1
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Blatt MR. A charged existence: A century of transmembrane ion transport in plants. Plant Physiol 2024; 195:79-110. [PMID: 38163639 PMCID: PMC11060664 DOI: 10.1093/plphys/kiad630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 11/01/2023] [Indexed: 01/03/2024]
Abstract
If the past century marked the birth of membrane transport as a focus for research in plants, the past 50 years has seen the field mature from arcane interest to a central pillar of plant physiology. Ion transport across plant membranes accounts for roughly 30% of the metabolic energy consumed by a plant cell, and it underpins virtually every aspect of plant biology, from mineral nutrition, cell expansion, and development to auxin polarity, fertilization, plant pathogen defense, and senescence. The means to quantify ion flux through individual transporters, even single channel proteins, became widely available as voltage clamp methods expanded from giant algal cells to the fungus Neurospora crassa in the 1970s and the cells of angiosperms in the 1980s. Here, I touch briefly on some key aspects of the development of modern electrophysiology with a focus on the guard cells of stomata, now without dispute the premier plant cell model for ion transport and its regulation. Guard cells have proven to be a crucible for many technical and conceptual developments that have since emerged into the mainstream of plant science. Their study continues to provide fundamental insights and carries much importance for the global challenges that face us today.
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Affiliation(s)
- Michael R Blatt
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Bower Building, Glasgow G12 8QQ, UK
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2
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Horaruang W, Klejchová M, Carroll W, Silva-Alvim FAL, Waghmare S, Papanatsiou M, Amtmann A, Hills A, Alvim JC, Blatt MR, Zhang B. Engineering a K + channel 'sensory antenna' enhances stomatal kinetics, water use efficiency and photosynthesis. Nat Plants 2022; 8:1262-1274. [PMID: 36266492 DOI: 10.1038/s41477-022-01255-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 09/12/2022] [Indexed: 06/16/2023]
Abstract
Stomata of plant leaves open to enable CO2 entry for photosynthesis and close to reduce water loss via transpiration. Compared with photosynthesis, stomata respond slowly to fluctuating light, reducing assimilation and water use efficiency. Efficiency gains are possible without a cost to photosynthesis if stomatal kinetics can be accelerated. Here we show that clustering of the GORK channel, which mediates K+ efflux for stomatal closure in the model plant Arabidopsis, arises from binding between the channel voltage sensors, creating an extended 'sensory antenna' for channel gating. Mutants altered in clustering affect channel gating to facilitate K+ flux, accelerate stomatal movements and reduce water use without a loss in biomass. Our findings identify the mechanism coupling channel clustering with gating, and they demonstrate the potential for engineering of ion channels native to the guard cell to enhance stomatal kinetics and improve water use efficiency without a cost in carbon fixation.
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Affiliation(s)
- Wijitra Horaruang
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
- Faculty of Science and Arts, Burapha University, Chanthaburi Campus, Chanthaburi, Thailand
| | - Martina Klejchová
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | - William Carroll
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | | | - Sakharam Waghmare
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | - Maria Papanatsiou
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | - Anna Amtmann
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | - Adrian Hills
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | - Jonas Chaves Alvim
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK
| | - Michael R Blatt
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow, UK.
| | - Ben Zhang
- School of Life Sciences, Shanxi University, Taiyuan City, China
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3
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Abstract
Potassium (K+) channels serve a wide range of functions in plants from mineral nutrition and osmotic balance to turgor generation for cell expansion and guard cell aperture control. Plant K+ channels are members of the superfamily of voltage-dependent K+ channels, or Kv channels, that include the Shaker channels first identified in fruit flies (Drosophila melanogaster). Kv channels have been studied in depth over the past half century and are the best-known of the voltage-dependent channels in plants. Like the Kv channels of animals, the plant Kv channels are regulated over timescales of milliseconds by conformational mechanisms that are commonly referred to as gating. Many aspects of gating are now well established, but these channels still hold some secrets, especially when it comes to the control of gating. How this control is achieved is especially important, as it holds substantial prospects for solutions to plant breeding with improved growth and water use efficiencies. Resolution of the structure for the KAT1 K+ channel, the first channel from plants to be crystallized, shows that many previous assumptions about how the channels function need now to be revisited. Here, I strip the plant Kv channels bare to understand how they work, how they are gated by voltage and, in some cases, by K+ itself, and how the gating of these channels can be regulated by the binding with other protein partners. Each of these features of plant Kv channels has important implications for plant physiology.
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Affiliation(s)
- Cécile Lefoulon
- Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow G12 8QQ, Scotland
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4
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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5
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Ródenas R, Ragel P, Nieves-Cordones M, Martínez-Martínez A, Amo J, Lara A, Martínez V, Quintero FJ, Pardo JM, Rubio F. Insights into the mechanisms of transport and regulation of the arabidopsis high-affinity K+ transporter HAK51. Plant Physiol 2021; 185:1860-1874. [PMID: 33595056 PMCID: PMC8133630 DOI: 10.1093/plphys/kiab028] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 01/11/2021] [Indexed: 05/02/2023]
Abstract
The high-affinity K+ transporter HAK5 from Arabidopsis (Arabidopsis thaliana) is essential for K+ acquisition and plant growth at low micromolar K+ concentrations. Despite its functional relevance in plant nutrition, information about functional domains of HAK5 is scarce. Its activity is enhanced by phosphorylation via the AtCIPK23/AtCBL1-9 complex. Based on the recently published three-dimensionalstructure of the bacterial ortholog KimA from Bacillus subtilis, we have modeled AtHAK5 and, by a mutational approach, identified residues G67, Y70, G71, D72, D201, and E312 as essential for transporter function. According to the structural model, residues D72, D201, and E312 may bind K+, whereas residues G67, Y70, and G71 may shape the selective filter for K+, which resembles that of K+shaker-like channels. In addition, we show that phosphorylation of residue S35 by AtCIPK23 is required for reaching maximal transport activity. Serial deletions of the AtHAK5 C-terminus disclosed the presence of an autoinhibitory domain located between residues 571 and 633 together with an AtCIPK23-dependent activation domain downstream of position 633. Presumably, autoinhibition of AtHAK5 is counteracted by phosphorylation of S35 by AtCIPK23. Our results provide a molecular model for K+ transport and describe CIPK-CBL-mediated regulation of plant HAK transporters.
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Affiliation(s)
- Reyes Ródenas
- Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura, Consejo Superior de Investigaciones Científicas, Campus de Espinardo, 30100 Murcia, Spain
- Present address: Plant Science Research Laboratory (LRSV), UMR5546 CNRS/Université Toulouse 3, 24 chemin de Borde Rouge, 31320 Auzeville-Tolosane, France
| | - Paula Ragel
- Instituto de Bioquímica Vegetal y Fotosíntesis, cic-Cartuja, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, 41092 Sevilla, Spain
- Present address: Centre for Organismal Studies (COS), Department of Cell Biology, Heidelberg University, Heidelberg, Germany
| | - Manuel Nieves-Cordones
- Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura, Consejo Superior de Investigaciones Científicas, Campus de Espinardo, 30100 Murcia, Spain
| | - Almudena Martínez-Martínez
- Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura, Consejo Superior de Investigaciones Científicas, Campus de Espinardo, 30100 Murcia, Spain
| | - Jesús Amo
- Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura, Consejo Superior de Investigaciones Científicas, Campus de Espinardo, 30100 Murcia, Spain
| | - Alberto Lara
- Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura, Consejo Superior de Investigaciones Científicas, Campus de Espinardo, 30100 Murcia, Spain
| | - Vicente Martínez
- Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura, Consejo Superior de Investigaciones Científicas, Campus de Espinardo, 30100 Murcia, Spain
| | - Francisco J Quintero
- Instituto de Bioquímica Vegetal y Fotosíntesis, cic-Cartuja, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, 41092 Sevilla, Spain
| | - Jose M Pardo
- Instituto de Bioquímica Vegetal y Fotosíntesis, cic-Cartuja, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, 41092 Sevilla, Spain
| | - Francisco Rubio
- Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura, Consejo Superior de Investigaciones Científicas, Campus de Espinardo, 30100 Murcia, Spain
- Author for communication:
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6
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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 Plant Sci 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] [What about the content of this article? (0)] [Affiliation(s)] [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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7
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Klejchová M, Hills A, Blatt MR. Predicting the unexpected in stomatal gas exchange: not just an open-and-shut case. Biochem Soc Trans 2020; 48:881-889. [PMID: 32453378 PMCID: PMC7329339 DOI: 10.1042/bst20190632] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Revised: 05/01/2020] [Accepted: 05/04/2020] [Indexed: 12/22/2022]
Abstract
Plant membrane transport, like transport across all eukaryotic membranes, is highly non-linear and leads to interactions with characteristics so complex that they defy intuitive understanding. The physiological behaviour of stomatal guard cells is a case in point in which, for example, mutations expected to influence stomatal closing have profound effects on stomatal opening and manipulating transport across the vacuolar membrane affects the plasma membrane. Quantitative mathematical modelling is an essential tool in these circumstances, both to integrate the knowledge of each transport process and to understand the consequences of their manipulation in vivo. Here, we outline the OnGuard modelling environment and its use as a guide to predicting the emergent properties arising from the interactions between non-linear transport processes. We summarise some of the recent insights arising from OnGuard, demonstrate its utility in interpreting stomatal behaviour, and suggest ways in which the OnGuard environment may facilitate 'reverse-engineering' of stomata to improve water use efficiency and carbon assimilation.
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Affiliation(s)
- Martina Klejchová
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Bower Building, Glasgow G12 8QQ, U.K
| | - Adrian Hills
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Bower Building, Glasgow G12 8QQ, U.K
| | - Michael R. Blatt
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Bower Building, Glasgow G12 8QQ, U.K
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8
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Ma W, Yang G, Xiao Y, Zhao X, Wang J. ABA-dependent K + flux is one of the important features of the drought response that distinguishes Catalpa from two different habitats. Plant Signal Behav 2020; 15:1735755. [PMID: 32141360 PMCID: PMC7194386 DOI: 10.1080/15592324.2020.1735755] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 02/22/2020] [Accepted: 02/24/2020] [Indexed: 06/01/2023]
Abstract
Abscisic acid (ABA)-induced stomatal closure can improve drought tolerance in higher plants. However, the relationship between ABA-related ion flux and improved drought resistance in the roots of woody plants is unclear. To investigate this relationship, we employed a noninvasive micro-test technique (NMT) to detect potassium (K+) flux in Catalpa fargesii and C. fargesii f. duclouxii after treatment with polyethylene glycol (PEG) and ABA. PEG treatment slightly increased the free proline content in both Catalpa species. However, simultaneous treatment with ABA and PEG resulted in a large increase in free proline content. Treatment with PEG led to a significant increase in K+ efflux, and both ABA and tetraethylammonium (TEA, a K+ channel inhibitor) blocked this efflux under short-term (1 d) and long-term (7 d) drought conditions. Furthermore, we detected SKOR (stelar K+ outward-rectifying channel) gene expression in roots, and the results showed that PEG significantly increased SKOR expression in C. fargesii f. duclouxii, but SKOR expression was inhibited by ABA in Catalpa fargesii. These findings indicate that ABA improves drought tolerance by inhibiting K+ efflux in Catalpa, but distinct ABA response patterns exist. Drought-tolerant species have better potassium retention are dependent on ABA, and can accumulate more proline than other species. SKOR is also ABA-dependent and sensitive to ABA, and K+ flux is a target of the ABA-mediated drought response.
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Affiliation(s)
- Wenjun Ma
- State Key Laboratory of Tree Genetics and Breeding, Beijing, PR China
- Research Institute of Forestry, Chinese Academy of Forestry, Beijing, PR China
- Key Laboratory of Tree Breeding and Cultivation, State Forestry and Grassland Administration, Beijing, PR China
- National Innovation Alliance of Catalapa Bungei, Beijing, PR China
| | - Guijuan Yang
- State Key Laboratory of Tree Genetics and Breeding, Beijing, PR China
- Research Institute of Forestry, Chinese Academy of Forestry, Beijing, PR China
- Key Laboratory of Tree Breeding and Cultivation, State Forestry and Grassland Administration, Beijing, PR China
- National Innovation Alliance of Catalapa Bungei, Beijing, PR China
| | - Yao Xiao
- State Key Laboratory of Tree Genetics and Breeding, Beijing, PR China
- Research Institute of Forestry, Chinese Academy of Forestry, Beijing, PR China
- Key Laboratory of Tree Breeding and Cultivation, State Forestry and Grassland Administration, Beijing, PR China
- National Innovation Alliance of Catalapa Bungei, Beijing, PR China
| | - Xiyang Zhao
- Northeast Forestry University, Harbin, PR China
| | - Junhui Wang
- State Key Laboratory of Tree Genetics and Breeding, Beijing, PR China
- Research Institute of Forestry, Chinese Academy of Forestry, Beijing, PR China
- Key Laboratory of Tree Breeding and Cultivation, State Forestry and Grassland Administration, Beijing, PR China
- National Innovation Alliance of Catalapa Bungei, Beijing, PR China
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9
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Fernie AR, Bachem CWB, Helariutta Y, Neuhaus HE, Prat S, Ruan YL, Stitt M, Sweetlove LJ, Tegeder M, Wahl V, Sonnewald S, Sonnewald U. Synchronization of developmental, molecular and metabolic aspects of source-sink interactions. Nat Plants 2020; 6:55-66. [PMID: 32042154 DOI: 10.1038/s41477-020-0590-x] [Citation(s) in RCA: 76] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Accepted: 12/28/2019] [Indexed: 05/02/2023]
Abstract
Plants have evolved a multitude of strategies to adjust their growth according to external and internal signals. Interconnected metabolic and phytohormonal signalling networks allow adaption to changing environmental and developmental conditions and ensure the survival of species in fluctuating environments. In agricultural ecosystems, many of these adaptive responses are not required or may even limit crop yield, as they prevent plants from realizing their fullest potential. By lifting source and sink activities to their maximum, massive yield increases can be foreseen, potentially closing the future yield gap resulting from an increasing world population and the transition to a carbon-neutral economy. To do so, a better understanding of the interplay between metabolic and developmental processes is required. In the past, these processes have been tackled independently from each other, but coordinated efforts are required to understand the fine mechanics of source-sink relations and thus optimize crop yield. Here, we describe approaches to design high-yielding crop plants utilizing strategies derived from current metabolic concepts and our understanding of the molecular processes determining sink development.
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Affiliation(s)
- Alisdair R Fernie
- Max Planck Institute of Molecular Plant Physiology, Potsdam, Germany.
| | | | - Yrjö Helariutta
- The Sainsbury Laboratory, University of Cambridge, Cambridge, UK
| | - H Ekkehard Neuhaus
- University of Kaiserslautern Pflanzenphysiologie, Kaiserslautern, Germany
| | - Salomé Prat
- Department of Plant Molecular Genetics, Centro Nacional de Biotecnología-CSIC, Madrid, Spain
| | - Yong-Ling Ruan
- School of Environmental & Life Sciences, University of Newcastle, Callaghan, New South Wales, Australia
| | - Mark Stitt
- Max Planck Institute of Molecular Plant Physiology, Potsdam, Germany
| | - Lee J Sweetlove
- Department of Plant Sciences, University of Oxford, Oxford, UK
| | - Mechthild Tegeder
- School of Biological Sciences, Washington State University, Pullman, WA, USA
| | - Vanessa Wahl
- Max Planck Institute of Molecular Plant Physiology, Potsdam, Germany
| | - Sophia Sonnewald
- Division of Biochemistry, Department of Biology, University of Erlangen-Nürnberg, Erlangen, Germany.
| | - Uwe Sonnewald
- Division of Biochemistry, Department of Biology, University of Erlangen-Nürnberg, Erlangen, Germany.
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11
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12
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Karnik R, Waghmare S, Zhang B, Larson E, Lefoulon C, Gonzalez W, Blatt MR. Commandeering Channel Voltage Sensors for Secretion, Cell Turgor, and Volume Control. Trends Plant Sci 2017; 22:81-95. [PMID: 27818003 PMCID: PMC5224186 DOI: 10.1016/j.tplants.2016.10.006] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2016] [Revised: 10/06/2016] [Accepted: 10/07/2016] [Indexed: 05/20/2023]
Abstract
Control of cell volume and osmolarity is central to cellular homeostasis in all eukaryotes. It lies at the heart of the century-old problem of how plants regulate turgor, mineral and water transport. Plants use strongly electrogenic H+-ATPases, and the substantial membrane voltages they foster, to drive solute accumulation and generate turgor pressure for cell expansion. Vesicle traffic adds membrane surface and contributes to wall remodelling as the cell grows. Although a balance between vesicle traffic and ion transport is essential for cell turgor and volume control, the mechanisms coordinating these processes have remained obscure. Recent discoveries have now uncovered interactions between conserved subsets of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins that drive the final steps in secretory vesicle traffic and ion channels that mediate in inorganic solute uptake. These findings establish the core of molecular links, previously unanticipated, that coordinate cellular homeostasis and cell expansion.
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Affiliation(s)
- Rucha Karnik
- Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Sakharam Waghmare
- Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Ben Zhang
- Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Emily Larson
- Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Cécile Lefoulon
- Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Wendy Gonzalez
- Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile
| | - Michael R Blatt
- Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow, G12 8QQ, UK.
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13
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Riedelsberger J, Dreyer I, Gonzalez W. Outward Rectification of Voltage-Gated K+ Channels Evolved at Least Twice in Life History. PLoS One 2015; 10:e0137600. [PMID: 26356684 DOI: 10.1371/journal.pone.0137600] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 07/15/2015] [Indexed: 11/19/2022] Open
Abstract
Voltage-gated potassium (K+) channels are present in all living systems. Despite high structural similarities in the transmembrane domains (TMD), this K+ channel type segregates into at least two main functional categories—hyperpolarization-activated, inward-rectifying (Kin) and depolarization-activated, outward-rectifying (Kout) channels. Voltage-gated K+ channels sense the membrane voltage via a voltage-sensing domain that is connected to the conduction pathway of the channel. It has been shown that the voltage-sensing mechanism is the same in Kin and Kout channels, but its performance results in opposite pore conformations. It is not known how the different coupling of voltage-sensor and pore is implemented. Here, we studied sequence and structural data of voltage-gated K+ channels from animals and plants with emphasis on the property of opposite rectification. We identified structural hotspots that alone allow already the distinction between Kin and Kout channels. Among them is a loop between TMD S5 and the pore that is very short in animal Kout, longer in plant and animal Kin and the longest in plant Kout channels. In combination with further structural and phylogenetic analyses this finding suggests that outward-rectification evolved twice and independently in the animal and plant kingdom.
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Yang G, Sentenac H, Véry AA, Su Y. Complex interactions among residues within pore region determine the K+ dependence of a KAT1-type potassium channel AmKAT1. Plant J 2015; 83:401-12. [PMID: 26032087 DOI: 10.1111/tpj.12891] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Revised: 05/12/2015] [Accepted: 05/26/2015] [Indexed: 05/26/2023]
Abstract
KAT1-type channels mediate K(+) influx into guard cells that enables stomatal opening. In this study, a KAT1-type channel AmKAT1 was cloned from the xerophyte Ammopiptanthus mongolicus. In contrast to most KAT1-type channels, its activation is strongly dependent on external K(+) concentration, so it can be used as a model to explore the mechanism for the K(+) -dependent gating of KAT1-type channels. Domain swapping between AmKAT1 and KAT1 reveals that the S5-pore-S6 region controls the K(+) dependence of AmKAT1, and residue substitutions show that multiple residues within the S5-Pore linker and Pore are involved in its K(+) -dependent gating. Importantly, complex interactions occur among these residues, and it is these interactions that determine its K(+) dependence. Finally, we analyzed the potential mechanism for the K(+) dependence of AmKAT1, which could originate from the requirement of K(+) occupancy in the selectivity filter to maintain its conductive conformation. These results provide new insights into the molecular basis of the K(+) -dependent gating of KAT1-type channels.
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Affiliation(s)
- Guangzhe Yang
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, No. 71, East Beijing Road, Nanjing, 210008, China
| | - 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
| | - 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
| | - Yanhua Su
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, No. 71, East Beijing Road, Nanjing, 210008, China
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Lefoulon C, Karnik R, Honsbein A, Gutla PV, Grefen C, Riedelsberger J, Poblete T, Dreyer I, Gonzalez W, Blatt MR. Voltage-sensor transitions of the inward-rectifying K+ channel KAT1 indicate a latching mechanism biased by hydration within the voltage sensor. Plant Physiol 2014; 166:960-75. [PMID: 25185120 PMCID: PMC4213121 DOI: 10.1104/pp.114.244319] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The Kv-like (potassium voltage-dependent) K(+) channels at the plasma membrane, including the inward-rectifying KAT1 K(+) channel of Arabidopsis (Arabidopsis thaliana), are important targets for manipulating K(+) homeostasis in plants. Gating modification, especially, has been identified as a promising means by which to engineer plants with improved characteristics in mineral and water use. Understanding plant K(+) channel gating poses several challenges, despite many similarities to that of mammalian Kv and Shaker channel models. We have used site-directed mutagenesis to explore residues that are thought to form two electrostatic countercharge centers on either side of a conserved phenylalanine (Phe) residue within the S2 and S3 α-helices of the voltage sensor domain (VSD) of Kv channels. Consistent with molecular dynamic simulations of KAT1, we show that the voltage dependence of the channel gate is highly sensitive to manipulations affecting these residues. Mutations of the central Phe residue favored the closed KAT1 channel, whereas mutations affecting the countercharge centers favored the open channel. Modeling of the macroscopic current kinetics also highlighted a substantial difference between the two sets of mutations. We interpret these findings in the context of the effects on hydration of amino acid residues within the VSD and with an inherent bias of the VSD, when hydrated around a central Phe residue, to the closed state of the channel.
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Affiliation(s)
- Cécile Lefoulon
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.)
| | - Rucha Karnik
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.)
| | - Annegret Honsbein
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.)
| | - Paul Vijay Gutla
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.)
| | - Christopher Grefen
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.)
| | - Janin Riedelsberger
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.)
| | - Tomás Poblete
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.)
| | - Ingo Dreyer
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.)
| | - Wendy Gonzalez
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.)
| | - Michael R Blatt
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom (C.L., R.K., A.H., P.V.G., C.G., M.R.B.);Centro de Bioinformatica y Simulacion Molecular, Universidad de Talca, Casilla 721, Talca, Chile (J.R., T.P., W.G.);University of Potsdam, Biochemistry and Biology Group BPMBP, D14476 Golm, Germany (J.R., I.D., W.G.); andCentre for Biotechnology and Plant Genomics UPM, Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, 28223 Pozuelo de Alacon, Madrid, Spain (I.D.)
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Nieves-Cordones M, Chavanieu A, Jeanguenin L, Alcon C, Szponarski W, Estaran S, Chérel I, Zimmermann S, Sentenac H, Gaillard I. Distinct amino acids in the C-linker domain of the Arabidopsis K+ channel KAT2 determine its subcellular localization and activity at the plasma membrane. Plant Physiol 2014; 164:1415-29. [PMID: 24406792 PMCID: PMC3938630 DOI: 10.1104/pp.113.229757] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Accepted: 01/05/2014] [Indexed: 05/18/2023]
Abstract
Shaker K(+) channels form the major K(+) conductance of the plasma membrane in plants. They are composed of four subunits arranged around a central ion-conducting pore. The intracellular carboxy-terminal region of each subunit contains several regulatory elements, including a C-linker region and a cyclic nucleotide-binding domain (CNBD). The C-linker is the first domain present downstream of the sixth transmembrane segment and connects the CNBD to the transmembrane core. With the aim of identifying the role of the C-linker in the Shaker channel properties, we performed subdomain swapping between the C-linker of two Arabidopsis (Arabidopsis thaliana) Shaker subunits, K(+) channel in Arabidopsis thaliana2 (KAT2) and Arabidopsis thaliana K(+) rectifying channel1 (AtKC1). These two subunits contribute to K(+) transport in planta by forming heteromeric channels with other Shaker subunits. However, they display contrasting behavior when expressed in tobacco mesophyll protoplasts: KAT2 forms homotetrameric channels active at the plasma membrane, whereas AtKC1 is retained in the endoplasmic reticulum when expressed alone. The resulting chimeric/mutated constructs were analyzed for subcellular localization and functionally characterized. We identified two contiguous amino acids, valine-381 and serine-382, located in the C-linker carboxy-terminal end, which prevent KAT2 surface expression when mutated into the equivalent residues from AtKC1. Moreover, we demonstrated that the nine-amino acid stretch 312TVRAASEFA320 that composes the first C-linker α-helix located just below the pore is a crucial determinant of KAT2 channel activity. A KAT2 C-linker/CNBD three-dimensional model, based on animal HCN (for Hyperpolarization-activated, cyclic nucleotide-gated K(+)) channels as structure templates, has been built and used to discuss the role of the C-linker in plant Shaker inward channel structure and function.
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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, 34060 Montpellier cedex 2, France (M.N.-C., L.J., C.A., W.S., I.C., S.Z., H.S., I.G.); and
- Institut des Biomolécules Max Mousseron, Unité Mixte de Recherche 5247, Faculté de Pharmacie, 34093 Montpellier cedex, France (A.C., S.E.)
| | - Alain Chavanieu
- 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, 34060 Montpellier cedex 2, France (M.N.-C., L.J., C.A., W.S., I.C., S.Z., H.S., I.G.); and
- Institut des Biomolécules Max Mousseron, Unité Mixte de Recherche 5247, Faculté de Pharmacie, 34093 Montpellier cedex, France (A.C., S.E.)
| | | | - Carine Alcon
- 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, 34060 Montpellier cedex 2, France (M.N.-C., L.J., C.A., W.S., I.C., S.Z., H.S., I.G.); and
- Institut des Biomolécules Max Mousseron, Unité Mixte de Recherche 5247, Faculté de Pharmacie, 34093 Montpellier cedex, France (A.C., S.E.)
| | - Wojciech Szponarski
- 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, 34060 Montpellier cedex 2, France (M.N.-C., L.J., C.A., W.S., I.C., S.Z., H.S., I.G.); and
- Institut des Biomolécules Max Mousseron, Unité Mixte de Recherche 5247, Faculté de Pharmacie, 34093 Montpellier cedex, France (A.C., S.E.)
| | - Sebastien Estaran
- 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, 34060 Montpellier cedex 2, France (M.N.-C., L.J., C.A., W.S., I.C., S.Z., H.S., I.G.); and
- Institut des Biomolécules Max Mousseron, Unité Mixte de Recherche 5247, Faculté de Pharmacie, 34093 Montpellier cedex, France (A.C., S.E.)
| | - Isabelle Chérel
- 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, 34060 Montpellier cedex 2, France (M.N.-C., L.J., C.A., W.S., I.C., S.Z., H.S., I.G.); and
- Institut des Biomolécules Max Mousseron, Unité Mixte de Recherche 5247, Faculté de Pharmacie, 34093 Montpellier cedex, France (A.C., S.E.)
| | - Sabine Zimmermann
- 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, 34060 Montpellier cedex 2, France (M.N.-C., L.J., C.A., W.S., I.C., S.Z., H.S., I.G.); and
- Institut des Biomolécules Max Mousseron, Unité Mixte de Recherche 5247, Faculté de Pharmacie, 34093 Montpellier cedex, France (A.C., S.E.)
| | - Hervé Sentenac
- 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, 34060 Montpellier cedex 2, France (M.N.-C., L.J., C.A., W.S., I.C., S.Z., H.S., I.G.); and
- Institut des Biomolécules Max Mousseron, Unité Mixte de Recherche 5247, Faculté de Pharmacie, 34093 Montpellier cedex, France (A.C., S.E.)
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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 Signal Behav 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] [What about the content of this article? (0)] [Affiliation(s)] [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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Abstract
Since the first recordings of single potassium channel activities in the plasma membrane of guard cells more than 25 years ago, patch-clamp studies discovered a variety of ion channels in all cell types and plant species under inspection. Their properties differed in a cell type- and cell membrane-dependent manner. Guard cells, for which the existence of plant potassium channels was initially documented, advanced to a versatile model system for studying plant ion channel structure, function, and physiology. Interestingly, one of the first identified potassium-channel genes encoding the Shaker-type channel KAT1 was shown to be highly expressed in guard cells. KAT1-type channels from Arabidopsis thaliana and its homologs from other species were found to encode the K+-selective inward rectifiers that had already been recorded in early patch-clamp studies with guard cells. Within the genome era, additional Arabidopsis Shaker-type channels appeared. All nine members of the Arabidopsis Shaker family are localized at the plasma membrane, where they either operate as inward rectifiers, outward rectifiers, weak voltage-dependent channels, or electrically silent, but modulatory subunits. The vacuole membrane, in contrast, harbors a set of two-pore K+ channels. Just very recently, two plant anion channel families of the SLAC/SLAH and ALMT/QUAC type were identified. SLAC1/SLAH3 and QUAC1 are expressed in guard cells and mediate Slow- and Rapid-type anion currents, respectively, that are involved in volume and turgor regulation. Anion channels in guard cells and other plant cells are key targets within often complex signaling networks. Here, the present knowledge is reviewed for the plant ion channel biology. Special emphasis is drawn to the molecular mechanisms of channel regulation, in the context of model systems and in the light of evolution.
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Affiliation(s)
- Rainer Hedrich
- University of Wuerzburg, Institute for Molecular Plant Physiology and Biophysics, Wuerzburg, Germany; and King Saud University, Riyadh, Saudi Arabia
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González W, Riedelsberger J, Morales-navarro S, Caballero J, Alzate-morales J, González-nilo F, Dreyer I. 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] [What about the content of this article? (0)] [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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Abstract
Potassium (K(+) ) is the most abundant inorganic cation in plant cells. Unlike animals, plants lack sodium/potassium exchangers. Instead, plant cells have developed unique transport systems for K(+) accumulation and release. An essential role in potassium uptake and efflux is played by potassium channels. Since the first molecular characterization of K(+) channels from Arabidopsis thaliana in 1992, a large number of studies on plant potassium channels have been conducted. Potassium channels are considered to be one of the best characterized class of membrane proteins in plants. Nevertheless, knowledge on plant potassium channels is still incomplete. This minireview focuses on recent developments in the research of potassium transport in plants with a strong focus on voltage-gated potassium channels.
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Affiliation(s)
- Ingo Dreyer
- Centro de Biotecnologia y Genomica de Plantas, Universidad Politécnica de Madrid, Madrid, Spain.
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22
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Gajdanowicz P, Michard E, Sandmann M, Rocha M, Corrêa LG, Ramírez-Aguilar SJ, Gomez-Porras JL, González W, Thibaud JB, van Dongen JT, Dreyer I. Potassium (K+) gradients serve as a mobile energy source in plant vascular tissues. Proc Natl Acad Sci U S A 2011; 108:864-9. [PMID: 21187374 DOI: 10.1073/pnas.1009777108] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The essential mineral nutrient potassium (K(+)) is the most important inorganic cation for plants and is recognized as a limiting factor for crop yield and quality. Nonetheless, it is only partially understood how K(+) contributes to plant productivity. K(+) is used as a major active solute to maintain turgor and to drive irreversible and reversible changes in cell volume. K(+) also plays an important role in numerous metabolic processes, for example, by serving as an essential cofactor of enzymes. Here, we provide evidence for an additional, previously unrecognized role of K(+) in plant growth. By combining diverse experimental approaches with computational cell simulation, we show that K(+) circulating in the phloem serves as a decentralized energy storage that can be used to overcome local energy limitations. Posttranslational modification of the phloem-expressed Arabidopsis K(+) channel AKT2 taps this "potassium battery," which then efficiently assists the plasma membrane H(+)-ATPase in energizing the transmembrane phloem (re)loading processes.
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Abstract
Potassium (K(+) ) flux into plant cells is a well-characterized ion transport phenomenon. By contrast, little is known about the mechanisms and regulation of K(+) flux from the cell. Here, we present a radioisotopic analysis of K(+) fluxes from roots of intact barley (Hordeum vulgare), in the context of recent discoveries in the molecular biology and electrophysiology of this process. Plants were labelled with (42)K(+), and kinetics of its release from roots were monitored at low (0.1 mM) or high (1.0 mM) external K concentration, [K(+)](ext), and with the application of channel modulators and nutrient shifts. At 0.1 (but not 1.0) mM [K(+)], where K(+) efflux is thought to be mediated by K(+)-outward-rectifying channels, (42)K(+) efflux was inhibited by the channel blockers barium (Ba(2+)), caesium (Cs(+)), tetraethylammonium (TEA(+)), and lanthanum (La(3+)). Ammonium and nitrate (10 mM) stimulated and inhibited (42)K(+) efflux, respectively, while 10 mM [K(+)](ext) or [Rb(+) ](ext) decreased it. No evidence for the involvement of ATP-binding cassettes, nonselective cation channels, or active K(+)-efflux pumps was found. Our study provides new evidence for the thermodynamic transition between high- and low-affinity transport, from the efflux perspective, identifying the operation of channels at low [K(+)], and the cessation of transmembrane efflux at high [K(+)].
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Affiliation(s)
- Devrim Coskun
- Department of Biological Sciences, University of Toronto, 1265 Military Trail, Toronto, ON, Canada
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Hedrich R, Anschütz U, Becker D. Biology of Plant Potassium Channels. In: Murphy AS, Schulz B, Peer W, editors. The Plant Plasma Membrane. Berlin: Springer Berlin Heidelberg; 2011. pp. 253-74. [DOI: 10.1007/978-3-642-13431-9_11] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
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Garcia-Mata C, Wang J, Gajdanowicz P, Gonzalez W, Hills A, Donald N, Riedelsberger J, Amtmann A, Dreyer I, Blatt MR. A minimal cysteine motif required to activate the SKOR K+ channel of Arabidopsis by the reactive oxygen species H2O2. J Biol Chem 2010; 285:29286-94. [PMID: 20605786 DOI: 10.1074/jbc.m110.141176] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Reactive oxygen species (ROS) are essential for development and stress signaling in plants. They contribute to plant defense against pathogens, regulate stomatal transpiration, and influence nutrient uptake and partitioning. Although both Ca(2+) and K(+) channels of plants are known to be affected, virtually nothing is known of the targets for ROS at a molecular level. Here we report that a single cysteine (Cys) residue within the Kv-like SKOR K(+) channel of Arabidopsis thaliana is essential for channel sensitivity to the ROS H(2)O(2). We show that H(2)O(2) rapidly enhanced current amplitude and activation kinetics of heterologously expressed SKOR, and the effects were reversed by the reducing agent dithiothreitol (DTT). Both H(2)O(2) and DTT were active at the outer face of the membrane and current enhancement was strongly dependent on membrane depolarization, consistent with a H(2)O(2)-sensitive site on the SKOR protein that is exposed to the outside when the channel is in the open conformation. Cys substitutions identified a single residue, Cys(168) located within the S3 α-helix of the voltage sensor complex, to be essential for sensitivity to H(2)O(2). The same Cys residue was a primary determinant for current block by covalent Cys S-methioylation with aqueous methanethiosulfonates. These, and additional data identify Cys(168) as a critical target for H(2)O(2), and implicate ROS-mediated control of the K(+) channel in regulating mineral nutrient partitioning within the plant.
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Affiliation(s)
- Carlos Garcia-Mata
- Laboratory of Plant Physiology and Biophysics, Faculty of Biomedical and Life Sciences, Plant Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
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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] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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Sato A, Gambale F, Dreyer I, Uozumi N. Modulation of the Arabidopsis KAT1 channel by an activator of protein kinase C in Xenopus laevis oocytes. FEBS J 2010; 277:2318-28. [DOI: 10.1111/j.1742-4658.2010.07647.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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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. Mol 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] [What about the content of this article? (0)] [Affiliation(s)] [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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Sato A, Sato Y, Fukao Y, Fujiwara M, Umezawa T, Shinozaki K, Hibi T, Taniguchi M, Miyake H, Goto D, Uozumi N. Threonine at position 306 of the KAT1 potassium channel is essential for channel activity and is a target site for ABA-activated SnRK2/OST1/SnRK2.6 protein kinase. Biochem J 2009; 424:439-48. [DOI: 10.1042/bj20091221] [Citation(s) in RCA: 279] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The Arabidopsis thaliana K+ channel KAT1 has been suggested to have a key role in mediating the aperture of stomata pores on the surface of plant leaves. Although the activity of KAT1 is thought to be regulated by phosphorylation, the endogenous pathway and the primary target site for this modification remained unknown. In the present study, we have demonstrated that the C-terminal region of KAT1 acts as a phosphorylation target for the Arabidopsis calcium-independent ABA (abscisic acid)-activated protein kinase SnRK2.6 (Snf1-related protein kinase 2.6). This was confirmed by LC-MS/MS (liquid chromatography tandem MS) analysis, which showed that Thr306 and Thr308 of KAT1 were modified by phosphorylation. The role of these specific residues was examined by single point mutations and measurement of KAT1 channel activities in Xenopus oocyte and yeast systems. Modification of Thr308 had minimal effect on KAT1 activity. On the other hand, modification of Thr306 reduced the K+ transport uptake activity of KAT1 in both systems, indicating that Thr306 is responsible for the functional regulation of KAT1. These results suggest that negative regulation of KAT1 activity, required for stomatal closure, probably occurs by phosphorylation of KAT1 Thr306 by the stress-activated endogenous SnRK2.6 protein kinase.
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Dreyer I, Blatt MR. What makes a gate? The ins and outs of Kv-like K+ channels in plants. Trends Plant Sci 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] [What about the content of this article? (0)] [Affiliation(s)] [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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