KvS assembly increases the diversity of heterotetrameric configurations and extends the regulatory possibilities of KvS by allowing the presence of more than one silent subunit.
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Vitali V, Jozefkowicz C, Canessa Fortuna A, Soto G, González Flecha FL, Alleva K. Cooperativity in proton sensing by PIP aquaporins. FEBS J 2018; 286:991-1002. [PMID: 30430736 DOI: 10.1111/febs.14701] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2018] [Revised: 11/05/2018] [Accepted: 11/13/2018] [Indexed: 11/28/2022]
Abstract
One of the most intriguing properties of plasma membrane intrinsic protein (PIP) aquaporins (AQPs) is their ability to modulate water transport by sensing different levels of intracellular pH through the assembly of homo- and heterotetrameric molecular species in the plasma membrane. In this work, using a phenomenological modeling approach, we demonstrate that cooperativity in PIP biological response cannot be directly attributed to a cooperative proton binding, as it is usually considered, since it could also be the consequence of a cooperative conformation transition between open and closed states of the channel. Moreover, our results show that, when mixed populations of homo- and heterotetrameric PIP channels are coexpressed in the plasma membrane of the same cell, the observed decrease in the degree of positive cooperativity would result from the simultaneous presence of molecular species with different levels of proton sensing. Indeed, the random mixing between different PIP paralogues as subunits in a single tetramer, plus the possibility of mixed populations of homo- and heterotetrameric PIP channels widen the spectrum of cooperative responses of a cell membrane. Our approach offers a deep understanding of cooperative transport of AQP channels, as members of a multiprotein family where the relevant proton binding sites of each member have not been clearly elucidated yet.
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Affiliation(s)
- Victoria Vitali
- Universidad de Buenos Aires, CONICET, Facultad de Farmacia y Bioquímica, Instituto de Química y Fisicoquímica Biológica (IQUIFIB), Argentina.,Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Departamento de Fisicomatemática, Argentina
| | - Cintia Jozefkowicz
- Instituto Nacional de Tecnología Agropecuaria, INTA, Castelar, Argentina.,CONICET, Buenos Aires, Argentina
| | - Agustina Canessa Fortuna
- Universidad de Buenos Aires, CONICET, Facultad de Farmacia y Bioquímica, Instituto de Química y Fisicoquímica Biológica (IQUIFIB), Argentina.,Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Departamento de Fisicomatemática, Argentina
| | - Gabriela Soto
- Instituto Nacional de Tecnología Agropecuaria, INTA, Castelar, Argentina.,CONICET, Buenos Aires, Argentina
| | - F Luis González Flecha
- Universidad de Buenos Aires, CONICET, Facultad de Farmacia y Bioquímica, Instituto de Química y Fisicoquímica Biológica (IQUIFIB), Argentina
| | - Karina Alleva
- Universidad de Buenos Aires, CONICET, Facultad de Farmacia y Bioquímica, Instituto de Química y Fisicoquímica Biológica (IQUIFIB), Argentina.,Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Departamento de Fisicomatemática, Argentina
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Gao YQ, Wu WH, Wang Y. The K + channel KZM2 is involved in stomatal movement by modulating inward K + currents in maize guard cells. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 92:662-675. [PMID: 28891257 DOI: 10.1111/tpj.13712] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 08/28/2017] [Accepted: 09/01/2017] [Indexed: 06/07/2023]
Abstract
Stomata are the major gates in plant leaf that allow water and gas exchange, which is essential for plant transpiration and photosynthesis. Stomatal movement is mainly controlled by the ion channels and transporters in guard cells. In Arabidopsis, the inward Shaker K+ channels, such as KAT1 and KAT2, are responsible for stomatal opening. However, the characterization of inward K+ channels in maize guard cells is limited. In the present study, we identified two KAT1-like Shaker K+ channels, KZM2 and KZM3, which were highly expressed in maize guard cells. Subcellular analysis indicated that KZM2 and KZM3 can localize at the plasma membrane. Electrophysiological characterization in HEK293 cells revealed that both KZM2 and KZM3 were inward K+ (Kin ) channels, but showing distinct channel kinetics. When expressed in Xenopus oocytes, only KZM3, but not KZM2, can mediate inward K+ currents. However, KZM2 can interact with KZM3 forming heteromeric Kin channel. In oocytes, KZM2 inhibited KZM3 channel conductance and negatively shifted the voltage dependence of KZM3. The activation of KZM2-KZM3 heteromeric channel became slower than the KZM3 channel. Patch-clamping results showed that the inward K+ currents of maize guard cells were significantly increased in the KZM2 RNAi lines. In addition, the RNAi lines exhibited faster stomatal opening after light exposure. In conclusion, the presented results demonstrate that KZM2 functions as a negative regulator to modulate the Kin channels in maize guard cells. KZM2 and KZM3 may form heteromeric Kin channel and control stomatal opening in maize.
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Affiliation(s)
- Yong-Qiang Gao
- State Key Laboratory of Plant Physiology and Biochemistry (SKLPPB), College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Wei-Hua Wu
- State Key Laboratory of Plant Physiology and Biochemistry (SKLPPB), College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Yi Wang
- State Key Laboratory of Plant Physiology and Biochemistry (SKLPPB), College of Biological Sciences, China Agricultural University, Beijing, 100193, China
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Jozefkowicz C, Sigaut L, Scochera F, Soto G, Ayub N, Pietrasanta LI, Amodeo G, González Flecha FL, Alleva K. PIP Water Transport and Its pH Dependence Are Regulated by Tetramer Stoichiometry. Biophys J 2016; 110:1312-21. [PMID: 27028641 DOI: 10.1016/j.bpj.2016.01.026] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Revised: 12/28/2015] [Accepted: 01/19/2016] [Indexed: 01/27/2023] Open
Abstract
Many plasma membrane channels form oligomeric assemblies, and heterooligomerization has been described as a distinctive feature of some protein families. In the particular case of plant plasma membrane aquaporins (PIPs), PIP1 and PIP2 monomers interact to form heterotetramers. However, the biological properties of the different heterotetrameric configurations formed by PIP1 and PIP2 subunits have not been addressed yet. Upon coexpression of tandem PIP2-PIP1 dimers in Xenopus oocytes, we can address, for the first time to our knowledge, the functional properties of single heterotetrameric species having 2:2 stoichiometry. We have also coexpressed PIP2-PIP1 dimers with PIP1 and PIP2 monomers to experimentally investigate the localization and biological activity of each tetrameric assembly. Our results show that PIP2-PIP1 heterotetramers can assemble with 3:1, 1:3, or 2:2 stoichiometry, depending on PIP1 and PIP2 relative expression in the cell. All PIP2-PIP1 heterotetrameric species localize at the plasma membrane and present the same water transport capacity. Furthermore, the contribution of any heterotetrameric assembly to the total water transport through the plasma membrane doubles the contribution of PIP2 homotetramers. Our results also indicate that plasma membrane water transport can be modulated by the coexistence of different tetrameric species and by intracellular pH. Moreover, all the tetrameric species present similar cooperativity behavior for proton sensing. These findings throw light on the functional properties of PIP tetramers, showing that they have flexible stoichiometry dependent on the quantity of PIP1 and PIP2 molecules available. This represents, to our knowledge, a novel regulatory mechanism to adjust water transport across the plasma membrane.
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Affiliation(s)
- Cintia Jozefkowicz
- Instituto de Química y Fisicoquímica Biológica Alejandro C. Paladini (IQUIFIB), Universidad de Buenos Aires, Consejo National de Investigaciones Científicas y Técnicas (UBA-CONICET), Buenos Aires, Argentina
| | - Lorena Sigaut
- Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina; Instituto de Física de Buenos Aires (IFIBA), CONICET, Ciudad Universitaria, Buenos Aires, Argentina
| | - Florencia Scochera
- Instituto de Química y Fisicoquímica Biológica Alejandro C. Paladini (IQUIFIB), Universidad de Buenos Aires, Consejo National de Investigaciones Científicas y Técnicas (UBA-CONICET), Buenos Aires, Argentina; Departamento de Fisicomatemática, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Gabriela Soto
- Instituto de Genética Ewald A. Favret, Centro de Investigación en Ciencias Veterinarias y Agronómicas, Instituto Nacional de Tecnología Agropecuaria (INTA), Castelar, Argentina
| | - Nicolás Ayub
- Instituto de Genética Ewald A. Favret, Centro de Investigación en Ciencias Veterinarias y Agronómicas, Instituto Nacional de Tecnología Agropecuaria (INTA), Castelar, Argentina
| | - Lía Isabel Pietrasanta
- Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina; Instituto de Física de Buenos Aires (IFIBA), CONICET, Ciudad Universitaria, Buenos Aires, Argentina; Centro de Microscopías Avanzadas, Facultad de Ciencias Exactas y Naturales, UBA-CONICET, Buenos Aires, Argentina
| | - Gabriela Amodeo
- Departamento de Biodiversidad y Biología Experimental, Instituto de Biodiversidad y Biología Experimental y Aplicada, Facultad de Ciencias Exactas y Naturales, UBA-CONICET, Buenos Aires, Argentina
| | - F Luis González Flecha
- Instituto de Química y Fisicoquímica Biológica Alejandro C. Paladini (IQUIFIB), Universidad de Buenos Aires, Consejo National de Investigaciones Científicas y Técnicas (UBA-CONICET), Buenos Aires, Argentina
| | - Karina Alleva
- Instituto de Química y Fisicoquímica Biológica Alejandro C. Paladini (IQUIFIB), Universidad de Buenos Aires, Consejo National de Investigaciones Científicas y Técnicas (UBA-CONICET), Buenos Aires, Argentina; Departamento de Fisicomatemática, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina.
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Wang XP, Chen LM, Liu WX, Shen LK, Wang FL, Zhou Y, Zhang Z, Wu WH, Wang Y. AtKC1 and CIPK23 Synergistically Modulate AKT1-Mediated Low-Potassium Stress Responses in Arabidopsis. PLANT PHYSIOLOGY 2016; 170:2264-77. [PMID: 26829980 PMCID: PMC4825127 DOI: 10.1104/pp.15.01493] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 01/29/2016] [Indexed: 05/19/2023]
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.
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Affiliation(s)
- Xue-Ping Wang
- 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
| | - Li-Mei Chen
- 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
| | - Wen-Xin Liu
- 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
| | - Li-Ke Shen
- 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
| | - Feng-Liu Wang
- 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
| | - Yuan Zhou
- 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
| | - Ziding Zhang
- 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
| | - Wei-Hua Wu
- 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
| | - Yi Wang
- 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
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Véry AA, Nieves-Cordones M, Daly M, Khan I, Fizames C, Sentenac H. Molecular biology of K+ transport across the plant cell membrane: what do we learn from comparison between plant species? JOURNAL OF PLANT PHYSIOLOGY 2014; 171:748-69. [PMID: 24666983 DOI: 10.1016/j.jplph.2014.01.011] [Citation(s) in RCA: 167] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2014] [Accepted: 01/30/2014] [Indexed: 05/20/2023]
Abstract
Cloning and characterizations of plant K(+) transport systems aside from Arabidopsis have been increasing over the past decade, favored by the availability of more and more plant genome sequences. Information now available enables the comparison of some of these systems between species. In this review, we focus on three families of plant K(+) transport systems that are active at the plasma membrane: the Shaker K(+) channel family, comprised of voltage-gated channels that dominate the plasma membrane conductance to K(+) in most environmental conditions, and two families of transporters, the HAK/KUP/KT K(+) transporter family, which includes some high-affinity transporters, and the HKT K(+) and/or Na(+) transporter family, in which K(+)-permeable members seem to be present in monocots only. The three families are briefly described, giving insights into the structure of their members and on functional properties and their roles in Arabidopsis or rice. The structure of the three families is then compared between plant species through phylogenic analyses. Within clusters of ortologues/paralogues, similarities and differences in terms of expression pattern, functional properties and, when known, regulatory interacting partners, are highlighted. The question of the physiological significance of highlighted differences is also addressed.
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Affiliation(s)
- Anne-Aliénor Véry
- Biochimie & Physiologie Moléculaire des Plantes, UMR 5004 CNRS/386 INRA/SupAgro Montpellier/Université Montpellier 2, Campus SupAgro-INRA, 34060 Montpellier Cedex 2, France.
| | - Manuel Nieves-Cordones
- Biochimie & Physiologie Moléculaire des Plantes, UMR 5004 CNRS/386 INRA/SupAgro Montpellier/Université Montpellier 2, Campus SupAgro-INRA, 34060 Montpellier Cedex 2, France
| | - Meriem Daly
- Biochimie & Physiologie Moléculaire des Plantes, UMR 5004 CNRS/386 INRA/SupAgro Montpellier/Université Montpellier 2, Campus SupAgro-INRA, 34060 Montpellier Cedex 2, France; Laboratoire d'Ecologie et d'Environnement, Faculté des Sciences Ben M'sik, Université Hassan II-Mohammedia, Avenue Cdt Driss El Harti, BP 7955, Sidi Othmane, Casablanca, Morocco
| | - Imran Khan
- Biochimie & Physiologie Moléculaire des Plantes, UMR 5004 CNRS/386 INRA/SupAgro Montpellier/Université Montpellier 2, Campus SupAgro-INRA, 34060 Montpellier Cedex 2, France; Department of Agronomy, University of Agriculture, Faisalabad, Pakistan
| | - Cécile Fizames
- Biochimie & Physiologie Moléculaire des Plantes, UMR 5004 CNRS/386 INRA/SupAgro Montpellier/Université Montpellier 2, Campus SupAgro-INRA, 34060 Montpellier Cedex 2, France
| | - Hervé Sentenac
- Biochimie & Physiologie Moléculaire des Plantes, UMR 5004 CNRS/386 INRA/SupAgro Montpellier/Université Montpellier 2, Campus SupAgro-INRA, 34060 Montpellier Cedex 2, France
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9
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Nieves-Cordones M, Gaillard I. Involvement of the S4-S5 linker and the C-linker domain regions to voltage-gating in plant Shaker channels: comparison with animal HCN and Kv channels. PLANT SIGNALING & BEHAVIOR 2014; 9:e972892. [PMID: 25482770 PMCID: PMC4622754 DOI: 10.4161/15592316.2014.972892] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Among the different transport systems present in plant cells, Shaker channels constitute the major pathway for K(+) in the plasma membrane. Plant Shaker channels are members of the 6 transmembrane-1 pore (6TM-1P) cation channel superfamily as the animal Shaker (Kv) and HCN channels. All these channels are voltage-gated K(+) channels: Kv channels are outward-rectifiers, opened at depolarized voltages and HCN channels are inward-rectifiers, opened by membrane hyperpolarization. Among plant Shaker channels, we can find outward-rectifiers, inward-rectifiers and also weak-rectifiers, with weak voltage dependence. Despite the absence of crystal structures of plant Shaker channels, functional analyses coupled to homology modeling, mostly based on Kv and HCN crystals, have permitted the identification of several regions contributing to plant Shaker channel gating. In the present mini-review, we make an update on the voltage-gating mechanism of plant Shaker channels which seem to be comparable to that proposed for HCN channels.
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Affiliation(s)
- Manuel Nieves-Cordones
- Biochimie et Physiologie Moléculaire des Plantes; Institut de Biologie Intégrative des Plantes; Unité Mixte de Recherche 5004 Centre National de la Recherche Scientifique/Unité Mixte de Recherche 0386 Institut National de la Recherche Agronomique/Montpellier SupAgro/Université Montpellier 2; Montpellier, France
- Correspondence to: Manuel Nieves-Cordones; , Isabelle Gaillard;
| | - Isabelle Gaillard
- Biochimie et Physiologie Moléculaire des Plantes; Institut de Biologie Intégrative des Plantes; Unité Mixte de Recherche 5004 Centre National de la Recherche Scientifique/Unité Mixte de Recherche 0386 Institut National de la Recherche Agronomique/Montpellier SupAgro/Université Montpellier 2; Montpellier, France
- Correspondence to: Manuel Nieves-Cordones; , Isabelle Gaillard;
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10
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The pH sensor of the plant K+-uptake channel KAT1 is built from a sensory cloud rather than from single key amino acids. Biochem J 2012; 442:57-63. [DOI: 10.1042/bj20111498] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The uptake of potassium ions (K+) accompanied by an acidification of the apoplasm is a prerequisite for stomatal opening. The acidification (approximately 2–2.5 pH units) is perceived by voltage-gated inward potassium channels (Kin) that then can open their pores with lower energy cost. The sensory units for extracellular pH in stomatal Kin channels are proposed to be histidines exposed to the apoplasm. However, in the Arabidopsis thaliana stomatal Kin channel KAT1, mutations in the unique histidine exposed to the solvent (His267) do not affect the pH dependency. We demonstrate in the present study that His267 of the KAT1 channel cannot sense pH changes since the neighbouring residue Phe266 shifts its pKa to undetectable values through a cation–π interaction. Instead, we show that Glu240 placed in the extracellular loop between transmembrane segments S5 and S6 is involved in the extracellular acid activation mechanism. Based on structural models we propose that this region may serve as a molecular link between the pH- and the voltage-sensor. Like Glu240, several other titratable residues could contribute to the pH-sensor of KAT1, interact with each other and even connect such residues far away from the voltage-sensor with the gating machinery of the channel.
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11
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Wang Y, He L, Li HD, Xu J, Wu WH. Potassium channel α-subunit AtKC1 negatively regulates AKT1-mediated K+ uptake in Arabidopsis roots under low-K+ stress. Cell Res 2010; 20:826-37. [DOI: 10.1038/cr.2010.74] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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12
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Riedelsberger J, Sharma T, Gonzalez W, Gajdanowicz P, Morales-Navarro SE, Garcia-Mata C, Mueller-Roeber B, González-Nilo FD, Blatt MR, Dreyer I. Distributed structures underlie gating differences between the kin channel KAT1 and the Kout channel SKOR. MOLECULAR PLANT 2010; 3:236-245. [PMID: 20007672 DOI: 10.1093/mp/ssp096] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The family of voltage-gated (Shaker-like) potassium channels in plants includes both inward-rectifying (K(in)) channels that allow plant cells to accumulate K(+) and outward-rectifying (K(out)) channels that mediate K(+) efflux. Despite their close structural similarities, K(in) and K(out) channels differ in their gating sensitivity towards voltage and the extracellular K(+) concentration. We have carried out a systematic program of domain swapping between the K(out) channel SKOR and the K(in) channel KAT1 to examine the impacts on gating of the pore regions, the S4, S5, and the S6 helices. We found that, in particular, the N-terminal part of the S5 played a critical role in KAT1 and SKOR gating. Our findings were supported by molecular dynamics of KAT1 and SKOR homology models. In silico analysis revealed that during channel opening and closing, displacement of certain residues, especially in the S5 and S6 segments, is more pronounced in KAT1 than in SKOR. From our analysis of the S4-S6 region, we conclude that gating (and K(+)-sensing in SKOR) depend on a number of structural elements that are dispersed over this approximately 145-residue sequence and that these place additional constraints on configurational rearrangement of the channels during gating.
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Affiliation(s)
- Janin Riedelsberger
- Universität Potsdam, Institut für Biochemie und Biologie, Molekularbiologie, Heisenberg-Gruppe Biophysik und Molekulare Pflanzenbiologie BPMPB, Karl-Liebknecht-Strasse 24-25, Haus 20, Potsdam-Golm, Germany
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13
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Lebaudy A, Pascaud F, Véry AA, Alcon C, Dreyer I, Thibaud JB, Lacombe B. Preferential KAT1-KAT2 heteromerization determines inward K+ current properties in Arabidopsis guard cells. J Biol Chem 2009; 285:6265-74. [PMID: 20040603 DOI: 10.1074/jbc.m109.068445] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Guard cells adjust their volume by changing their ion content due to intense fluxes that, for K(+), are believed to flow through inward or outward Shaker channels. Because Shaker channels can be homo- or heterotetramers and Arabidopsis guard cells express at least five genes encoding inward Shaker subunits, including the two major ones, KAT1 and KAT2, the molecular identity of inward Shaker channels operating therein is not yet completely elucidated. Here, we first addressed the properties of KAT1-KAT2 heteromers by expressing KAT1-KAT2 tandems in Xenopus oocytes. Then, computer analyses of the data suggested that coexpression of free KAT1 and KAT2 subunits resulted mainly in heteromeric channels made of two subunits of each type due to some preferential association of KAT1-KAT2 heterodimers at the first step of channel assembly. This was further supported by the analysis of KAT2 effect on KAT1 targeting in tobacco cells. Finally, patch-clamp recordings of native inward channels in wild-type and mutant genotypes strongly suggested that this preferential heteromerization occurs in planta and that Arabidopsis guard cell inward Shaker channels are mainly heteromers of KAT1 and KAT2 subunits.
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Affiliation(s)
- Anne Lebaudy
- Biochimie et Physiologie Moléculaire des Plantes, CNRS UMR 5004, Institut National de la Recherche Agronomique U386, Montpellier SupAgro, Université Montpellier II, Place Viala, 34060 Montpellier Cedex, France
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14
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Naso A, Dreyer I, Pedemonte L, Testa I, Gomez-Porras JL, Usai C, Mueller-Rueber B, Diaspro A, Gambale F, Picco C. The role of the C-terminus for functional heteromerization of the plant channel KDC1. Biophys J 2009; 96:4063-74. [PMID: 19450478 DOI: 10.1016/j.bpj.2009.02.055] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2008] [Revised: 02/06/2009] [Accepted: 02/17/2009] [Indexed: 12/25/2022] Open
Abstract
Voltage-gated potassium channels are formed by the assembly of four identical (homotetramer) or different (heterotetramer) subunits. Tetramerization of plant potassium channels involves the C-terminus of the protein. We investigated the role of the C-terminus of KDC1, a Shaker-like inward-rectifying K(+) channel that does not form functional homomeric channels, but participates in the formation of heteromeric complexes with other potassium alpha-subunits when expressed in Xenopus oocytes. The interaction of KDC1 with KAT1 was investigated using the yeast two-hybrid system, fluorescence and electrophysiological studies. We found that the KDC1-EGFP fusion protein is not targeted to the plasma membrane of Xenopus oocytes unless it is coexpressed with KAT1. Deletion mutants revealed that the KDC1 C-terminus is involved in heteromerization. Two domains of the C-terminus, the region downstream the putative cyclic nucleotide binding domain and the distal part of the C-terminus called K(HA) domain, contributed to a different extent to channel assembly. Whereas the first interacting region of the C-terminus was necessary for channel heteromerization, the removal of the distal K(HA) domain decreased but did not abolish the formation of heteromeric complexes. Similar results were obtained when coexpressing KDC1 with the KAT1-homolog KDC2 from carrots, thus indicating the physiological significance of the KAT1/KDC1 characterization. Electrophysiological experiments showed furthermore that the heteromerization capacity of KDC1 was negatively influenced by the presence of the enhanced green fluorescence protein fusion.
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Affiliation(s)
- Alessia Naso
- Istituto di Biofisica, Consiglio Nazionale delle Ricerche, 16149 Genoa, Italy
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15
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Dreyer I, Blatt MR. What makes a gate? The ins and outs of Kv-like K+ channels in plants. TRENDS IN PLANT SCIENCE 2009; 14:383-90. [PMID: 19540150 DOI: 10.1016/j.tplants.2009.04.001] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Revised: 04/06/2009] [Accepted: 04/07/2009] [Indexed: 05/18/2023]
Abstract
Gating of K(+) and other ion channels is 'hard-wired' within the channel protein. So it remains a puzzle how closely related channels in plants can show an unusually diverse range of biophysical properties. Gating of these channels lies at the heart of K(+) mineral nutrition, signalling, abiotic and biotic stress responses in plants. Thus, our knowledge of the molecular mechanics underpinning K(+) channel gating will be important for rational engineering of related traits in agricultural crops. Several key studies have added significantly to our understanding of channel gating in plants and have challenged current thinking about analogous processes found in animal K(+) channels. Such studies highlight how much of K(+) channel gating remains to be explored in plants.
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Affiliation(s)
- Ingo Dreyer
- Heisenberg-Group BPMPB, Institut für Biochemie und Biologie, Universität Potsdam, Karl-Liebknecht-Strasse 24/25, Potsdam-Golm, Germany
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16
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Geiger D, Becker D, Vosloh D, Gambale F, Palme K, Rehers M, Anschuetz U, Dreyer I, Kudla J, Hedrich R. Heteromeric AtKC1{middle dot}AKT1 channels in Arabidopsis roots facilitate growth under K+-limiting conditions. J Biol Chem 2009; 284:21288-95. [PMID: 19509299 DOI: 10.1074/jbc.m109.017574] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Plant growth and development is driven by osmotic processes. Potassium represents the major osmotically active cation in plants cells. The uptake of this inorganic osmolyte from the soil in Arabidopsis involves a root K(+) uptake module consisting of the two K(+) channel alpha-subunits, AKT1 and AtKC1. AKT1-mediated potassium absorption from K(+)-depleted soil was shown to depend on the calcium-sensing proteins CBL1/9 and their interacting kinase CIPK23. Here we show that upon activation by the CBL.CIPK complex in low external potassium homomeric AKT1 channels open at voltages positive of E(K), a condition resulting in cellular K(+) leakage. Although at submillimolar external potassium an intrinsic K(+) sensor reduces AKT1 channel cord conductance, loss of cytosolic potassium is not completely abolished under these conditions. Depending on channel activity and the actual potassium gradients, this channel-mediated K(+) loss results in impaired plant growth in the atkc1 mutant. Incorporation of the AtKC1 subunit into the channel complex, however, modulates the properties of the K(+) uptake module to prevent K(+) loss. Upon assembly of AKT1 and AtKC1, the activation threshold of the root inward rectifier voltage gate is shifted negative by approximately -70 mV. Additionally, the channel conductance gains a hypersensitive K(+) dependence. Together, these two processes appear to represent a safety strategy preventing K(+) loss through the uptake channels under physiological conditions. Similar growth retardation phenotypes of akt1 and atkc1 loss-of-function mutants in response to limiting K(+) supply further support such functional interdependence of AKT1 and AtKC1. Taken together, these findings suggest an essential role of AtKC1-like subunits for root K(+) uptake and K(+) homeostasis when plants experience conditions of K(+) limitation.
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Affiliation(s)
- Dietmar Geiger
- Julius-von-Sachs-Institute, Molecular Plant Physiology and Biophysics, University of Wuerzburg, Julius-von-Sachs-Platz 2, D-97082 Wuerzburg, Germany
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17
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Gajdanowicz P, Garcia-Mata C, Gonzalez W, Morales-Navarro SE, Sharma T, González-Nilo FD, Gutowicz J, Mueller-Roeber B, Blatt MR, Dreyer I. Distinct roles of the last transmembrane domain in controlling Arabidopsis K+ channel activity. THE NEW PHYTOLOGIST 2009; 182:380-391. [PMID: 19192193 DOI: 10.1111/j.1469-8137.2008.02749.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The family of voltage-gated potassium channels in plants presumably evolved from a common ancestor and includes both inward-rectifying (K(in)) channels that allow plant cells to accumulate K(+) and outward-rectifying (K(out)) channels that mediate K(+) efflux. Despite their close structural similarities, the activity of K(in) channels is largely independent of K(+) and depends only on the transmembrane voltage, whereas that of K(out) channels responds to the membrane voltage and the prevailing extracellular K(+) concentration. Gating of potassium channels is achieved by structural rearrangements within the last transmembrane domain (S6). Here we investigated the functional equivalence of the S6 helices of the K(in) channel KAT1 and the K(out) channel SKOR by domain-swapping and site-directed mutagenesis. Channel mutants and chimeras were analyzed after expression in Xenopus oocytes. We identified two discrete regions that influence gating differently in both channels, demonstrating a lack of functional complementarity between KAT1 and SKOR. Our findings are supported by molecular models of KAT1 and SKOR in the open and closed states. The role of the S6 segment in gating evolved differently during specialization of the two channel subclasses, posing an obstacle for the transfer of the K(+)-sensor from K(out) to K(in) channels.
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Affiliation(s)
- Pawel Gajdanowicz
- Universität Potsdam, Institut für Biochemie und Biologie, Heisenberg-Gruppe Biophysik und Molekulare Pflanzenbiologie, 14476 Potsdam/Golm, Germany
| | - Carlos Garcia-Mata
- Laboratory of Plant Physiology and Biophysics, IBLS Plant Sciences, Bower Building, University of Glasgow, Glasgow G12 8QQ, UK
- Laboratorio de Fisiologia Molecular e Integrativa, Institutos de Investigaciones Biologicas, Universidad Nacional de Mar del Plata, 7600 Mar del Plata, Buenos Aires, Argentina
| | - Wendy Gonzalez
- Universität Potsdam, Institut für Biochemie und Biologie, Heisenberg-Gruppe Biophysik und Molekulare Pflanzenbiologie, 14476 Potsdam/Golm, Germany
- Centro de Bioinformática y Simulación Molecular, Universidad de Talca, Casilla 721, Talca, Chile
| | | | - Tripti Sharma
- Universität Potsdam, Institut für Biochemie und Biologie, Heisenberg-Gruppe Biophysik und Molekulare Pflanzenbiologie, 14476 Potsdam/Golm, Germany
- Max-Planck Institute of Molecular Plant Physiology, 14476 Potsdam/Golm, Germany
| | | | - Jan Gutowicz
- Department of Physical Chemistry of Microorganisms, Institute of Genetics and Microbiology, University of Wrocław, 51148 Wrocław, Poland
| | - Bernd Mueller-Roeber
- Max-Planck Institute of Molecular Plant Physiology, 14476 Potsdam/Golm, Germany
- Universität Potsdam, Institut für Biochemie und Biologie, Abteilung Molekularbiologie, 14476 Potsdam/Golm, Germany
| | - Michael R Blatt
- Laboratory of Plant Physiology and Biophysics, IBLS Plant Sciences, Bower Building, University of Glasgow, Glasgow G12 8QQ, UK
| | - Ingo Dreyer
- Universität Potsdam, Institut für Biochemie und Biologie, Heisenberg-Gruppe Biophysik und Molekulare Pflanzenbiologie, 14476 Potsdam/Golm, Germany
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18
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Jeanguenin L, Lebaudy A, Xicluna J, Alcon C, Hosy E, Duby G, Michard E, Lacombe B, Dreyer I, Thibaud JB. Heteromerization of Arabidopsis Kv channel alpha-subunits: Data and prospects. PLANT SIGNALING & BEHAVIOR 2008; 3:622-5. [PMID: 19513252 PMCID: PMC2634542 DOI: 10.4161/psb.3.9.6209] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2008] [Accepted: 04/30/2008] [Indexed: 05/22/2023]
Abstract
Potassium translocation in plants is accomplished by a large variety of transport systems. Most of the available molecular information on these proteins concerns voltage-gated potassium channels (Kv channels). The Arabidopsis genome comprises nine genes encoding alpha-subunits of Kv channels. Based on knowledge of their animal homologues, and on biochemical investigations, it is broadly admitted that four such polypeptides must assemble to yield a functional Kv channel. The intrinsic functional properties of Kv channel alpha-subunits have been described by expressing them in suitable heterologous contexts where homo-tetrameric channels could be characterized. However, due to the high similarity of both the polypeptidic sequence and the structural scheme of Kv channel alpha-subunits, formation of heteromeric Kv channels by at least two types of alpha-subunits is conceivable. Several examples of such heteromeric plant Kv channels have been studied in heterologous expression systems and evidence that heteromerization actually occurs in planta has now been published. It is therefore challenging to uncover the physiological role of this heteromerization. Fine tuning of Kv channels by heteromerisation could be relevant not only to potassium transport but also to electrical signaling within the plant.
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Affiliation(s)
- Linda Jeanguenin
- Biochimie et Physiologie Moléculaire des Plantes; UMR 5004 CNRS; INRA (U 386); Montpellier, France
| | - Anne Lebaudy
- Biochimie et Physiologie Moléculaire des Plantes; UMR 5004 CNRS; INRA (U 386); Montpellier, France
| | - Jérôme Xicluna
- Biochimie et Physiologie Moléculaire des Plantes; UMR 5004 CNRS; INRA (U 386); Montpellier, France
| | - Carine Alcon
- Biochimie et Physiologie Moléculaire des Plantes; UMR 5004 CNRS; INRA (U 386); Montpellier, France
| | - Eric Hosy
- Biochimie et Physiologie Moléculaire des Plantes; UMR 5004 CNRS; INRA (U 386); Montpellier, France
| | - Geoffrey Duby
- Biochimie et Physiologie Moléculaire des Plantes; UMR 5004 CNRS; INRA (U 386); Montpellier, France
| | | | - Benoît Lacombe
- Biochimie et Physiologie Moléculaire des Plantes; UMR 5004 CNRS; INRA (U 386); Montpellier, France
| | - Ingo Dreyer
- Heisenberg-Group BPMPB; Institut für Biochemie und Biologie; Universität Potsdam; Potsdam-Golm, Germany
| | - Jean-Baptiste Thibaud
- Biochimie et Physiologie Moléculaire des Plantes; UMR 5004 CNRS; INRA (U 386); Montpellier, France
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19
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Lebaudy A, Hosy E, Simonneau T, Sentenac H, Thibaud JB, Dreyer I. Heteromeric K+ channels in plants. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2008; 54:1076-1082. [PMID: 18346194 DOI: 10.1111/j.1365-313x.2008.03479.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Voltage-gated potassium channels of plants are multimeric proteins built of four alpha-subunits. In the model plant Arabidopsis thaliana, nine genes coding for K+ channel alpha-subunits have been identified. When co-expressed in heterologous expression systems, most of them display the ability to form heteromeric K+ channels. Till now it was not clear whether plants use this potential of heteromerization to increase the functional diversity of potassium channels. Here, we designed an experimental approach employing different transgenic plant lines that allowed us to prove the existence of heteromeric K+ channels in plants. The chosen strategy might also be useful for investigating the activity and function of other multimeric channel proteins like, for instance, cyclic-nucleotide gated channels, tandem-pore K+ channels and glutamate receptor channels.
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Affiliation(s)
- Anne Lebaudy
- Biochimie et Physiologie Moléculaire des Plantes, Unité mixte de Recherche 5004, Centre National de la Recherche Scientifique/Institut National de la Recherche Agronomique (U 386)/Montpellier SupAgro/Université-Montpellier 2, France
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20
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Duby G, Hosy E, Fizames C, Alcon C, Costa A, Sentenac H, Thibaud JB. AtKC1, a conditionally targeted Shaker-type subunit, regulates the activity of plant K+ channels. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2008; 53:115-23. [PMID: 17976154 DOI: 10.1111/j.1365-313x.2007.03324.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Amongst the nine voltage-gated K(+) channel (Kv) subunits expressed in Arabidopsis, AtKC1 does not seem to form functional Kv channels on its own, and is therefore said to be silent. It has been proposed to be a regulatory subunit, and to significantly influence the functional properties of heteromeric channels in which it participates, along with other Kv channel subunits. The mechanisms underlying these properties of AtKC1 remain unknown. Here, the transient (co-)expression of AtKC1, AKT1 and/or KAT1 genes was obtained in tobacco mesophyll protoplasts, which lack endogenous inward Kv channel activity. Our experimental conditions allowed both localization of expressed polypeptides (GFP-tagging) and recording of heterologously expressed Kv channel activity (untagged polypeptides). It is shown that AtKC1 remains in the endoplasmic reticulum unless it is co-expressed with AKT1. In these conditions heteromeric AtKC1-AKT1 channels are obtained, and display functional properties different from those of homomeric AKT1 channels in the same context. In particular, the activation threshold voltage of the former channels is more negative than that of the latter ones. Also, it is proposed that AtKC1-AKT1 heterodimers are preferred to AKT1-AKT1 homodimers during the process of tetramer assembly. Similar results are obtained upon co-expression of AtKC1 with KAT1. The whole set of data provides evidence that AtKC1 is a conditionally-targeted Kv subunit, which probably downregulates the physiological activity of other Kv channel subunits in Arabidopsis.
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Affiliation(s)
- Geoffrey Duby
- Biochimie et Physiologie Moléculaire des plantes, CNRS(UMR-5004)-INRA-SupAgro-UM2, 2 place Viala, F-34060 Montpellier cedex 1, France
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21
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Bregante M, Yang Y, Formentin E, Carpaneto A, Schroeder JI, Gambale F, Lo Schiavo F, Costa A. KDC1, a carrot Shaker-like potassium channel, reveals its role as a silent regulatory subunit when expressed in plant cells. PLANT MOLECULAR BIOLOGY 2008; 66:61-72. [PMID: 17955184 DOI: 10.1007/s11103-007-9252-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2007] [Accepted: 10/06/2007] [Indexed: 05/13/2023]
Abstract
The Shaker potassium channels are tetrameric proteins formed by the assembly of four alpha-subunits. The oligomerization can occur among both homo- and hetero-alpha-subunits. KDC1 is a carrot Shaker-like potassium channel expressed in the epidermis of plantlet roots and the protoderm of somatic embryos. KDC1 was previously characterised electrophysiologically in CHO and Xenopus oocytes cells, but the experiments performed in these systems did not provide conclusive evidence that KDC1 forms a functional homomeric channel in plant cells. In this report, we show that KDC1 localizes to the plasma membrane of root cells in transgenic tobacco plants transformed with a KDC1::GFP fusion construct. In tobacco mesophyll protoplasts, transiently transformed with KDC1::GFP, KDC1 was present on the endomembrane and the protoplasts did not show any inward potassium current, as demonstrated by patch-clamp experiments. The co-expression of KDC1::GFP with the Arabidopsis thaliana potassium channel AKT1 in tobacco mesophyll protoplasts has the effect of shifting KDC1 localization from endomembranes to the plasma membrane. Patch-clamp experiments performed on tobacco mesophyll protoplasts expressing AKT1 alone or in combination with KDC1::GFP showed voltage-activated inward potassium currents with different properties. In particular, the addition of Zn2+ to the bath solution induced a clear decrease of the potassium currents in protoplasts transformed with AKT1 alone, whereas a current potentiation (indicative of KDC1 presence) was observed in protoplasts co-transformed with AKT1 + KDC1::GFP. Split-Ubiquitin assay experiments performed in yeast cells confirmed the interaction between AKT1 and KDC1.
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Affiliation(s)
- Monica Bregante
- Istituto di Biofisica-CNR, Via De Marini 6, Genova 16149, Italy
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22
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Picco C, Naso A, Soliani P, Gambale F. The zinc binding site of the Shaker channel KDC1 from Daucus carota. Biophys J 2007; 94:424-33. [PMID: 17890387 PMCID: PMC2157247 DOI: 10.1529/biophysj.107.114009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
KDC1 is a voltage-dependent Shaker-like potassium channel subunit cloned from Daucus carota which produces conductive channels in Xenopus oocytes only when coexpressed with other plant Shaker potassium subunits, such as KAT1 from Arabidopsis thaliana. External Zn(2+) determines a potentiation of the current mediated by the dimeric construct KDC1-KAT1, which has been ascribed to zinc binding at a site comprising three histidines located at the S3-S4 (H161, H162) and S5-S6 (H224) linkers of KDC1. Here we demonstrate that also glutamate 164, located in close proximity of the KDC1 S4 segment, is an essential component of the zinc-binding site. On the contrary, glutamate 159, located in symmetrical position with respect to E164 in the sequence E(159)XHHXE(164) but more distant from the voltage sensor, does not play any role in zinc binding. The effects of Zn(2+) can be expressed as a "shift" of the gating parameters along the voltage axis. Kinetic modeling shows that Zn(2+) slows the closing kinetics of KDC1-KAT1 without affecting the opening kinetics. Possibly, zinc affects the movement of the voltage sensor in and out of the membrane phase through electrostatic modification of a site close to the voltage sensor.
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Affiliation(s)
- Cristiana Picco
- Istituto di Biofisica, Consiglio Nazionale delle Ricerche, Genoa, Italy.
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