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Jiang C, Belfield EJ, Cao Y, Smith JAC, Harberd NP. An Arabidopsis soil-salinity-tolerance mutation confers ethylene-mediated enhancement of sodium/potassium homeostasis. THE PLANT CELL 2013; 25:3535-52. [PMID: 24064768 PMCID: PMC3809548 DOI: 10.1105/tpc.113.115659] [Citation(s) in RCA: 128] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 08/28/2013] [Accepted: 09/03/2013] [Indexed: 05/18/2023]
Abstract
High soil Na concentrations damage plants by increasing cellular Na accumulation and K loss. Excess soil Na stimulates ethylene-induced soil-salinity tolerance, the mechanism of which we here define via characterization of an Arabidopsis thaliana mutant displaying transpiration-dependent soil-salinity tolerance. This phenotype is conferred by a loss-of-function allele of ethylene overproducer1 (ETO1; mutant alleles of which cause increased production of ethylene). We show that lack of ETO1 function confers soil-salinity tolerance through improved shoot Na/K homeostasis, effected via the ethylene resistant1-constitutive triple response1 ethylene signaling pathway. Under transpiring conditions, lack of ETO1 function reduces root Na influx and both stelar and xylem sap Na concentrations, thereby restricting root-to-shoot delivery of Na. These effects are associated with increased accumulation of respiratory burst oxidase homolog F (RBOHF)-dependent reactive oxygen species in the root stele. Additionally, lack of ETO1 function leads to significant enhancement of tissue K status by an RBOHF-independent mechanism associated with elevated high-affinity K(+) TRANSPORTER5 transcript levels. We conclude that ethylene promotes soil-salinity tolerance via improved Na/K homeostasis mediated by RBOHF-dependent regulation of Na accumulation and RBOHF-independent regulation of K accumulation.
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Affiliation(s)
- Caifu Jiang
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom
| | - Eric J. Belfield
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom
| | - Yi Cao
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom
| | - J. Andrew C. Smith
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom
| | - Nicholas P. Harberd
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom
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102
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Coskun D, Britto DT, Li M, Oh S, Kronzucker HJ. Capacity and plasticity of potassium channels and high-affinity transporters in roots of barley and Arabidopsis. PLANT PHYSIOLOGY 2013; 162:496-511. [PMID: 23553635 PMCID: PMC3641226 DOI: 10.1104/pp.113.215913] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Accepted: 03/31/2013] [Indexed: 05/03/2023]
Abstract
The role of potassium (K(+)) transporters in high- and low-affinity K(+) uptake was examined in roots of intact barley (Hordeum vulgare) and Arabidopsis (Arabidopsis thaliana) plants by use of (42)K radiotracing, electrophysiology, pharmacology, and mutant analysis. Comparisons were made between results from barley and five genotypes of Arabidopsis, including single and double knockout mutants for the high-affinity transporter, AtHAK5, and the Shaker-type channel, AtAKT1. In Arabidopsis, steady-state K(+) influx at low external K(+) concentration ([K(+)]ext = 22.5 µm) was predominantly mediated by AtAKT1 when high-affinity transport was inhibited by ammonium, whereas in barley, by contrast, K(+) channels could not operate below 100 µm. Withdrawal of ammonium resulted in an immediate and dramatic stimulation of K(+) influx in barley, indicating a shift from active to passive K(+) uptake at low [K(+)]ext and yielding fluxes as high as 36 µmol g (root fresh weight)(-1) h(-1) at 5 mm [K(+)]ext, among the highest transporter-mediated K(+) fluxes hitherto reported. This ammonium-withdrawal effect was also established in all Arabidopsis lines (the wild types, atakt1, athak5, and athak5 atakt1) at low [K(+)]ext, revealing the concerted involvement of several transport systems. The ammonium-withdrawal effect coincided with a suppression of K(+) efflux and a significant hyperpolarization of the plasma membrane in all genotypes except athak5 atakt1, could be sustained over 24 h, and resulted in increased tissue K(+) accumulation. We discuss key differences and similarities in K(+) acquisition between two important model systems and reveal novel aspects of K(+) transport in planta.
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Affiliation(s)
- Devrim Coskun
- Department of Biological Sciences, University of Toronto, Toronto, Ontario, Canada M1C 1A4
| | - Dev T. Britto
- Department of Biological Sciences, University of Toronto, Toronto, Ontario, Canada M1C 1A4
| | - Mingyuan Li
- Department of Biological Sciences, University of Toronto, Toronto, Ontario, Canada M1C 1A4
| | - Saehong Oh
- Department of Biological Sciences, University of Toronto, Toronto, Ontario, Canada M1C 1A4
| | - Herbert J. Kronzucker
- Department of Biological Sciences, University of Toronto, Toronto, Ontario, Canada M1C 1A4
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103
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Sharma T, Dreyer I, Riedelsberger J. The role of K(+) channels in uptake and redistribution of potassium in the model plant Arabidopsis thaliana. FRONTIERS IN PLANT SCIENCE 2013; 4:224. [PMID: 23818893 PMCID: PMC3694395 DOI: 10.3389/fpls.2013.00224] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Accepted: 06/09/2013] [Indexed: 05/17/2023]
Abstract
Potassium (K(+)) is inevitable for plant growth and development. It plays a crucial role in the regulation of enzyme activities, in adjusting the electrical membrane potential and the cellular turgor, in regulating cellular homeostasis and in the stabilization of protein synthesis. Uptake of K(+) from the soil and its transport to growing organs is essential for a healthy plant development. Uptake and allocation of K(+) are performed by K(+) channels and transporters belonging to different protein families. In this review we summarize the knowledge on the versatile physiological roles of plant K(+) channels and their behavior under stress conditions in the model plant Arabidopsis thaliana.
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Affiliation(s)
- Tripti Sharma
- Molecular Biology, Institute for Biochemistry and Biology, University of PotsdamPotsdam, Germany
- IMPRS-PMPG, Max-Planck Institute of Molecular Plant PhysiologyPotsdam, Germany
| | - Ingo Dreyer
- Centro de Biotecnologia y Genomica de Plantas, Universidad Politécnica de MadridMadrid, Spain
- *Correspondence: Ingo Dreyer, Plant Biophysics, Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid, Campus de Montegancedo, Carretera M-40, km 37.7, Pozuelo de Alarcón, Madrid E-28223, Spain e-mail:
| | - Janin Riedelsberger
- Molecular Biology, Institute for Biochemistry and Biology, University of PotsdamPotsdam, Germany
- IMPRS-PMPG, Max-Planck Institute of Molecular Plant PhysiologyPotsdam, Germany
- Janin Riedelsberger, Molecular Biology, Institute for Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Str. 24/25, House 20, D-14476 Potsdam, Germany e-mail:
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Caballero F, Botella MA, Rubio L, Fernández JA, Martínez V, Rubio F. A Ca(2+)-sensitive system mediates low-affinity K(+) uptake in the absence of AKT1 in Arabidopsis plants. PLANT & CELL PHYSIOLOGY 2012; 53:2047-59. [PMID: 23054389 DOI: 10.1093/pcp/pcs140] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
K(+) acquisition by Arabidopsis roots is mainly mediated by the high-affinity K(+) transporter AtHAK5 and the inward-rectifier K(+) channel AtAKT1. This model is probably universal to plants. Mutant plants lacking these two systems (athak5,atakt1) take up K(+) and grow when the external K(+) concentration is above a certain level, indicating that an additional transport system may compensate for the absence of AtHAK5 and AtAKT1. Here we describe that this alternative system is essential for providing sufficient K(+) to sustain growth of athak5,atakt1 plants. This system is especially sensitive to Ca(2+), Mg(2+), Ba(2+) and La(3+), it transports Cs(+) and its activity is reduced by cyclic nucleotides. These results suggest that a Ca(2+)-permeable voltage-independent non-selective cation channel, probably belonging to the cyclic nucleotide gated channel (CNGC) family, may provide the pathway for K(+) uptake in athak5,atakt1 plants. The genes encoding the two members of the CNGC family that have been described as mediating root K(+) uptake, AtCNGC3 and AtCNGC10, are not up-regulated in athak5,atakt1 plants, excluding overexpression of these genes as a compensatory mechanism. On the other hand, an increased driving force for K(+) in athak5,atakt1 plants due to a hyperpolarization of the membrane potential of its root cells is also discarded. The identification of this unknown system may provide tools to improve plant K(+) nutrition in conditions where AtAKT1 functionality is reduced, such as under salinity. In addition, this system may constitute an important pathway for accumulation of toxic cations such as Cs(+) or radiocesium ((137)Cs(+)), and could play a role in phytoremediation.
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Affiliation(s)
- Fernando Caballero
- Departamento de Nutrición, CEBAS-CSIC, Campus de Espinardo, 30100 Murcia, Spain
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105
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106
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Borghi M, Rus A, Salt DE. Loss-of-function of Constitutive Expresser of Pathogenesis Related Genes5 affects potassium homeostasis in Arabidopsis thaliana. PLoS One 2011; 6:e26360. [PMID: 22046278 PMCID: PMC3203115 DOI: 10.1371/journal.pone.0026360] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Accepted: 09/25/2011] [Indexed: 11/24/2022] Open
Abstract
Here, we demonstrate that the reduction in leaf K(+) observed in a mutant previously identified in an ionomic screen of fast neutron mutagenized Arabidopsis thaliana is caused by a loss-of-function allele of CPR5, which we name cpr5-3. This observation establishes low leaf K(+) as a new phenotype for loss-of-function alleles of CPR5. We investigate the factors affecting this low leaf K(+) in cpr5 using double mutants defective in salicylic acid (SA) and jasmonic acid (JA) signalling, and by gene expression analysis of various channels and transporters. Reciprocal grafting between cpr5 and Col-0 was used to determine the relative importance of the shoot and root in causing the low leaf K(+) phenotype of cpr5. Our data show that loss-of-function of CPR5 in shoots primarily determines the low leaf K(+) phenotype of cpr5, though the roots also contribute to a lesser degree. The low leaf K(+) phenotype of cpr5 is independent of the elevated SA and JA known to occur in cpr5. In cpr5 expression of genes encoding various Cyclic Nucleotide Gated Channels (CNGCs) are uniquely elevated in leaves. Further, expression of HAK5, encoding the high affinity K(+) uptake transporter, is reduced in roots of cpr5 grown with high or low K(+) supply. We suggest a model in which low leaf K(+) in cpr5 is driven primarily by enhanced shoot-to-root K(+) export caused by a constitutive activation of the expression of various CNGCs. This activation may enhance K(+) efflux, either indirectly via enhanced cytosolic Ca(2+) and/or directly by increased K(+) transport activity. Enhanced shoot-to-root K(+) export may also cause the reduced expression of HAK5 observed in roots of cpr5, leading to a reduction in uptake of K(+). All ionomic data presented is publically available at www.ionomicshub.org.
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Affiliation(s)
- Monica Borghi
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana, United States of America
| | - Ana Rus
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana, United States of America
| | - David E. Salt
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana, United States of America
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107
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Alvarez-Pizarro JC, Gomes-Filho E, Prisco JT, Grossi-de-Sá MF, de Oliveira-Neto OB. NH(4)(+)-stimulated low-K(+) uptake is associated with the induction of H(+) extrusion by the plasma membrane H(+)-ATPase in sorghum roots under K(+) deficiency. JOURNAL OF PLANT PHYSIOLOGY 2011; 168:1617-1626. [PMID: 21458104 DOI: 10.1016/j.jplph.2011.03.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2010] [Revised: 02/25/2011] [Accepted: 03/01/2011] [Indexed: 05/27/2023]
Abstract
The effect of external inorganic nitrogen and K(+) content on K(+) uptake from low-K(+) solutions and plasma membrane (PM) H(+)-ATPase activity of sorghum roots was studied. Plants were grown for 15 days in full-nutrient solutions containing 0.2 or 1.4mM K(+) and inorganic nitrogen as NO(3)(-), NO(3)(-)/NH(4)(+) or NH(4)(+) and then starved of K(+) for 24, 48 and 72 h. NH(4)(+) in full nutrient solution significantly affected the uptake efficiency and accumulation of K(+), and this effect was less pronounced at the high K(+) concentration. In contrast, the translocation rate of K(+) to the shoot was not altered. Depletion assays showed that plants grown with NH(4)(+) more efficiently depleted the external K(+) and reached higher initial rates of low-K(+) uptake than plants grown with NO(3)(-). One possible influence of K(+) content of shoot, but not of roots, on K(+) uptake was evidenced. Enhanced K(+)-uptake capacity was correlated with the induction of H(+) extrusion by PM H(+)-ATPase. In plants grown in high K(+) solutions, the increase in the active H(+) gradient was associated with an increase of the PM H(+)-ATPase protein concentration. In contrast, in plants grown in solutions containing 0.2mM K(+), only the initial rate of H(+)-pumping and ATP hydrolysis were affected. Under these conditions, two specific isoforms of PM H(+)-ATPase were detected, independent of the nitrogen source and deficiency period. No change in enzyme activity was observed in NO(3)(-)-grown plants. The results suggest that K(+) homeostasis in NH(4)(+)-grown sorghum plants may be regulated by a high capacity for K(+) uptake, which is dependent upon the H(+)-pumping activity of PM H(+)-ATPase.
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Affiliation(s)
- Juan Carlos Alvarez-Pizarro
- Departamento de Bioquímica e Biologia Molecular and Instituto Nacional de Ciência e Tecnologia em Salinidade (INCTSal/CNPq), Universidade Federal do Ceará, Caixa Postal 6039, 60455-900 Fortaleza, Ceará, Brazil
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108
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Alemán F, Nieves-Cordones M, Martínez V, Rubio F. Root K(+) acquisition in plants: the Arabidopsis thaliana model. PLANT & CELL PHYSIOLOGY 2011; 52:1603-12. [PMID: 21771865 DOI: 10.1093/pcp/pcr096] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
K(+) is an essential macronutrient required by plants to complete their life cycle. It fulfills important functions and it is widely used as a fertilizer to increase crop production. Thus, the identification of the systems involved in K(+) acquisition by plants has always been a research goal as it may eventually produce molecular tools to enhance crop productivity further. This review is focused on the recent findings on the systems involved in K(+) acquisition. From Epstein's pioneering work >40 years ago, K(+) uptake was considered to consist of a high- and a low-affinity component. The subsequent molecular approaches identified genes encoding K(+) transport systems which could be involved in the first step of K(+) uptake at the plant root. Insights into the regulation of these genes and the proteins that they encode have also been gained in recent studies. A demonstration of the role of the two main K(+) uptake systems at the root, AtHKA5 and AKT1, has been possible with the study of Arabidopsis thaliana T-DNA insertion lines that knock out these genes. AtHAK5 was revealed as the only uptake system at external concentrations <10 μM. Between 10 and 200 μM both AtHAK5 and AKT1 contribute to K(+) acquisition. At external concentrations >500 μM, AtHAK5 is not relevant and AKT1's contribution to K(+) uptake becomes more important. At 10 mM K(+), unidentified systems may provide sufficient K(+) uptake for plant growth.
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Affiliation(s)
- Fernando Alemán
- Centro de Edafología y Biología Aplicada del Segura-CSIC, Campus de Espinardo, 30100 Murcia, Spain
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109
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Conde A, Chaves MM, Gerós H. Membrane transport, sensing and signaling in plant adaptation to environmental stress. PLANT & CELL PHYSIOLOGY 2011; 52:1583-602. [PMID: 21828102 DOI: 10.1093/pcp/pcr107] [Citation(s) in RCA: 144] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Plants are generally well adapted to a wide range of environmental conditions. Even though they have notably prospered in our planet, stressful conditions such as salinity, drought and cold or heat, which are increasingly being observed worldwide in the context of the ongoing climate changes, limit their growth and productivity. Behind the remarkable ability of plants to cope with these stresses and still thrive, sophisticated and efficient mechanisms to re-establish and maintain ion and cellular homeostasis are involved. Among the plant arsenal to maintain homeostasis are efficient stress sensing and signaling mechanisms, plant cell detoxification systems, compatible solute and osmoprotectant accumulation and a vital rearrangement of solute transport and compartmentation. The key role of solute transport systems and signaling proteins in cellular homeostasis is addressed in the present work. The full understanding of the plant cell complex defense mechanisms under stress may allow for the engineering of more tolerant plants or the optimization of cultivation practices to improve yield and productivity, which is crucial at the present time as food resources are progressively scarce.
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Affiliation(s)
- Artur Conde
- Centro de Investigacão e de Tecnologias Agro-Ambientais e Biológicas, Portugal
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110
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Ardie SW, Nishiuchi S, Liu S, Takano T. Ectopic expression of the K+ channel β subunits from Puccinellia tenuiflora (KPutB1) and rice (KOB1) alters K+ homeostasis of yeast and Arabidopsis. Mol Biotechnol 2011; 48:76-86. [PMID: 21108023 DOI: 10.1007/s12033-010-9349-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
In this study, we cloned a cDNA for the K+ channel β subunit from the halophyte Puccinellia tenuiflora and named it KPutB1. KPutB1 was preferentially expressed in the roots and was transiently induced by K+-starvation, salt stress, or the combination of both stresses. By yeast two-hybrid assay, we demonstrated that KPutB1 interacts with PutAKT1, α subunit of an AKT1-type K+ channel of P. tenuiflora. The functional relevance of this interaction on K+-nutrition was investigated by co-expression experiments in yeast under various ionic conditions, and K+ channel α and β subunit homologues from rice (OsAKT1 and KOB1, respectively) were included for comparison. Yeast co-expressing PutAKT1 and the β subunits (KPutB1 and KOB1) had better growth and higher K+-uptake ability than yeast expressing PutAKT1 alone. In contrast, yeast co-expressing the β subunits (KPutB1 and KOB1) with OsAKT1 had slower growth and lower K+ uptake than yeast expressing OsAKT1 alone. Arabidopsis plants over-expressing the K+ channel β subunit of P. tenuiflora or rice showed increased shoot K+ content and decreased root Na+ content under control, 75 mM NaCl, and K+-starvation stress conditions. These results suggest that ectopic expression of the K+ channel β subunit could alter K+ and Na+ homeostasis in plants.
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Affiliation(s)
- Sintho Wahyuning Ardie
- Asian Natural Environmental Science Center (ANESC), The University of Tokyo, 1-1-1 Midori-cho, Nishitokyo-shi, Tokyo 188-0002, Japan
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111
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Pardo JM, Rubio F. Na+ and K+ Transporters in Plant Signaling. SIGNALING AND COMMUNICATION IN PLANTS 2011. [DOI: 10.1007/978-3-642-14369-4_3] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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112
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Tsay YF, Ho CH, Chen HY, Lin SH. Integration of nitrogen and potassium signaling. ANNUAL REVIEW OF PLANT BIOLOGY 2011; 62:207-26. [PMID: 21495843 DOI: 10.1146/annurev-arplant-042110-103837] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Sensing and responding to soil nutrient fluctuations are vital for the survival of higher plants. Over the past few years, great progress has been made in our understanding of nitrogen and potassium signaling. Key components of the signaling pathways including sensors, kinases, miRNA, ubiquitin ligases, and transcriptional factors. These components mediate the transcriptional responses, root-architecture changes, and uptake-activity modulation induced by nitrate, ammonium, and potassium in the soil solution. Integration of these responses allows plants to compete for limited nutrients and to survive under nutrient deficiency or toxic nutrient excess. A future challenge is to extend the present fragmented sets of data to a comprehensive signaling network. Then, such knowledge and the accompanying molecular tools can be applied to improve the efficiency of nutrient utilization in crops.
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Affiliation(s)
- Yi-Fang Tsay
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.
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113
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Abstract
Sodium (Na) toxicity is one of the most formidable challenges for crop production world-wide. Nevertheless, despite decades of intensive research, the pathways of Na(+) entry into the roots of plants under high salinity are still not definitively known. Here, we review critically the current paradigms in this field. In particular, we explore the evidence supporting the role of nonselective cation channels, potassium transporters, and transporters from the HKT family in primary sodium influx into plant roots, and their possible roles elsewhere. We furthermore discuss the evidence for the roles of transporters from the NHX and SOS families in intracellular Na(+) partitioning and removal from the cytosol of root cells. We also review the literature on the physiology of Na(+) fluxes and cytosolic Na(+) concentrations in roots and invite critical interpretation of seminal published data in these areas. The main focus of the review is Na(+) transport in glycophytes, but reference is made to literature on halophytes where it is essential to the analysis.
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Rubio F, Arévalo L, Caballero F, Botella MA, Rubio JS, García-Sánchez F, Martínez V. Systems involved in K+ uptake from diluted solutions in pepper plants as revealed by the use of specific inhibitors. JOURNAL OF PLANT PHYSIOLOGY 2010; 167:1494-1499. [PMID: 20691498 DOI: 10.1016/j.jplph.2010.05.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Revised: 05/13/2010] [Accepted: 05/27/2010] [Indexed: 05/29/2023]
Abstract
Here, the contribution of the HAK1 transporter, the AKT1 channel and a putative AtCHX13 homolog to K(+) uptake in the high-affinity range of concentrations in pepper plants was examined. The limited development of molecular tools in pepper plants precluded a reverse genetics study in this species. By contrast, in the model plant Arabidopsis thaliana, these type of studies have shown that NH(4)(+) and Ba(2+) may be used as specific inhibitors of the two K(+) uptake systems to dissect their contribution in species in which, as in pepper, specific mutant lines are not available. By using these inhibitors together with Na(+) and Cs(+), the relative contributions of CaHAK1, CaAKT1 and a putative AtCHX13 homolog to K(+) acquisition from diluted solutions under different regimens of K(+) supply were studied. The results showed that, in plants completely starved of K(+), the gene encoding CaHAK1 was highly expressed and this system is a major contributor to K(+) uptake. However, K(+) concentrations as low as 50μM reduced CaHAK1 expression and the CaAKT1 channel came into play, participating together with CaHAK1 in K(+) absorption. The contribution of a putative AtCHX13 homolog seemed to be low under this low K(+) supply, but it cannot be ruled out that at higher K(+) concentrations this system participates in K(+) uptake. Studies of this type allow extension of the tools developed in model plants to understand nutrition in important crops.
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Affiliation(s)
- Francisco Rubio
- Departamento de Nutrición, Centro de Edafología y Biología Aplicada del Segura-CSIC, Campus de Espinardo, 30100 Murcia, Spain.
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115
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116
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Ardie SW, Liu S, Takano T. Expression of the AKT1-type K(+) channel gene from Puccinellia tenuiflora, PutAKT1, enhances salt tolerance in Arabidopsis. PLANT CELL REPORTS 2010; 29:865-74. [PMID: 20532513 DOI: 10.1007/s00299-010-0872-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2010] [Revised: 04/20/2010] [Accepted: 05/10/2010] [Indexed: 05/03/2023]
Abstract
Potassium channels are important for many physiological functions in plants, one of which is to regulate plant adaptation to stress conditions. In this study, a K(+) channel PutAKT1 cDNA was isolated from the salt-tolerant plant Puccinellia tenuiflora. A phylogenetic analysis showed that PutAKT1 belongs to the AKT1-subfamily in the Shaker K(+) channel family. PutAKT1 was localized in the plasma membrane and it was preferentially expressed in the roots. The expression of PutAKT1 was induced by K(+)-starvation stress in the roots and was not down-regulated by the presence of excess Na(+). Arabidopsis plants over-expressing PutAKT1 showed enhanced salt tolerance compared to wild-type plants as shown by their shoot phenotype and dry weight. Expression of PutAKT1 increased the K(+) content of Arabidopsis under normal, K(+)-starvation, and NaCl-stress conditions. Arabidopsis expressing PutAKT1 also showed a decrease in Na(+) accumulation both in the shoot and in the root. These results suggest that PutAKT1 is involved in mediating K(+) uptake (i) both in low- and in high-affinity K(+) uptake range, and (ii) unlike its homologs in rice, even under salt-stress condition.
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Affiliation(s)
- Sintho Wahyuning Ardie
- Asian Natural Environmental Science Center (ANESC), The University of Tokyo, 1-1-1 Midori-Cho, Nishitokyo, Tokyo 188-0002, Japan
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117
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Pyo YJ, Gierth M, Schroeder JI, Cho MH. High-affinity K(+) transport in Arabidopsis: AtHAK5 and AKT1 are vital for seedling establishment and postgermination growth under low-potassium conditions. PLANT PHYSIOLOGY 2010; 153:863-75. [PMID: 20413648 PMCID: PMC2879780 DOI: 10.1104/pp.110.154369] [Citation(s) in RCA: 146] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2010] [Accepted: 04/16/2010] [Indexed: 05/17/2023]
Abstract
Potassium (K(+)) is a major plant nutrient required for growth and development. It is generally accepted that plant roots absorb K(+) through uptake systems operating at low concentrations (high-affinity transport) and/or high external concentrations (low-affinity transport). To understand the molecular basis of high-affinity K(+) uptake in Arabidopsis (Arabidopsis thaliana), we analyzed loss-of-function mutants in AtHAK5 and AKT1, two transmembrane proteins active in roots. Compared with the wild type under NH(4)(+)-free growth conditions, athak5 mutant plants exhibited growth defects at 10 mum K(+), but at K(+) concentrations of 20 mum and above, athak5 mutants were visibly indistinguishable from the wild type. While germination, scored as radicle emergence, was only slightly decreased in athak5 akt1 double mutants on low-K(+) medium, double mutants failed to grow on medium containing up to 100 mum K(+) and growth was impaired at concentrations up to 450 mum K(+). Moreover, transfer of 3-d-old plants from high to low K(+) concentrations led to growth defects and leaf chlorosis at 10 mum K(+) in athak5 akt1 double mutant plants. Determination of Rb(+)(K(+)) uptake kinetics in wild-type and mutant roots using rubidium ((86)Rb(+)) as a tracer for K(+) revealed that high-affinity Rb(+)(K(+)) uptake into roots is almost completely abolished in double mutants and impaired in single mutants. These results strongly indicate that AtHAK5 and AKT1 are the two major, physiologically relevant molecular entities mediating high-affinity K(+) uptake into roots during seedling establishment and postgermination growth and that residual Rb(+)(K(+)) uptake measured in athak5 akt1 double mutant roots is insufficient to enable plant growth.
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Affiliation(s)
| | | | | | - Myeon Haeng Cho
- Department of Biology, Yonsei University, Seoul 120–749, Republic of Korea (Y.J.P., M.H.C.); Department of Botany II, University of Cologne, 50674 Cologne, Germany (M.G.); Division of Biological Sciences, Cell and Developmental Biology Section, University of California San Diego, La Jolla, California 92093–0116 (J.I.S.)
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Rubio F, Alemán F, Nieves-Cordones M, Martínez V. Studies on Arabidopsis athak5, atakt1 double mutants disclose the range of concentrations at which AtHAK5, AtAKT1 and unknown systems mediate K uptake. PHYSIOLOGIA PLANTARUM 2010; 139:220-8. [PMID: 20088908 DOI: 10.1111/j.1399-3054.2010.01354.x] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The high-affinity K(+) transporter AtHAK5 and the inward-rectifier K(+) channel AtAKT1 have been described to contribute to K(+) uptake in Arabidopsis thaliana. Studies with T-DNA insertion lines showed that both systems participate in the high-affinity range of concentrations and only AtAKT1 in the low-affinity range. However the contribution of other systems could not be excluded with the information and plant material available. The results presented here with a double knock-out athak5, atakt1 mutant show that AtHAK5 is the only system mediating K(+) uptake at concentrations below 0.01 mM. In the range between 0.01 and 0.05 mM K(+) AtHAK5 and AtAKT1 are the only contributors to K(+) acquisition. At higher K(+) concentrations, unknown systems come into operation and participate together with AtAKT1 in low-affinity K(+) uptake. These systems can supply sufficient K(+) to promote plant growth even in the absence of AtAKT1 or in the presence of 10 mM K(+) where AtAKT1 is not essential.
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Affiliation(s)
- Francisco Rubio
- Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura-CSIC, Campus de Espinardo, Murcia 30100, Spain.
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Hoopen FT, Cuin TA, Pedas P, Hegelund JN, Shabala S, Schjoerring JK, Jahn TP. Competition between uptake of ammonium and potassium in barley and Arabidopsis roots: molecular mechanisms and physiological consequences. JOURNAL OF EXPERIMENTAL BOTANY 2010; 61:2303-15. [PMID: 20339151 PMCID: PMC2877888 DOI: 10.1093/jxb/erq057] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Plants can use ammonium (NH4+) as the sole nitrogen source, but at high NH4+ concentrations in the root medium, particularly in combination with a low availability of K+, plants suffer from NH4+ toxicity. To understand the role of K+ transporters and non-selective cation channels in K+/NH4+ interactions better, growth, NH4+ and K+ accumulation and the specific fluxes of NH4+, K+, and H+ were examined in roots of barley (Hordeum vulgare L.) and Arabidopsis seedlings. Net fluxes of K+ and NH4+ were negatively correlated, as were their tissue concentrations, suggesting that there is direct competition during uptake. Pharmacological treatments with the K+ transport inhibitors tetraethyl ammonium (TEA+) and gadolinium (Gd3+) reduced NH4+ influx, and the addition of TEA+ alleviated the NH4+-induced depression of root growth in germinating Arabidopsis plants. Screening of a barley root cDNA library in a yeast mutant lacking all NH4+ and K+ uptake proteins through the deletion of MEP1-3 and TRK1 and TRK2 resulted in the cloning of the barley K+ transporter HvHKT2;1. Further analysis in yeast suggested that HvHKT2;1, AtAKT1, and AtHAK5 transported NH4+, and that K+ supplied at increasing concentrations competed with this NH4+ transport. On the other hand, uptake of K+ by AtHAK5, and to a lesser extent via HvHKT2;1 and AtAKT1, was inhibited by increasing concentrations of NH4+. Together, the results of this study show that plant K+ transporters and channels are able to transport NH4+. Unregulated NH4+ uptake via these transporters may contribute to NH4+ toxicity at low K+ levels, and may explain the alleviation of NH4+ toxicity by K+.
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Affiliation(s)
- Floor ten Hoopen
- Department of Agriculture and Ecology, Plant and Soil Science Laboratory, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
| | - Tracey Ann Cuin
- School of Agricultural Sciences, University of Tasmania, Private Bag 54, Hobart, Tasmania 7001
| | - Pai Pedas
- Department of Agriculture and Ecology, Plant and Soil Science Laboratory, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
| | - Josefine N. Hegelund
- Department of Agriculture and Ecology, Plant and Soil Science Laboratory, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
| | - Sergey Shabala
- School of Agricultural Sciences, University of Tasmania, Private Bag 54, Hobart, Tasmania 7001
| | - Jan K. Schjoerring
- Department of Agriculture and Ecology, Plant and Soil Science Laboratory, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
| | - Thomas P. Jahn
- Department of Agriculture and Ecology, Plant and Soil Science Laboratory, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
- To whom correspondence should be addressed: E-mail:
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Nieves-Cordones M, Alemán F, Martínez V, Rubio F. The Arabidopsis thaliana HAK5 K+ transporter is required for plant growth and K+ acquisition from low K+ solutions under saline conditions. MOLECULAR PLANT 2010; 3:326-33. [PMID: 20028724 DOI: 10.1093/mp/ssp102] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
K(+) uptake in the high-affinity range of concentrations and its components have been widely studied. In Arabidposis thaliana, the AtHAK5 transporter and the AtAKT1 channel have been shown to be the main transport proteins involved in this process. Here, we study the role of these two systems under two important stress conditions: low K(+) supply or the presence of salinity. T-DNA insertion lines disrupting AtHAK5 and AtAKT1 are employed for long-term experiments that allow physiological characterization of the mutant lines. We found that AtHAK5 is required for K(+) absorption necessary to sustain plant growth at low K(+) in the absence as well as in the presence of salinity. Salinity greatly reduced AtHAK5 transcript levels and promoted AtAKT1-mediated K(+) efflux, resulting in an important impairment of K(+) nutrition. Although having a limited capacity, AtHAK5 plays a major role for K(+) acquisition from low K(+) concentrations in the presence of salinity.
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Affiliation(s)
- Manuel Nieves-Cordones
- Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura, CSIC, Campus de Espinardo, 30100 Murcia, Spain
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Ache P, Fromm J, Hedrich R. Potassium-dependent wood formation in poplar: seasonal aspects and environmental limitations. PLANT BIOLOGY (STUTTGART, GERMANY) 2010; 12:259-67. [PMID: 20398233 DOI: 10.1111/j.1438-8677.2009.00282.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Potassium availability and acquisition are pivotal for the generation of biomass and thus wood formation in growing poplar trees. Here, we focus on the role of potassium (K(+)) in wood production, transitions between dormancy and active growth, and limiting environmental conditions. Molecular mechanisms, such as expression and activity of K(+) transporters and channels controlling seasonal changes in wood formation, are discussed.
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Affiliation(s)
- P Ache
- Universität Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Würzburg, Germany.
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Luan S, Lan W, Chul Lee S. Potassium nutrition, sodium toxicity, and calcium signaling: connections through the CBL-CIPK network. CURRENT OPINION IN PLANT BIOLOGY 2009; 12:339-46. [PMID: 19501014 DOI: 10.1016/j.pbi.2009.05.003] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Revised: 05/05/2009] [Accepted: 05/06/2009] [Indexed: 05/02/2023]
Abstract
Plant roots take up numerous minerals from the soil. Some minerals (e.g., K(+)) are essential nutrients and others (e.g., Na(+)) are toxic for plant growth and development. In addition to the absolute level, the balance among the minerals is critical for their physiological functions. For instance, [K(+)]/[Na(+)] ratio and homeostasis often determine plant growth rate. Either low-K or high-Na in the soil represents a stress condition that severely affects plant life and agricultural production. Earlier observations indicated that higher soil Ca2(+) improve plants growth under low-K or high-Na condition, implying functional interaction among the three cations. Recent studies have begun to delineate the signaling mechanisms underlying such interactions. Either low-K(+) or high-Na(+) can trigger cellular Ca2(+) changes that lead to activation of complex signaling networks. One such network consists of Ca2(+) sensor proteins (e.g., CBLs) interacting with their target kinases (CIPKs). The CBL-CIPK signaling modules interact with and regulate the activity of a number of transporting proteins involved in the uptake and translocation of K(+) and Na(+), maintaining the "balance" of these cations in plants under stress conditions.
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Affiliation(s)
- Sheng Luan
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA
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Karley AJ, White PJ. Moving cationic minerals to edible tissues: potassium, magnesium, calcium. CURRENT OPINION IN PLANT BIOLOGY 2009; 12:291-8. [PMID: 19481494 DOI: 10.1016/j.pbi.2009.04.013] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2008] [Revised: 04/27/2009] [Accepted: 04/28/2009] [Indexed: 05/02/2023]
Abstract
The principal dietary source to humans of the essential cationic mineral elements potassium, magnesium and calcium is through edible plants. The accumulation of these elements in edible portions is the product of selective transport processes catalysing their short-distance and long-distance movement within a plant. In this article we review recent work describing the identification and characterisation of the molecular mechanisms catalysing the uptake and distribution of potassium, magnesium and calcium between organs, cell types and subcellular compartments. Although potassium and magnesium are redistributed effectively within the plant, calcium concentrations in phloem-fed tissues, such as fruits, seeds and tubers, are generally low. However, limitations to the redistribution of mineral elements within the plant, and its consequences for the biofortification of edible crops, can be overcome by appropriate mineral fertilisation and plant breeding strategies. The techniques of ionomics can help identify better genotypes.
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