1
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Li Q, Zhu W, Yan Z, Ni D, Chen Y, Wang M. Integrated metabolomics and transcriptomics analyses reveal aluminum-activated malate transporter CsALMT14 contributing to fluoride tolerance in F-hyperaccumulator Camellia sinensis. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2025; 292:117932. [PMID: 39978103 DOI: 10.1016/j.ecoenv.2025.117932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2024] [Revised: 01/24/2025] [Accepted: 02/17/2025] [Indexed: 02/22/2025]
Abstract
Tea plants (Camellia sinensis) tend to accumulate excessive amounts of fluoride (F) compared to other plants. However, the specific mechanisms of F tolerance or detoxification in tea plants remain insufficiently understood. This study employed ultra-high performance liquid chromatography quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF/MS) to identify critical metabolites involved in F detoxification across two distinct tea plant cultivars with varying F accumulation capacities. Notably, malic acid and citric acid emerged as key metabolites that differentially accumulated under F-stressed conditions. Weighted gene co-expression network analysis indicated that C. sinensis aluminum (Al)-activated malate transporter genes CsALMT9 and CsALMT14 may be implicated in the response to F stress in C. sinensis. Further investigations revealed that CsALMT14 localized to the plasma membrane and exhibited significant transcriptional induction upon exposure to F toxicity. Moreover, heterologous expression of CsALMT14 enhanced F tolerance by mitigating F accumulation in transgenic yeast and Arabidopsis thaliana. Additionally, silencing of CsALMT14 by antisense oligodeoxynucleotide and virus-induced gene silencing reduced the content of malic acid but increased the accumulation of citric acid in tea plants, which might be attributed to the down-regulated expression of malic acid synthesis- and citric acid degradation-related genes. These findings suggest that CsALMT14 confers tolerance to F toxicity through F efflux and regulation of malic acid and citric acid metabolism-related gene expression, thereby providing a novel strategy for F detoxification in tea plants.
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Affiliation(s)
- Qinghui Li
- National Key Laboratory for Germplasm Innovation and Utilization of Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, PR China.
| | - Wenrui Zhu
- National Key Laboratory for Germplasm Innovation and Utilization of Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, PR China.
| | - Zhihao Yan
- National Key Laboratory for Germplasm Innovation and Utilization of Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, PR China.
| | - Dejiang Ni
- National Key Laboratory for Germplasm Innovation and Utilization of Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, PR China.
| | - Yuqiong Chen
- National Key Laboratory for Germplasm Innovation and Utilization of Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, PR China.
| | - Mingle Wang
- National Key Laboratory for Germplasm Innovation and Utilization of Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, PR China.
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2
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Qian D, Chai Y, Li W, Cui B, Lin S, Wang Z, Wang C, Qu LQ, Gong D. Structural insight into the Arabidopsis vacuolar anion channel ALMT9 shows clade specificity. Cell Rep 2024; 43:114731. [PMID: 39269901 DOI: 10.1016/j.celrep.2024.114731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Revised: 06/26/2024] [Accepted: 08/23/2024] [Indexed: 09/15/2024] Open
Abstract
The Arabidopsis thaliana aluminum-activated malate transporter 9 (AtALMT9) functions as a vacuolar chloride channel that regulates the stomatal aperture. Here, we present the cryoelectron microscopy (cryo-EM) structures of AtALMT9 in three distinct states. AtALMT9 forms a dimer, and the pore is lined with four positively charged rings. The apo-AtALMT9 state shows a putative endogenous citrate obstructing the pore, where two W120 constriction residues enclose a gate with a pore radius of approximately 1.8 Å, representing an open state. Interestingly, channel closure is solely controlled by W120. Compared to wild-type plants, the W120A mutant exhibits more sensitivity to drought stress and is unable to restore the visual phenotype on leaves upon water recovery, reflecting persistent stomatal opening. Furthermore, notable variations are noted in channel gating and substrate recognition of Glycine max ALMT12, AtALMT9, and AtALMT1. In summary, our investigation enhances comprehension of the interplay between structure and function within the ALMT family.
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Affiliation(s)
- Dandan Qian
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, Tianjin 300350, China.
| | - Yaru Chai
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing 100093, China; College of Life Science, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Weiping Li
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, Tianjin 300350, China
| | - Bin Cui
- School of Basic Medicine and Clinical Pharmacy and State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing 210009, China
| | - Shaoquan Lin
- Faculty of Pharmaceutical Sciences, Shenzhen University of Advanced Technology, Shenzhen 581055, China
| | - Zhibin Wang
- Faculty of Pharmaceutical Sciences, Shenzhen University of Advanced Technology, Shenzhen 581055, China
| | - Chongyuan Wang
- Faculty of Pharmaceutical Sciences, Shenzhen University of Advanced Technology, Shenzhen 581055, China.
| | - Le Qing Qu
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing 100093, China; College of Life Science, University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Deshun Gong
- State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, Tianjin 300350, China.
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3
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Peng FC, Yuan M, Zhou L, Zheng BQ, Wang Y. Identification and Analysis of Aluminum-Activated Malate Transporter Gene Family Reveals Functional Diversification in Orchidaceae and the Expression Patterns of Dendrobium catenatum Aluminum-Activated Malate Transporters. Int J Mol Sci 2024; 25:9662. [PMID: 39273609 PMCID: PMC11394931 DOI: 10.3390/ijms25179662] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2024] [Revised: 08/30/2024] [Accepted: 09/03/2024] [Indexed: 09/15/2024] Open
Abstract
Aluminum-activated malate transporter (ALMT) genes play an important role in aluminum ion (Al3+) tolerance, fruit acidity, and stomatal movement. Although decades of research have been carried out in many plants, there is little knowledge about the roles of ALMT in Orchidaceae. In this study, 34 ALMT genes were identified in the genomes of four orchid species. Specifically, ten ALMT genes were found in Dendrobium chrysotoxum and D. catenatum, and seven were found in Apostasia shenzhenica and Phalaenopsis equestris. These ALMT genes were further categorized into four clades (clades 1-4) based on phylogenetic relationships. Sequence alignment and conserved motif analysis revealed that most orchid ALMT proteins contain conserved regions (TM1, GABA binding motif, and WEP motif). We also discovered a unique motif (19) belonging to clade 1, which can serve as a specifically identified characteristic. Comparison with the gene structure of AtALMT genes (Arabidopsis thaliana) showed that the gene structure of ALMT was conserved across species, but the introns were longer in orchids. The promoters of orchid ALMT genes contain many light-responsive and hormone-responsive elements, suggesting that their expression may be regulated by light and phytohormones. Chromosomal localization and collinear analysis of D. chrysotoxum indicated that tandem duplication (TD) is the main reason for the difference in the number of ALMT genes in these orchids. D. catenatum was chosen for the RT-qPCR experiment, and the results showed that the DcaALMT gene expression pattern varied in different tissues. The expression of DcaALMT1-9 was significantly changed after ABA treatment. Combining the circadian CO2 uptake rate, titratable total acid, and RT-qPCR data analysis, most DcaALMT genes were highly expressed at night and around dawn. The result revealed that DcaALMT genes might be involved in photosynthate accumulation. The above study provides more comprehensive information for the ALMT gene family in Orchidaceae and a basis for subsequent functional analysis.
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Affiliation(s)
| | | | | | | | - Yan Wang
- Key Laboratory of Tree Breeding and Cultivation of National Forestry and Grassland Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing 100091, China; (F.-C.P.); (M.Y.); (L.Z.); (B.-Q.Z.)
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4
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Dabravolski SA, Isayenkov SV. Recent Updates on ALMT Transporters' Physiology, Regulation, and Molecular Evolution in Plants. PLANTS (BASEL, SWITZERLAND) 2023; 12:3167. [PMID: 37687416 PMCID: PMC10490231 DOI: 10.3390/plants12173167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 08/18/2023] [Accepted: 08/29/2023] [Indexed: 09/10/2023]
Abstract
Aluminium toxicity and phosphorus deficiency in soils are the main interconnected problems of modern agriculture. The aluminium-activated malate transporters (ALMTs) comprise a membrane protein family that demonstrates various physiological functions in plants, such as tolerance to environmental Al3+ and the regulation of stomatal movement. Over the past few decades, the regulation of ALMT family proteins has been intensively studied. In this review, we summarise the current knowledge about this transporter family and assess their involvement in diverse physiological processes and comprehensive regulatory mechanisms. Furthermore, we have conducted a thorough bioinformatic analysis to decipher the functional importance of conserved residues, structural components, and domains. Our phylogenetic analysis has also provided new insights into the molecular evolution of ALMT family proteins, expanding their scope beyond the plant kingdom. Lastly, we have formulated several outstanding questions and research directions to further enhance our understanding of the fundamental role of ALMT proteins and to assess their physiological functions.
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Affiliation(s)
- Siarhei A. Dabravolski
- Department of Biotechnology Engineering, Braude Academic College of Engineering, Snunit 51, Karmiel 2161002, Israel;
| | - Stanislav V. Isayenkov
- Institute of Agricultural and Nutritional Sciences, Martin Luther University Halle-Wittenberg, Betty-Heimann-Strasse 3, 06120 Halle, Germany
- Department of Plant Food Products and Biofortification, Institute of Food Biotechnology and Genomics, The National Academy of Sciences of Ukraine, Osipovskogo Str. 2a, 04123 Kyiv, Ukraine
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Jaślan J, Marten I, Jakobson L, Arjus T, Deeken R, Sarmiento C, De Angeli A, Brosché M, Kollist H, Hedrich R. ALMT-independent guard cell R-type anion currents. THE NEW PHYTOLOGIST 2023; 239:2225-2234. [PMID: 37434346 DOI: 10.1111/nph.19124] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Accepted: 06/12/2023] [Indexed: 07/13/2023]
Abstract
Plant transpiration is controlled by stomata, with S- and R-type anion channels playing key roles in guard cell action. Arabidopsis mutants lacking the ALMT12/QUAC1 R-type anion channel function in guard cells show only a partial reduction in R-type channel currents. The molecular nature of these remaining R-type anion currents is still unclear. To further elucidate this, patch clamp, transcript and gas-exchange measurements were performed with wild-type (WT) and different almt mutant plants. The R-type current fraction in the almt12 mutant exhibited the same voltage dependence, susceptibility to ATP block and lacked a chloride permeability as the WT. Therefore, we asked whether the R-type anion currents in the ALMT12/QUAC1-free mutant are caused by additional ALMT isoforms. In WT guard cells, ALMT12, ALMT13 and ALMT14 transcripts were detected, whereas only ALMT13 was found expressed in the almt12 mutant. Substantial R-type anion currents still remained active in the almt12/13 and almt12/14 double mutants as well as the almt12/13/14 triple mutant. In good agreement, CO2 -triggered stomatal closure required the activity of ALMT12 but not ALMT13 or ALMT14. The results suggest that, with the exception of ALMT12, channel species other than ALMTs carry the guard cell R-type anion currents.
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Affiliation(s)
- Justyna Jaślan
- Department of Molecular Plant Physiology and Biophysics, Biocenter, Julius-Maximilians-Universität Würzburg (JMU), Würzburg, D-97082, Germany
- IPSiM, Univ Montpellier, CNRS, INRAE, Institut Agro, Montpellier, 34060, France
| | - Irene Marten
- Department of Molecular Plant Physiology and Biophysics, Biocenter, Julius-Maximilians-Universität Würzburg (JMU), Würzburg, D-97082, Germany
| | - Liina Jakobson
- Plant Signal Research Group, Institute of Technology, University of Tartu, Tartu, 50411, Estonia
- Estonian Crop Research Institute, J. Aamisepa 1, Jõgeva, 48309, Estonia
| | - Triinu Arjus
- Plant Signal Research Group, Institute of Technology, University of Tartu, Tartu, 50411, Estonia
| | - Rosalia Deeken
- Department of Molecular Plant Physiology and Biophysics, Biocenter, Julius-Maximilians-Universität Würzburg (JMU), Würzburg, D-97082, Germany
| | - Cecilia Sarmiento
- Department of Chemistry and Biotechnology, Tallinn University of Technology, Tallinn, 12618, Estonia
| | - Alexis De Angeli
- IPSiM, Univ Montpellier, CNRS, INRAE, Institut Agro, Montpellier, 34060, France
| | - Mikael Brosché
- Organismal and Evolutionary Biology Research Program, Faculty of Biological and Environmental Sciences, Viikki Plant Science Centre, University of Helsinki, Helsinki, 00790, Finland
| | - Hannes Kollist
- Plant Signal Research Group, Institute of Technology, University of Tartu, Tartu, 50411, Estonia
| | - Rainer Hedrich
- Department of Molecular Plant Physiology and Biophysics, Biocenter, Julius-Maximilians-Universität Würzburg (JMU), Würzburg, D-97082, Germany
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6
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Fromm J, Lautner S. Electrical Signaling and Its Functions Under Conditions of Abiotic Stress: A Review of Methodological Approaches and Physiological Implications. Methods Mol Biol 2023; 2642:179-193. [PMID: 36944879 DOI: 10.1007/978-1-0716-3044-0_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2023]
Abstract
In contrast to chemical messengers, electrical signals such as action potentials and variation potentials can transmit information much faster over long distances. Electrical signals can be triggered by various abiotic stress factors and are propagated via plasmodesmata over short distances and within the phloem over long distances. Thus, in addition to assimilate transport from sources to sinks, the phloem serves as a communication highway for various types of information. Key factors for systemic signaling in the phloem are peptides, RNAs, hormones, and electrical signals. In recent years, there has been increasing evidence that rapid communication by means of electrical signals is essential for various plant physiological processes. Thus, this chapter focuses on electrical signaling and various associated physiological effects, such as regulation of leaf movements, assimilate transport, photosynthesis, and gas exchange, as well as plant water status.
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Affiliation(s)
- Jörg Fromm
- Wood Biology, Institute for Wood Science, Universität Hamburg, Hamburg, Germany.
| | - Silke Lautner
- Applied Wood Biology, Eberswalde University for Sustainable Development, Eberswalde, Germany
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7
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Zhou H, Hu Z, Luo Y, Feng C, Long Y. Multiple ALMT subunits combine to form functional anion channels: A case study for rice ALMT7. FRONTIERS IN PLANT SCIENCE 2022; 13:1012578. [PMID: 36452104 PMCID: PMC9702572 DOI: 10.3389/fpls.2022.1012578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Accepted: 10/03/2022] [Indexed: 06/17/2023]
Abstract
The Aluminum Activated Malate Transporter (ALMT) family members are anion channels that play important roles in organic acid transport, stress resistance, growth, development, fertilization and GABA responses. The rice malate permeable OsALMT7 influences panicle development and grain yield. A truncated OsALMT7 mutant, panicle apical abortion1 (paab1) lacking at least 2 transmembrane helices, mediates reduced malate efflux resulting in yield reducing. Here, we further investigated the contribution of OsALMT7 transmembrane helices to channel activity, using heterologous expression in Xenopus laevis oocytes. We further found that OsALMT7 formed as a homomer by co-expressing OsALMT7 and paab1 proteins in oocytes and detecting the physical interaction between two OsALMT7, and between OsALMT7 and paab1 mutant protein. Further study proved that not just OsALMT7, mutants of TaALMT1 inhibit wild-type TaALMT1 channel, indicating that ALMTs might perform channel function as homomers. Our discovery brings a light for ion channel structure and homomultimer regulation understanding for ALMT anion channels and potential for crop grain yield and stress response improvement in the context of the essential role of ALMTs in these plant processes.
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Affiliation(s)
| | | | | | | | - Yu Long
- *Correspondence: Yu Long, ; Cuizhu Feng,
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8
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Gilliham M, Xu B. γ-Aminobutyric acid may directly or indirectly regulate Arabidopsis ALMT9. PLANT PHYSIOLOGY 2022; 190:1570-1573. [PMID: 36047833 PMCID: PMC9614470 DOI: 10.1093/plphys/kiac399] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 07/19/2022] [Indexed: 06/15/2023]
Abstract
The mechanism by which GABA regulates stomatal pore aperture and anion transport activity of ALUMINUM-ACTIVATED MALATE TRANSPORTER 9 is debated.
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Affiliation(s)
| | - Bo Xu
- Authors for correspondence: (M.G.), (B.X.)
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9
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Brownlee C. Plant physiology: Anatomy of a plant action potential. Curr Biol 2022; 32:R1000-R1002. [PMID: 36220083 DOI: 10.1016/j.cub.2022.08.024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The Venus flytrap possesses modified leaves that can snap shut fast enough to catch a fly. A new study identifies the major components of the toolkit that allows the flytrap to fire action potentials, illustrating how different ion channels and transporters are recruited to give rise to this unique plant behavioural response.
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Affiliation(s)
- Colin Brownlee
- Marine Biological Association, the Laboratory, Citadel Hill, Plymouth, UK.
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10
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Scherzer S, Böhm J, Huang S, Iosip AL, Kreuzer I, Becker D, Heckmann M, Al-Rasheid KAS, Dreyer I, Hedrich R. A unique inventory of ion transporters poises the Venus flytrap to fast-propagating action potentials and calcium waves. Curr Biol 2022; 32:4255-4263.e5. [PMID: 36087579 DOI: 10.1016/j.cub.2022.08.051] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 06/20/2022] [Accepted: 08/17/2022] [Indexed: 12/14/2022]
Abstract
Since the 19th century, it has been known that the carnivorous Venus flytrap is electrically excitable. Nevertheless, the mechanism and the molecular entities of the flytrap action potential (AP) remain unknown. When entering the electrically excitable stage, the trap expressed a characteristic inventory of ion transporters, among which the increase in glutamate receptor GLR3.6 RNA was most pronounced. Trigger hair stimulation or glutamate application evoked an AP and a cytoplasmic Ca2+ transient that both propagated at the same speed from the site of induction along the entire trap lobe surface. A priming Ca2+ moiety entering the cytoplasm in the context of the AP was further potentiated by an organelle-localized calcium-induced calcium release (CICR)-like system prolonging the Ca2+ signal. While the Ca2+ transient persisted, SKOR K+ channels and AHA H+-ATPases repolarized the AP already. By counting the number of APs and long-lasting Ca2+ transients, the trap directs the different steps in the carnivorous plant's hunting cycle. VIDEO ABSTRACT.
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Affiliation(s)
- Sönke Scherzer
- Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Wuerzburg University, Julius-von-Sachs-Platz 2, 97070 Wuerzburg, Germany.
| | - Jennifer Böhm
- Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Wuerzburg University, Julius-von-Sachs-Platz 2, 97070 Wuerzburg, Germany
| | - Shouguang Huang
- Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Wuerzburg University, Julius-von-Sachs-Platz 2, 97070 Wuerzburg, Germany
| | - Anda L Iosip
- Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Wuerzburg University, Julius-von-Sachs-Platz 2, 97070 Wuerzburg, Germany
| | - Ines Kreuzer
- Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Wuerzburg University, Julius-von-Sachs-Platz 2, 97070 Wuerzburg, Germany
| | - Dirk Becker
- Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Wuerzburg University, Julius-von-Sachs-Platz 2, 97070 Wuerzburg, Germany
| | - Manfred Heckmann
- Department of Neurophysiology, Institute of Physiology, Wuerzburg University, Röntgenring 9, 97070 Wuerzburg, Germany
| | - Khaled A S Al-Rasheid
- Zoology Department, College of Science, King Saud University, Riyadh 11451, Saudi Arabia
| | - Ingo Dreyer
- Center of Bioinformatics, Simulation and Modeling (CBSM), Faculty of Engineering, Universidad de Talca, 2 Norte 685, Talca 3460000, Chile
| | - Rainer Hedrich
- Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Wuerzburg University, Julius-von-Sachs-Platz 2, 97070 Wuerzburg, Germany.
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11
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Sasaki T, Ariyoshi M, Yamamoto Y, Mori IC. Functional roles of ALMT-type anion channels in malate-induced stomatal closure in tomato and Arabidopsis. PLANT, CELL & ENVIRONMENT 2022; 45:2337-2350. [PMID: 35672880 DOI: 10.1111/pce.14373] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 04/21/2022] [Accepted: 05/29/2022] [Indexed: 06/15/2023]
Abstract
Guard-cell-type aluminium-activated malate transporters (ALMTs) are involved in stomatal closure by exporting anions from guard cells. However, their physiological and electrophysiological functions are yet to be explored. Here, we analysed the physiological and electrophysiological properties of the ALMT channels in Arabidopsis and tomato (Solanum lycopersicum). SlALMT11 was specifically expressed in tomato guard cells. External malate-induced stomatal closure was impaired in ALMT-suppressed lines of tomato and Arabidopsis, although abscisic acid did not influence the stomatal response in SlALMT11-knock-down tomato lines. Electrophysiological analyses in Xenopus oocytes showed that SlALMT11 and AtALMT12/QUAC1 exhibited characteristic bell-shaped current-voltage patterns dependent on extracellular malate, fumarate, and citrate. Both ALMTs could transport malate, fumarate, and succinate, but not citrate, suggesting that the guard-cell-type ALMTs are dicarboxylic anion channels activated by extracellular organic acids. The truncation of acidic amino acids, Asp or Glu, from the C-terminal end of SlALMT11 or AtALMT12/QUAC1 led to the disappearance of the bell-shaped current-voltage patterns. Our findings establish that malate-activated stomatal closure is mediated by guard-cell-type ALMT channels that require an acidic amino acid in the C-terminus as a candidate voltage sensor in both tomato and Arabidopsis.
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Affiliation(s)
- Takayuki Sasaki
- Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama, Japan
| | - Michiyo Ariyoshi
- Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama, Japan
| | - Yoko Yamamoto
- Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama, Japan
| | - Izumi C Mori
- Institute of Plant Science and Resources, Okayama University, Kurashiki, Okayama, Japan
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12
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Qin L, Tang LH, Xu JS, Zhang XH, Zhu Y, Zhang CR, Wang MH, Liu XL, Li F, Sun F, Su M, Zhai Y, Chen YH. Cryo-EM structure and electrophysiological characterization of ALMT from Glycine max reveal a previously uncharacterized class of anion channels. SCIENCE ADVANCES 2022; 8:eabm3238. [PMID: 35235352 PMCID: PMC8890709 DOI: 10.1126/sciadv.abm3238] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 01/07/2022] [Indexed: 06/14/2023]
Abstract
Aluminum-activated malate transporters (ALMTs) form an anion channel family that plays essential roles in diverse functions in plants. Arabidopsis ALMT12, also named QUAC1 (quick anion channel 1), regulates stomatal closure in response to environmental stimuli. However, the molecular basis of ALMT12/QUAC1 activity remains elusive. Here, we describe the cryo-EM structure of ALMT12/QUAC1 from Glycine max at 3.5-Å resolution. GmALMT12/QUAC1 is a symmetrical dimer, forming a single electropositive T-shaped pore across the membrane. The transmembrane and cytoplasmic domains are assembled into a twisted two-layer architecture, with their associated dimeric interfaces nearly perpendicular. GmALMT12/QUAC1-mediated currents display rapid kinetics of activation/deactivation and a bell-shaped voltage dependency, reminiscent of the rapid (R)-type anion currents. Our structural and functional analyses reveal a domain-twisting mechanism for malate-mediated activation. Together, our study uncovers the molecular basis for a previously uncharacterized class of anion channels and provides insights into the gating and modulation of the ALMT12/QUAC1 anion channel.
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Affiliation(s)
- Li Qin
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing 100101, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ling-hui Tang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing 100101, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jia-shu Xu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- School of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xian-hui Zhang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing 100101, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yun Zhu
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- School of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chun-rui Zhang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing 100101, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Mei-hua Wang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing 100101, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xue-lei Liu
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing 100101, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Fei Li
- Department of Biology, New York University, New York, NY 10003, USA
| | - Fei Sun
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- School of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Min Su
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing 100101, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yujia Zhai
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- School of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yu-hang Chen
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing 100101, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
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13
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Scherzer S, Huang S, Iosip A, Kreuzer I, Yokawa K, Al-Rasheid KAS, Heckmann M, Hedrich R. Ether anesthetics prevents touch-induced trigger hair calcium-electrical signals excite the Venus flytrap. Sci Rep 2022; 12:2851. [PMID: 35181728 PMCID: PMC8857258 DOI: 10.1038/s41598-022-06915-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Accepted: 02/08/2022] [Indexed: 11/08/2022] Open
Abstract
Plants do not have neurons but operate transmembrane ion channels and can get electrical excited by physical and chemical clues. Among them the Venus flytrap is characterized by its peculiar hapto-electric signaling. When insects collide with trigger hairs emerging the trap inner surface, the mechanical stimulus within the mechanosensory organ is translated into a calcium signal and an action potential (AP). Here we asked how the Ca2+ wave and AP is initiated in the trigger hair and how it is feed into systemic trap calcium-electrical networks. When Dionaea muscipula trigger hairs matures and develop hapto-electric excitability the mechanosensitive anion channel DmMSL10/FLYC1 and voltage dependent SKOR type Shaker K+ channel are expressed in the sheering stress sensitive podium. The podium of the trigger hair is interface to the flytrap's prey capture and processing networks. In the excitable state touch stimulation of the trigger hair evokes a rise in the podium Ca2+ first and before the calcium signal together with an action potential travel all over the trap surface. In search for podium ion channels and pumps mediating touch induced Ca2+ transients, we, in mature trigger hairs firing fast Ca2+ signals and APs, found OSCA1.7 and GLR3.6 type Ca2+ channels and ACA2/10 Ca2+ pumps specifically expressed in the podium. Like trigger hair stimulation, glutamate application to the trap directly evoked a propagating Ca2+ and electrical event. Given that anesthetics affect K+ channels and glutamate receptors in the animal system we exposed flytraps to an ether atmosphere. As result propagation of touch and glutamate induced Ca2+ and AP long-distance signaling got suppressed, while the trap completely recovered excitability when ether was replaced by fresh air. In line with ether targeting a calcium channel addressing a Ca2+ activated anion channel the AP amplitude declined before the electrical signal ceased completely. Ether in the mechanosensory organ did neither prevent the touch induction of a calcium signal nor this post stimulus decay. This finding indicates that ether prevents the touch activated, glr3.6 expressing base of the trigger hair to excite the capture organ.
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Affiliation(s)
- Sönke Scherzer
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Platz 2, 97082, Würzburg, Germany.
| | - Shouguang Huang
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Platz 2, 97082, Würzburg, Germany
| | - Anda Iosip
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Platz 2, 97082, Würzburg, Germany
| | - Ines Kreuzer
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Platz 2, 97082, Würzburg, Germany
| | - Ken Yokawa
- School of Earth, Energy and Environmental Engineering, Faculty of Engineering, Kitami Institute of Technology, Hokkaido, 090-8507, Japan
| | - Khaled A S Al-Rasheid
- Zoology Department, College of Science, King Saud University, P.O. Box 2455, Riyadh, 11451, Saudi Arabia
| | - Manfred Heckmann
- Department of Neurophysiology, Institute of Physiology, University of Würzburg, Röntgenring 9, 97082, Würzburg, Germany
| | - Rainer Hedrich
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Platz 2, 97082, Würzburg, Germany.
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14
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Kashtoh H, Baek KH. Structural and Functional Insights into the Role of Guard Cell Ion Channels in Abiotic Stress-Induced Stomatal Closure. PLANTS (BASEL, SWITZERLAND) 2021; 10:plants10122774. [PMID: 34961246 PMCID: PMC8707303 DOI: 10.3390/plants10122774] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2021] [Revised: 11/25/2021] [Accepted: 12/07/2021] [Indexed: 06/14/2023]
Abstract
A stomatal pore is formed by a pair of specialized guard cells and serves as a major gateway for water transpiration and atmospheric CO2 influx for photosynthesis in plants. These pores must be tightly controlled, as inadequate CO2 intake and excessive water loss are devastating for plants. When the plants are exposed to extreme weather conditions such as high CO2 levels, O3, low air humidity, and drought, the turgor pressure of the guard cells exhibits an appropriate response against these stresses, which leads to stomatal closure. This phenomenon involves a complex network of ion channels and their regulation. It is well-established that the turgor pressure of guard cells is regulated by ions transportation across the membrane, such as anions and potassium ions. In this review, the guard cell ion channels are discussed, highlighting the structure and functions of key ion channels; the SLAC1 anion channel and KAT1 potassium channel, and their regulatory components, emphasizing their significance in guard cell response to various stimuli.
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15
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Huang XY, Wang CK, Zhao YW, Sun CH, Hu DG. Mechanisms and regulation of organic acid accumulation in plant vacuoles. HORTICULTURE RESEARCH 2021; 8:227. [PMID: 34697291 PMCID: PMC8546024 DOI: 10.1038/s41438-021-00702-z] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 09/09/2021] [Accepted: 09/24/2021] [Indexed: 06/13/2023]
Abstract
In fleshy fruits, organic acids are the main source of fruit acidity and play an important role in regulating osmotic pressure, pH homeostasis, stress resistance, and fruit quality. The transport of organic acids from the cytosol to the vacuole and their storage are complex processes. A large number of transporters carry organic acids from the cytosol to the vacuole with the assistance of various proton pumps and enzymes. However, much remains to be explored regarding the vacuolar transport mechanism of organic acids as well as the substances involved and their association. In this review, recent advances in the vacuolar transport mechanism of organic acids in plants are summarized from the perspectives of transporters, channels, proton pumps, and upstream regulators to better understand the complex regulatory networks involved in fruit acid formation.
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Affiliation(s)
- Xiao-Yu Huang
- National Key Laboratory of Crop Biology; Shandong Collaborative Innovation Center of Fruit & Vegetable Quality and Efficient Production; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an, Shandong, 271018, China
| | - Chu-Kun Wang
- National Key Laboratory of Crop Biology; Shandong Collaborative Innovation Center of Fruit & Vegetable Quality and Efficient Production; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an, Shandong, 271018, China
| | - Yu-Wen Zhao
- National Key Laboratory of Crop Biology; Shandong Collaborative Innovation Center of Fruit & Vegetable Quality and Efficient Production; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an, Shandong, 271018, China
| | - Cui-Hui Sun
- National Key Laboratory of Crop Biology; Shandong Collaborative Innovation Center of Fruit & Vegetable Quality and Efficient Production; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an, Shandong, 271018, China.
| | - Da-Gang Hu
- National Key Laboratory of Crop Biology; Shandong Collaborative Innovation Center of Fruit & Vegetable Quality and Efficient Production; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an, Shandong, 271018, China.
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16
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Lefoulon C, Boxall SF, Hartwell J, Blatt MR. Crassulacean acid metabolism guard cell anion channel activity follows transcript abundance and is suppressed by apoplastic malate. THE NEW PHYTOLOGIST 2020; 227:1847-1857. [PMID: 32367511 DOI: 10.1111/nph.16640] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Accepted: 04/22/2020] [Indexed: 06/11/2023]
Abstract
Plants utilising crassulacean acid metabolism (CAM) concentrate CO2 around RuBisCO while reducing transpirational water loss associated with photosynthesis. Unlike stomata of C3 and C4 species, CAM stomata open at night for the mesophyll to fix CO2 into malate (Mal) and store it in the vacuole. CAM plants decarboxylate Mal in the light, generating high CO2 concentrations within the leaf behind closed stomata for refixation by RuBisCO. CO2 may contribute to stomatal closure but additional mechanisms, plausibly including Mal activation of anion channels, ensure closure in the light. In the CAM species Kalanchoë fedtschenkoi, we found that guard cell anion channel activity, recorded under voltage clamp, follows KfSLAC1 and KfALMT12 transcript abundance, declining to near zero by the end of the light period. Unexpectedly, however, we found that extracellular Mal inhibited the anion current of Kalanchoë guard cells, both in wild-type and RNAi mutants with impaired Mal metabolism. We conclude that the diurnal cycle of anion channel gene transcription, rather than the physiological signal of Mal release, is a key factor in the inverted CAM stomatal cycle.
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Affiliation(s)
- Cécile Lefoulon
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Bower Building, Glasgow, G12 8QQ, UK
| | - Susanna F Boxall
- Department of Functional and Comparative Genomics, Institute of Integrative Biology, University of Liverpool, Biosciences Building, Crown Street, Liverpool,, L69 7ZB, UK
| | - James Hartwell
- Department of Functional and Comparative Genomics, Institute of Integrative Biology, University of Liverpool, Biosciences Building, Crown Street, Liverpool,, L69 7ZB, UK
| | - Michael R Blatt
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Bower Building, Glasgow, G12 8QQ, UK
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17
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Engineering energetically efficient transport of dicarboxylic acids in yeast Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 2019; 116:19415-19420. [PMID: 31467169 PMCID: PMC6765260 DOI: 10.1073/pnas.1900287116] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The export of organic acids is typically proton or sodium coupled and requires energetic expenditure. Consequently, the cell factories producing organic acids must use part of the carbon feedstock on generating the energy for export, which decreases the overall process yield. Here, we show that organic acids can be exported from yeast cells by voltage-gated anion channels without the use of proton, sodium, or ATP motive force, resulting in more efficient fermentation processes. Biobased C4-dicarboxylic acids are attractive sustainable precursors for polymers and other materials. Commercial scale production of these acids at high titers requires efficient secretion by cell factories. In this study, we characterized 7 dicarboxylic acid transporters in Xenopus oocytes and in Saccharomyces cerevisiae engineered for dicarboxylic acid production. Among the tested transporters, the Mae1(p) from Schizosaccharomyces pombe had the highest activity toward succinic, malic, and fumaric acids and resulted in 3-, 8-, and 5-fold titer increases, respectively, in S. cerevisiae, while not affecting growth, which was in contrast to the tested transporters from the tellurite-resistance/dicarboxylate transporter (TDT) family or the Na+ coupled divalent anion–sodium symporter family. Similar to SpMae1(p), its homolog in Aspergillus carbonarius, AcDct(p), increased the malate titer 12-fold without affecting the growth. Phylogenetic and protein motif analyses mapped SpMae1(p) and AcDct(p) into the voltage-dependent slow-anion channel transporter (SLAC1) clade of transporters, which also include plant Slac1(p) transporters involved in stomata closure. The conserved phenylalanine residue F329 closing the transport pore of SpMae1(p) is essential for the transporter activity. The voltage-dependent SLAC1 transporters do not use proton or Na+ motive force and are, thus, less energetically expensive than the majority of other dicarboxylic acid transporters. Such transporters present a tremendous advantage for organic acid production via fermentation allowing a higher overall product yield.
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18
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Wang L, Guo MY, Thibaud JB, Véry AA, Sentenac H. A repertoire of cationic and anionic conductances at the plasma membrane of Medicago truncatula root hairs. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2019; 98:418-433. [PMID: 30673148 DOI: 10.1111/tpj.14238] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 12/22/2018] [Accepted: 01/18/2019] [Indexed: 05/15/2023]
Abstract
Root hairs, as lateral extensions of epidermal cells, provide large absorptive surfaces to the root and are major actors in plant hydromineral nutrition. In contact with the soil they also constitute a site of interactions between the plant and rhizospheric microorganisms. In legumes, initiation of symbiotic interactions with N2 -fixing rhizobia is often triggered at the root hair cell membrane in response to nodulation factors secreted by rhizobia, and involves early signaling events with changes in H+ , Ca2+ , K+ and Cl- fluxes inducing transient depolarization of the cell membrane. Here, we aimed to build a functional repertoire of the major root hair conductances to cations and anions in the sequenced legume model Medicago truncatula. Five root hair conductances were characterized through patch-clamp experiments on enzymatically recovered root hair protoplasts. These conductances displayed varying properties of voltage dependence, kinetics and ion selectivity. They consisted of hyperpolarization- and depolarization-activated conductances for K+ , cations or Cl- . Among these, one weakly outwardly rectifying cationic conductance and one hyperpolarization-activated slowly inactivating anionic conductance were not known as active in root hairs. All five conductances were detected in apical regions of young growing root hairs using membrane spheroplasts obtained by laser-assisted cell-wall microdissection. Combined with recent root hair transcriptomes of M. truncatula, this functional repertoire of conductances is expected to help the identification of candidate genes for reverse genetics studies to investigate the possible role of each conductance in root hair growth and interaction with the biotic and abiotic environment.
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Affiliation(s)
- Limin Wang
- Biochimie et Physiologie Moléculaire des Plantes, UMR Univ. Montpellier, CNRS, INRA, SupAgro, 34060, Montpellier Cedex 2, France
| | - Man-Yuan Guo
- Biochimie et Physiologie Moléculaire des Plantes, UMR Univ. Montpellier, CNRS, INRA, SupAgro, 34060, Montpellier Cedex 2, France
| | - Jean-Baptiste Thibaud
- Biochimie et Physiologie Moléculaire des Plantes, UMR Univ. Montpellier, CNRS, INRA, SupAgro, 34060, Montpellier Cedex 2, France
- Institut des Biomolécules Max Mousseron, UMR 5247, CNRS-UM-ENSCM, Faculté de Pharmacie, 15 Avenue Charles Flahault, BP 14491, F34093, Montpellier, Cedex 5, France
| | - Anne-Aliénor Véry
- Biochimie et Physiologie Moléculaire des Plantes, UMR Univ. Montpellier, CNRS, INRA, SupAgro, 34060, Montpellier Cedex 2, France
| | - Hervé Sentenac
- Biochimie et Physiologie Moléculaire des Plantes, UMR Univ. Montpellier, CNRS, INRA, SupAgro, 34060, Montpellier Cedex 2, France
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19
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Luu K, Rajagopalan N, Ching JCH, Loewen MC, Loewen ME. The malate-activated ALMT12 anion channel in the grass Brachypodium distachyon is co-activated by Ca 2+/calmodulin. J Biol Chem 2019; 294:6142-6156. [PMID: 30770467 PMCID: PMC6463695 DOI: 10.1074/jbc.ra118.005301] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 02/12/2019] [Indexed: 01/09/2023] Open
Abstract
In plants, strict regulation of stomatal pores is critical for modulation of CO2 fixation and transpiration. Under certain abiotic and biotic stressors, pore closure is initiated through anionic flux, with calcium (Ca2+) playing a central role. The aluminum-activated malate transporter 12 (ALMT12) is a malate-activated, voltage-dependent member of the aluminum-activated malate transporter family that has been implicated in anionic flux from guard cells controlling the stomatal aperture. Herein, we report the characterization of the regulatory mechanisms mediating channel activities of an ALMT from the grass Brachypodium distachyon (BdALMT12) that has the highest sequence identity to Arabidopsis thaliana ALMT12. Electrophysiological studies in a heterologous cell system confirmed that this channel is malate- and voltage-dependent. However, this was shown to be true only in the presence of Ca2+ Although a general kinase inhibitor increased the current density of BdALMT12, a calmodulin (CaM) inhibitor reduced the Ca2+-dependent channel activation. We investigated the physiological relevance of the CaM-based regulation in planta, where stomatal closure, induced by exogenous Ca2+ ionophore and malate, was shown to be inhibited by exogenous application of a CaM inhibitor. Subsequent analyses revealed that the double substitutions R335A/R338A and R335A/K342A, within a predicted BdALMT12 CaM-binding domain (CBD), also decreased the channels' ability to activate. Using isothermal titration calorimetry and CBD-mimetic peptides, as well as CaM-agarose affinity pulldown of full-length recombinant BdALMT12, we confirmed the physical interaction between the CBD and CaM. Together, these findings support a co-regulatory mechanism of BdALMT12 activation by malate, and Ca2+/CaM, emphasizing that a complex regulatory network modulates BdALMT12 activity.
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Affiliation(s)
- Khanh Luu
- From the Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 1B8
| | | | - John C H Ching
- From the Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 1B8
| | - Michele C Loewen
- the National Research Council of Canada, Saskatoon, Saskatchewan S7N 0W9; the National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada; the Department of Biomedical and Molecular Sciences, Queens University, Kingston, Ontario K7L 0N6, Canada.
| | - Matthew E Loewen
- From the Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Saskatchewan S7N 1B8
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20
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Saito S, Uozumi N. Guard Cell Membrane Anion Transport Systems and Their Regulatory Components: An Elaborate Mechanism Controlling Stress-Induced Stomatal Closure. PLANTS 2019; 8:plants8010009. [PMID: 30609843 PMCID: PMC6359458 DOI: 10.3390/plants8010009] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 11/19/2018] [Accepted: 12/16/2018] [Indexed: 02/07/2023]
Abstract
When plants are exposed to drastic environmental changes such as drought, salt or bacterial invasion, rapid stomatal movement confers tolerance to these stresses. This process involves a variety of guard cell expressed ion channels and their complex regulation network. Inward K+ channels mainly function in stomatal opening. On the other hand, guard cell anion channels play a crucial role in the closing of stomata, which is vital in terms of preventing water loss and bacterial entrance. Massive progress has been made on the research of these anion channels in the last decade. In this review, we focus on the function and regulation of Arabidopsis guard cell anion channels. Starting from SLAC1, a main contributor of stomatal closure, members of SLAHs (SLAC1 homologues), AtNRTs (Nitrate transporters), AtALMTs (Aluminum-activated malate transporters), ABC transporters, AtCLCs (Chloride channels), DTXs (Detoxification efflux carriers), SULTRs (Sulfate transporters), and their regulator components are reviewed. These membrane transport systems are the keys to maintaining cellular ion homeostasis against fluctuating external circumstances.
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Affiliation(s)
- Shunya Saito
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai 980-8579, Japan.
| | - Nobuyuki Uozumi
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai 980-8579, Japan.
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21
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Gutermuth T, Herbell S, Lassig R, Brosché M, Romeis T, Feijó JA, Hedrich R, Konrad KR. Tip-localized Ca 2+ -permeable channels control pollen tube growth via kinase-dependent R- and S-type anion channel regulation. THE NEW PHYTOLOGIST 2018; 218:1089-1105. [PMID: 29522235 DOI: 10.1111/nph.15067] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Accepted: 01/18/2018] [Indexed: 05/26/2023]
Abstract
Pollen tubes (PTs) are characterized by having tip-focused cytosolic calcium ion (Ca2+ ) concentration ([Ca2+ ]cyt ) gradients, which are believed to control PT growth. However, the mechanisms by which the apical [Ca2+ ]cyt orchestrates PT growth are not well understood. Here, we aimed to identify these mechanisms by combining reverse genetics, cell biology, electrophysiology, and live-cell Ca2+ and anion imaging. We triggered Ca2+ -channel activation by applying hyperpolarizing voltage pulses and observed that the evoked [Ca2+ ]cyt increases were paralleled by high anion channel activity and a decrease in the cytosolic anion concentration at the PT tip. We confirmed a functional correlation between these patterns by showing that inhibition of Ca2+ -permeable channels eliminated the [Ca2+ ]cyt increase, resulting in the abrogation of anion channel activity via Ca2+ -dependent protein kinases (CPKs). Functional characterization of CPK and anion-channel mutants revealed a CPK2/20/6-dependent activation of SLAH3 and ALMT12/13/14 anion channels. The impaired growth phenotypes of anion channel and CPK mutants support the physiological significance of a kinase- and Ca2+ -dependent pathway to control PT growth via anion channel activation. Other than unveiling this functional link, our membrane hyperpolarization method allows for unprecedented manipulation of the [Ca2+ ]cyt gradient or oscillations in the PT tips and opens an array of opportunities for channel screenings.
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Affiliation(s)
- Timo Gutermuth
- Department of Botany I, Julius-Von-Sachs Institute for Biosciences, University of Wuerzburg, 97082, Wuerzburg, Germany
| | - Sarah Herbell
- Department of Botany I, Julius-Von-Sachs Institute for Biosciences, University of Wuerzburg, 97082, Wuerzburg, Germany
| | - Roman Lassig
- Plant Biochemistry, Dahlem Centre of Plant Sciences, FU Berlin, Königin-Luise-Straße 12/16, 14195, Berlin, Germany
| | - Mikael Brosché
- Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki, 00014, Helsinki, Finland
- Institute of Technology, University of Tartu, Nooruse 1, 50411, Tartu, Estonia
| | - Tina Romeis
- Plant Biochemistry, Dahlem Centre of Plant Sciences, FU Berlin, Königin-Luise-Straße 12/16, 14195, Berlin, Germany
| | - José Alberto Feijó
- Department of Cell Biology & Molecular Genetics, University of Maryland, 2136 Bioscience Research Building, College Park, MD, 20742-5815, USA
| | - Rainer Hedrich
- Department of Botany I, Julius-Von-Sachs Institute for Biosciences, University of Wuerzburg, 97082, Wuerzburg, Germany
| | - Kai Robert Konrad
- Department of Botany I, Julius-Von-Sachs Institute for Biosciences, University of Wuerzburg, 97082, Wuerzburg, Germany
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23
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Wang YG, Fu FL, Yu HQ, Hu T, Zhang YY, Tao Y, Zhu JK, Zhao Y, Li WC. Interaction network of core ABA signaling components in maize. PLANT MOLECULAR BIOLOGY 2018; 96:245-263. [PMID: 29344831 DOI: 10.1007/s11103-017-0692-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 12/06/2017] [Indexed: 05/08/2023]
Abstract
We defined a comprehensive core ABA signaling network in monocot maize, including the gene expression, subcellular localization and interaction network of ZmPYLs, ZmPP2Cs, ZmSnRK2s and the putative substrates. The phytohormone abscisic acid (ABA) plays an important role in plant developmental processes and abiotic stress responses. In Arabidopsis, ABA is sensed by the PYL ABA receptors, which leads to binding of the PP2C protein phosphatase and activation of the SnRK2 protein kinases. These components functioning diversely and redundantly in ABA signaling are little known in maize. Using Arabidopsis pyl112458 and snrk2.2/3/6 mutants, we identified several ABA-responsive ZmPYLs and ZmSnRK2s, and also ZmPP2Cs. We showed the gene expression, subcellular localization and interaction network of ZmPYLs, ZmPP2Cs, and ZmSnRK2s, and the isolation of putative ZmSnRK2 substrates by mass spectrometry in monocot maize. We found that the ABA dependency of PYL-PP2C interactions is contingent on the identity of the PP2Cs. Among 238 candidate substrates for ABA-activated protein kinases, 69 are putative ZmSnRK2 substrates. Besides homologs of previously reported putative AtSnRK2 substrates, 23 phosphoproteins have not been discovered in the dicot Arabidopsis. Thus, we have defined a comprehensive core ABA signaling network in monocot maize and shed new light on ABA signaling.
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Affiliation(s)
- Ying-Ge Wang
- Maize Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China
| | - Feng-Ling Fu
- Maize Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China
| | - Hao-Qiang Yu
- Maize Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China
| | - Tao Hu
- Shanghai Center for Plant Stress Biology, and CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, 200032, China
| | - Yuan-Yuan Zhang
- Maize Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China
| | - Yi Tao
- Maize Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China
| | - Jian-Kang Zhu
- Shanghai Center for Plant Stress Biology, and CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, 200032, China
| | - Yang Zhao
- Shanghai Center for Plant Stress Biology, and CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, 200032, China.
| | - Wan-Chen Li
- Maize Research Institute, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
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24
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Daloso DM, Medeiros DB, Dos Anjos L, Yoshida T, Araújo WL, Fernie AR. Metabolism within the specialized guard cells of plants. THE NEW PHYTOLOGIST 2017; 216:1018-1033. [PMID: 28984366 DOI: 10.1111/nph.14823] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 08/21/2017] [Indexed: 05/21/2023]
Abstract
Contents 1018 I. 1018 II. 1019 III. 1022 IV. 1025 V. 1026 VI. 1029 1030 References 1030 SUMMARY: Stomata are leaf epidermal structures consisting of two guard cells surrounding a pore. Changes in the aperture of this pore regulate plant water-use efficiency, defined as gain of C by photosynthesis per leaf water transpired. Stomatal aperture is actively regulated by reversible changes in guard cell osmolyte content. Despite the fact that guard cells can photosynthesize on their own, the accumulation of mesophyll-derived metabolites can seemingly act as signals which contribute to the regulation of stomatal movement. It has been shown that malate can act as a signalling molecule and a counter-ion of potassium, a well-established osmolyte that accumulates in the vacuole of guard cells during stomatal opening. By contrast, their efflux from guard cells is an important mechanism during stomatal closure. It has been hypothesized that the breakdown of starch, sucrose and lipids is an important mechanism during stomatal opening, which may be related to ATP production through glycolysis and mitochondrial metabolism, and/or accumulation of osmolytes such as sugars and malate. However, experimental evidence supporting this theory is lacking. Here we highlight the particularities of guard cell metabolism and discuss this in the context of the guard cells themselves and their interaction with the mesophyll cells.
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Affiliation(s)
- Danilo M Daloso
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, Fortaleza, Ceará, 60451-970, Brasil
| | - David B Medeiros
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, Potsdam-Golm, 14476, Germany
- Max-Planck Partner Group at the Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, Minas Gerais, 36570-900, Brasil
| | - Letícia Dos Anjos
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, Fortaleza, Ceará, 60451-970, Brasil
| | - Takuya Yoshida
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, Potsdam-Golm, 14476, Germany
| | - Wagner L Araújo
- Max-Planck Partner Group at the Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, Minas Gerais, 36570-900, Brasil
| | - Alisdair R Fernie
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, Potsdam-Golm, 14476, Germany
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Ramesh SA, Tyerman SD, Gilliham M, Xu B. γ-Aminobutyric acid (GABA) signalling in plants. Cell Mol Life Sci 2017; 74:1577-1603. [PMID: 27838745 PMCID: PMC11107511 DOI: 10.1007/s00018-016-2415-7] [Citation(s) in RCA: 170] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 11/06/2016] [Accepted: 11/08/2016] [Indexed: 01/11/2023]
Abstract
The role of γ-aminobutyric acid (GABA) as a signal in animals has been documented for over 60 years. In contrast, evidence that GABA is a signal in plants has only emerged in the last 15 years, and it was not until last year that a mechanism by which this could occur was identified-a plant 'GABA receptor' that inhibits anion passage through the aluminium-activated malate transporter family of proteins (ALMTs). ALMTs are multigenic, expressed in different organs and present on different membranes. We propose GABA regulation of ALMT activity could function as a signal that modulates plant growth, development, and stress response. In this review, we compare and contrast the plant 'GABA receptor' with mammalian GABAA receptors in terms of their molecular identity, predicted topology, mode of action, and signalling roles. We also explore the implications of the discovery that GABA modulates anion flux in plants, its role in signal transduction for the regulation of plant physiology, and predict the possibility that there are other GABA interaction sites in the N termini of ALMT proteins through in silico evolutionary coupling analysis; we also explore the potential interactions between GABA and other signalling molecules.
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Affiliation(s)
- Sunita A Ramesh
- Plant Transport and Signalling Lab, ARC Centre of Excellence in Plant Energy Biology and School of Agriculture, Food and Wine, Waite Research Institute, University of Adelaide, Glen Osmond, SA, 5064, Australia
| | - Stephen D Tyerman
- Plant Transport and Signalling Lab, ARC Centre of Excellence in Plant Energy Biology and School of Agriculture, Food and Wine, Waite Research Institute, University of Adelaide, Glen Osmond, SA, 5064, Australia
| | - Matthew Gilliham
- Plant Transport and Signalling Lab, ARC Centre of Excellence in Plant Energy Biology and School of Agriculture, Food and Wine, Waite Research Institute, University of Adelaide, Glen Osmond, SA, 5064, Australia
| | - Bo Xu
- Plant Transport and Signalling Lab, ARC Centre of Excellence in Plant Energy Biology and School of Agriculture, Food and Wine, Waite Research Institute, University of Adelaide, Glen Osmond, SA, 5064, Australia.
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Zhang H, Zhao FG, Tang RJ, Yu Y, Song J, Wang Y, Li L, Luan S. Two tonoplast MATE proteins function as turgor-regulating chloride channels in Arabidopsis. Proc Natl Acad Sci U S A 2017; 114:E2036-E2045. [PMID: 28202726 PMCID: PMC5347570 DOI: 10.1073/pnas.1616203114] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The central vacuole in a plant cell occupies the majority of the cellular volume and plays a key role in turgor regulation. The vacuolar membrane (tonoplast) contains a large number of transporters that mediate fluxes of solutes and water, thereby adjusting cell turgor in response to developmental and environmental signals. We report that two tonoplast Detoxification efflux carrier (DTX)/Multidrug and Toxic Compound Extrusion (MATE) transporters, DTX33 and DTX35, function as chloride channels essential for turgor regulation in Arabidopsis Ectopic expression of each transporter in Nicotiana benthamiana mesophyll cells elicited a large voltage-dependent inward chloride current across the tonoplast, showing that DTX33 and DTX35 each constitute a functional channel. Both channels are highly expressed in Arabidopsis tissues, including root hairs and guard cells that experience rapid turgor changes during root-hair elongation and stomatal movements. Disruption of these two genes, either in single or double mutants, resulted in shorter root hairs and smaller stomatal aperture, with double mutants showing more severe defects, suggesting that these two channels function additively to facilitate anion influx into the vacuole during cell expansion. In addition, dtx35 single mutant showed lower fertility as a result of a defect in pollen-tube growth. Indeed, patch-clamp recording of isolated vacuoles indicated that the inward chloride channel activity across the tonoplast was impaired in the double mutant. Because MATE proteins are widely known transporters of organic compounds, finding MATE members as chloride channels expands the functional definition of this large family of transporters.
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Affiliation(s)
- Haiwen Zhang
- Institute of Plant Molecular Biology, State Key Laboratory of Pharmaceutical Technology, School of Life Sciences, Nanjing University, Nanjing 210093, China
- College of Life Sciences, Capital Normal University, Beijing 100048, China
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720
- Beijing Key Laboratory of Agricultural Genetic Resources and Biotechnology, Beijing Agro-Biotechnology Research Center, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China
| | - Fu-Geng Zhao
- Institute of Plant Molecular Biology, State Key Laboratory of Pharmaceutical Technology, School of Life Sciences, Nanjing University, Nanjing 210093, China;
| | - Ren-Jie Tang
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720
| | - Yuexuan Yu
- College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Jiali Song
- College of Life Sciences, Capital Normal University, Beijing 100048, China
| | - Yuan Wang
- Institute of Plant Molecular Biology, State Key Laboratory of Pharmaceutical Technology, School of Life Sciences, Nanjing University, Nanjing 210093, China
| | - Legong Li
- College of Life Sciences, Capital Normal University, Beijing 100048, China;
| | - Sheng Luan
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720;
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Sharma T, Dreyer I, Kochian L, Piñeros MA. The ALMT Family of Organic Acid Transporters in Plants and Their Involvement in Detoxification and Nutrient Security. FRONTIERS IN PLANT SCIENCE 2016; 7:1488. [PMID: 27757118 PMCID: PMC5047901 DOI: 10.3389/fpls.2016.01488] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2016] [Accepted: 09/20/2016] [Indexed: 05/02/2023]
Abstract
About a decade ago, members of a new protein family of anion channels were discovered on the basis of their ability to confer on plants the tolerance toward toxic aluminum ions in the soil. The efflux of Al3+-chelating malate anions through these channels is stimulated by external Al3+ ions. This feature of a few proteins determined the name of the entire protein family as Aluminum-activated Malate Transporters (ALMT). Meanwhile, after several years of research, it is known that the physiological roles of ALMTs go far beyond Al-detoxification. In this review article we summarize the current knowledge on this transporter family and assess their involvement in diverse physiological processes.
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Affiliation(s)
- Tripti Sharma
- Centro de Bioinformática y Simulación Molecular, Facultad de Ingeniería, Universidad de Talca, TalcaChile
| | - Ingo Dreyer
- Centro de Bioinformática y Simulación Molecular, Facultad de Ingeniería, Universidad de Talca, TalcaChile
| | - Leon Kochian
- Robert W. Holley Center for Agriculture and Health, United States Department of Agriculture–Agricultural Research Service, Cornell University, Ithaca, NYUSA
| | - Miguel A. Piñeros
- Robert W. Holley Center for Agriculture and Health, United States Department of Agriculture–Agricultural Research Service, Cornell University, Ithaca, NYUSA
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28
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Sasaki T, Tsuchiya Y, Ariyoshi M, Ryan PR, Yamamoto Y. A chimeric protein of aluminum-activated malate transporter generated from wheat and Arabidopsis shows enhanced response to trivalent cations. BIOCHIMICA ET BIOPHYSICA ACTA 2016; 1858:1427-35. [PMID: 27039280 DOI: 10.1016/j.bbamem.2016.03.026] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 03/16/2016] [Accepted: 03/29/2016] [Indexed: 11/19/2022]
Abstract
TaALMT1 from wheat (Triticum aestivum) and AtALMT1 from Arabidopsis thaliana encode aluminum (Al)-activated malate transporters, which confer acid-soil tolerance by releasing malate from roots. Chimeric proteins from TaALMT1 and AtALMT1 (Ta::At, At::Ta) were previously analyzed in Xenopus laevis oocytes. Those studies showed that Al could activate malate efflux from the Ta::At chimera but not from At::Ta. Here, functions of TaALMT1, AtALMT1 and the chimeric protein Ta::At were compared in cultured tobacco BY-2 cells. We focused on the sensitivity and specificity of their activation by trivalent cations. The activation of malate efflux by Al was at least two-fold greater in the chimera than the native proteins. All proteins were also activated by lanthanides (erbium, ytterbium, gadolinium, and lanthanum), but the chimera again released more malate than TaALMT1 or AtALMT1. In Xenopus oocytes, Al, ytterbium, and erbium activated inward currents from the native TaALMT1 and the chimeric protein, but gadolinium only activated currents from the chimera. Lanthanum inhibited currents from both proteins. These results demonstrated that function of the chimera protein was altered compared to the native proteins and was more responsive to a range of trivalent cations when expressed in plant cells.
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Affiliation(s)
- Takayuki Sasaki
- Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki, Okayama 710-0046, Japan.
| | - Yoshiyuki Tsuchiya
- Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki, Okayama 710-0046, Japan
| | - Michiyo Ariyoshi
- Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki, Okayama 710-0046, Japan
| | - Peter R Ryan
- CSIRO Agriculture, GPO Box 1600, Canberra, ACT, 2601, Australia
| | - Yoko Yamamoto
- Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki, Okayama 710-0046, Japan
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29
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Larisch N, Kirsch SA, Schambony A, Studtrucker T, Böckmann RA, Dietrich P. The function of the two-pore channel TPC1 depends on dimerization of its carboxy-terminal helix. Cell Mol Life Sci 2016; 73:2565-81. [PMID: 26781468 PMCID: PMC4894940 DOI: 10.1007/s00018-016-2131-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 12/07/2015] [Accepted: 01/04/2016] [Indexed: 12/12/2022]
Abstract
Two-pore channels (TPCs) constitute a family of intracellular cation channels with diverse permeation properties and functions in animals and plants. In the model plant Arabidopsis, the vacuolar cation channel TPC1 is involved in propagation of calcium waves and in cation homeostasis. Here, we discovered that the dimerization of a predicted helix within the carboxyl-terminus (CTH) is essential for the activity of TPC1. Bimolecular fluorescence complementation and co-immunoprecipitation demonstrated the interaction of the two C-termini and pointed towards the involvement of the CTH in this process. Synthetic CTH peptides dimerized with a dissociation constant of 3.9 µM. Disruption of this domain in TPC1 either by deletion or point mutations impeded the dimerization and cation transport. The homo-dimerization of the CTH was analyzed in silico using coarse-grained molecular dynamics (MD) simulations for the study of aggregation, followed by atomistic MD simulations. The simulations revealed that the helical region of the wild type, but not a mutated CTH forms a highly stable, antiparallel dimer with characteristics of a coiled-coil. We propose that the voltage- and Ca(2+)-sensitive conformation of TPC1 depends on C-terminal dimerization, adding an additional layer to the complex regulation of two-pore cation channels.
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Affiliation(s)
- Nina Larisch
- Molecular Plant Physiology, Department of Biology, University of Erlangen-Nürnberg, Staudtstrasse 5, 91058, Erlangen, Germany
| | - Sonja A Kirsch
- Computational Biology, Department of Biology, University of Erlangen-Nürnberg, Staudtstrasse 5, 91058, Erlangen, Germany
| | - Alexandra Schambony
- Developmental Biology, Department of Biology, University of Erlangen-Nürnberg, Staudtstrasse 5, 91058, Erlangen, Germany
| | - Tanja Studtrucker
- Molecular Plant Physiology, Department of Biology, University of Erlangen-Nürnberg, Staudtstrasse 5, 91058, Erlangen, Germany
| | - Rainer A Böckmann
- Computational Biology, Department of Biology, University of Erlangen-Nürnberg, Staudtstrasse 5, 91058, Erlangen, Germany
| | - Petra Dietrich
- Molecular Plant Physiology, Department of Biology, University of Erlangen-Nürnberg, Staudtstrasse 5, 91058, Erlangen, Germany.
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30
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Palmer AJ, Baker A, Muench SP. The varied functions of aluminium-activated malate transporters-much more than aluminium resistance. Biochem Soc Trans 2016; 44:856-62. [PMID: 27284052 PMCID: PMC5264499 DOI: 10.1042/bst20160027] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Indexed: 12/23/2022]
Abstract
The ALMT (aluminium-activated malate transporter) family comprises a functionally diverse but structurally similar group of ion channels. They are found ubiquitously in plant species, expressed throughout different tissues, and located in either the plasma membrane or tonoplast. The first family member identified was TaALMT1, discovered in wheat root tips, which was found to be involved in aluminium resistance by means of malate exudation into the soil. However, since this discovery other family members have been shown to have many other functions such as roles in stomatal opening, general anionic homoeostasis, and in economically valuable traits such as fruit flavour. Recent evidence has also shown that ALMT proteins can act as key molecular actors in GABA (γ-aminobutyric acid) signalling, the first evidence that GABA can act as a signal transducer in plants.
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Affiliation(s)
- Antony J Palmer
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K. Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, U.K. Centre for Plant Science, University of Leeds, Leeds LS2 9JT, U.K
| | - Alison Baker
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, U.K. Centre for Plant Science, University of Leeds, Leeds LS2 9JT, U.K. School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K
| | - Stephen P Muench
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K. Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, U.K. )
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Jaborsky M, Maierhofer T, Olbrich A, Escalante-Pérez M, Müller HM, Simon J, Krol E, Cuin TA, Fromm J, Ache P, Geiger D, Hedrich R. SLAH3-type anion channel expressed in poplar secretory epithelia operates in calcium kinase CPK-autonomous manner. THE NEW PHYTOLOGIST 2016; 210:922-33. [PMID: 26831448 DOI: 10.1111/nph.13841] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 12/03/2015] [Indexed: 05/14/2023]
Abstract
Extrafloral nectaries secrete a sweet sugar cocktail that lures predator insects for protection from foraging herbivores. Apart from sugars and amino acids, the nectar contains the anions chloride and nitrate. Recent studies with Populus have identified a type of nectary covered by apical bipolar epidermal cells, reminiscent of the secretory brush border epithelium in animals. Border epithelia operate transepithelial anion transport, which is required for membrane potential and/or osmotic adjustment of the secretory cells. In search of anion transporters expressed in extrafloral nectaries, we identified PttSLAH3 (Populus tremula × Populus tremuloides SLAC1 Homologue3), an anion channel of the SLAC/SLAH family. When expressed in Xenopus oocytes, PttSLAH3 displayed the features of a voltage-dependent anion channel, permeable to both nitrate and chloride. In contrast to the Arabidopsis SLAC/SLAH family members, the poplar isoform PttSLAH3 is independent of phosphorylation activation by protein kinases. To understand the basis for the autonomous activity of the poplar SLAH3, we generated and expressed chimera between kinase-independent PttSLAH3 and kinase-dependent Arabidopsis AtSLAH3. We identified the N-terminal tail and, to a lesser extent, the C-terminal tail as responsible for PttSLAH3 kinase-(in)dependent action. This feature of PttSLAH3 may provide the secretory cell with a channel probably controlling long-term nectar secretion.
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Affiliation(s)
- Mario Jaborsky
- University Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Julius-von-Sachs-Platz 2, Würzburg, D-97082, Germany
| | - Tobias Maierhofer
- University Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Julius-von-Sachs-Platz 2, Würzburg, D-97082, Germany
| | - Andrea Olbrich
- Thünen Institute of Wood Research, Leuschnerstr. 91d, Hamburg, 21031, Germany
| | - María Escalante-Pérez
- University Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Julius-von-Sachs-Platz 2, Würzburg, D-97082, Germany
| | - Heike M Müller
- University Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Julius-von-Sachs-Platz 2, Würzburg, D-97082, Germany
| | - Judy Simon
- Chair of Tree Physiology, University of Freiburg, Freiburg, 79110, Germany
| | - Elzbieta Krol
- University Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Julius-von-Sachs-Platz 2, Würzburg, D-97082, Germany
| | - Tracey Ann Cuin
- University Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Julius-von-Sachs-Platz 2, Würzburg, D-97082, Germany
| | - Jörg Fromm
- Center for Wood Sciences, University of Hamburg, Leuschnerstr. 91, Hamburg, 21031, Germany
| | - Peter Ache
- University Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Julius-von-Sachs-Platz 2, Würzburg, D-97082, Germany
| | - Dietmar Geiger
- University Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Julius-von-Sachs-Platz 2, Würzburg, D-97082, Germany
| | - Rainer Hedrich
- University Würzburg, Biozentrum, Julius-von-Sachs-Institut für Biowissenschaften, Julius-von-Sachs-Platz 2, Würzburg, D-97082, Germany
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Hedrich R, Salvador-Recatalà V, Dreyer I. Electrical Wiring and Long-Distance Plant Communication. TRENDS IN PLANT SCIENCE 2016; 21:376-387. [PMID: 26880317 DOI: 10.1016/j.tplants.2016.01.016] [Citation(s) in RCA: 135] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Revised: 01/06/2016] [Accepted: 01/18/2016] [Indexed: 05/18/2023]
Abstract
Electrical signalling over long distances is an efficient way of achieving cell-to-cell communication in living organisms. In plants, the phloem can be considered as a 'green cable' that allows the transmission of action potentials (APs) induced by stimuli such as wounding and cold. Measuring phloem potential changes and separating them from secondary responses of surrounding tissues can be achieved using living aphids as bioelectrodes. Two glutamate receptor-like genes (GLR3.3 and 3.6) were identified as being involved in the propagation of electrical activity from the damaged to undamaged leaves. However, phloem APs are initiated and propagated independently of these glutamate receptors. Here, we propose new screening approaches to obtain further information on the components required for electrical signalling in phloem cables.
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Affiliation(s)
- Rainer Hedrich
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs-Platz 2, 97082 Würzburg, Germany.
| | - Vicenta Salvador-Recatalà
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs-Platz 2, 97082 Würzburg, Germany
| | - Ingo Dreyer
- Centro de Bioinformática y Simulación Molecular (CBSM), Universidad de Talca, 2 Norte 685, Talca, Chile.
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Kochian LV, Piñeros MA, Liu J, Magalhaes JV. Plant Adaptation to Acid Soils: The Molecular Basis for Crop Aluminum Resistance. ANNUAL REVIEW OF PLANT BIOLOGY 2015; 66:571-98. [PMID: 25621514 DOI: 10.1146/annurev-arplant-043014-114822] [Citation(s) in RCA: 502] [Impact Index Per Article: 50.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Aluminum (Al) toxicity in acid soils is a significant limitation to crop production worldwide, as approximately 50% of the world's potentially arable soil is acidic. Because acid soils are such an important constraint to agriculture, understanding the mechanisms and genes conferring resistance to Al toxicity has been a focus of intense research interest in the decade since the last article on crop acid soil tolerance was published in this journal. An impressive amount of progress has been made during that time that has greatly increased our understanding of the diversity of Al resistance genes and mechanisms, how resistance gene expression is regulated and triggered by Al and Al-induced signals, and how the proteins encoded by these genes function and are regulated. This review examines the state of our understanding of the physiological, genetic, and molecular bases for crop Al tolerance, looking at the novel Al resistance genes and mechanisms that have been identified over the past ten years. Additionally, it examines how the integration of molecular and genetic analyses of crop Al resistance is starting to be exploited for the improvement of crop plants grown on acid soils via both molecular-assisted breeding and biotechnology approaches.
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Affiliation(s)
- Leon V Kochian
- Robert W. Holley Center for Agriculture and Health, USDA-ARS, Cornell University, Ithaca, New York 14853; , ,
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Sasaki T, Tsuchiya Y, Ariyoshi M, Ryan PR, Furuichi T, Yamamoto Y. A domain-based approach for analyzing the function of aluminum-activated malate transporters from wheat (Triticum aestivum) and Arabidopsis thaliana in Xenopus oocytes. PLANT & CELL PHYSIOLOGY 2014; 55:2126-38. [PMID: 25311199 DOI: 10.1093/pcp/pcu143] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Wheat and Arabidopsis plants respond to aluminum (Al) ions by releasing malate from their root apices via Al-activated malate transporter. Malate anions bind with the toxic Al ions and contribute to the Al tolerance of these species. The genes encoding the transporters in wheat and Arabidopsis, TaALMT1 and AtALMT1, respectively, were expressed in Xenopus laevis oocytes and characterized electrophysiologically using the two-electrode voltage clamp system. The Al-activated currents generated by malate efflux were detected for TaALMT1 but not for AtALMT1. Chimeric proteins were generated by swapping the N- and C-terminal halves of TaALMT1 and AtALMT1 (Ta::At and At::Ta). When these chimeras were characterized in oocytes, Al-activated malate efflux was detected for the Ta::At chimera but not for At::Ta, suggesting that the N-terminal half of TaALMT1 is necessary for function in oocytes. An additional chimera, Ta(48)::At, generated by swapping 17 residues from the N-terminus of AtALMT1 with the equivalent 48 residues from TaALMT1, was sufficient to support transport activity. This 48 residue region includes a helical region with a putative transmembrane domain which is absent in AtALMT1. The deletion of this domain from Ta(48)::At led to the complete loss of transport activity. Furthermore, truncations and a deletion at the C-terminal end of TaALMT1 indicated that a putative helical structure in this region was also required for transport function. This study provides insights into the structure-function relationships of Al-activated ALMT proteins by identifying specific domains on the N- and C-termini of TaALMT1 that are critical for basal transport function and Al responsiveness in oocytes.
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Affiliation(s)
- Takayuki Sasaki
- Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki, Okayama, 710-0046 Japan
| | - Yoshiyuki Tsuchiya
- Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki, Okayama, 710-0046 Japan
| | - Michiyo Ariyoshi
- Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki, Okayama, 710-0046 Japan
| | - Peter R Ryan
- CSIRO Agriculture, GPO Box 1600, Canberra, ACT 2601, Australia
| | - Takuya Furuichi
- Department of Health and Nutrition, Faculty of Home Economics, Gifu Women's University, Taromaru 80, Gifu, 501-2592 Japan
| | - Yoko Yamamoto
- Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki, Okayama, 710-0046 Japan
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Häusler RE, Ludewig F, Krueger S. Amino acids--a life between metabolism and signaling. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2014; 229:225-237. [PMID: 25443849 DOI: 10.1016/j.plantsci.2014.09.011] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 09/18/2014] [Accepted: 09/19/2014] [Indexed: 05/09/2023]
Abstract
Amino acids serve as constituents of proteins, precursors for anabolism, and, in some cases, as signaling molecules in mammalians and plants. This review is focused on new insights, or speculations, on signaling functions of serine, γ-aminobutyric acid (GABA) and phenylalanine-derived phenylpropanoids. Serine acts as signal in brain tissue and mammalian cancer cells. In plants, de novo serine biosynthesis is also highly active in fast growing tissues such as meristems, suggesting a similar role of serine as in mammalians. GABA functions as inhibitory neurotransmitter in the brain. In plants, GABA is also abundant and seems to be involved in sexual reproduction, cell elongation, patterning and cell identity. The aromatic amino acids phenylalanine, tyrosine, and tryptophan are precursors for the production of secondary plant products. Besides their pharmaceutical value, lignans, neolignans and hydroxycinnamic acid amides (HCAA) deriving from phenylpropanoid metabolism and, in the case of HCAA, also from arginine have been shown to fulfill signaling functions or are involved in the response to biotic and abiotic stress. Although some basics on phenylpropanoid-derived signaling have been described, little is known on recognition- or signal transduction mechanisms. In general, mutant- and transgenic approaches will be helpful to elucidate the mechanistic basis of metabolite signaling.
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Affiliation(s)
- Rainer E Häusler
- Department of Botany II, University of Cologne, Cologne Biocenter, Zülpicherstr. 47B, 50674 Cologne, Germany.
| | - Frank Ludewig
- Department of Botany II, University of Cologne, Cologne Biocenter, Zülpicherstr. 47B, 50674 Cologne, Germany
| | - Stephan Krueger
- Department of Botany II, University of Cologne, Cologne Biocenter, Zülpicherstr. 47B, 50674 Cologne, Germany
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Lawson T, Simkin AJ, Kelly G, Granot D. Mesophyll photosynthesis and guard cell metabolism impacts on stomatal behaviour. THE NEW PHYTOLOGIST 2014; 203:1064-1081. [PMID: 25077787 DOI: 10.1111/nph.12945] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Accepted: 06/02/2014] [Indexed: 05/19/2023]
Abstract
Stomata control gaseous fluxes between the internal leaf air spaces and the external atmosphere. Guard cells determine stomatal aperture and must operate to ensure an appropriate balance between CO2 uptake for photosynthesis (A) and water loss, and ultimately plant water use efficiency (WUE). A strong correlation between A and stomatal conductance (gs ) is well documented and often observed, but the underlying mechanisms, possible signals and metabolites that promote this relationship are currently unknown. In this review we evaluate the current literature on mesophyll-driven signals that may coordinate stomatal behaviour with mesophyll carbon assimilation. We explore a possible role of various metabolites including sucrose and malate (from several potential sources; including guard cell photosynthesis) and new evidence that improvements in WUE have been made by manipulating sucrose metabolism within the guard cells. Finally we discuss the new tools and techniques available for potentially manipulating cell-specific metabolism, including guard and mesophyll cells, in order to elucidate mesophyll-derived signals that coordinate mesophyll CO2 demands with stomatal behaviour, in order to provide a mechanistic understanding of these processes as this may identify potential targets for manipulations in order to improve plant WUE and crop yield.
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Affiliation(s)
- Tracy Lawson
- School of Biological Sciences, University of Essex, Colchester, CO4 3SQ, UK
| | - Andrew J Simkin
- School of Biological Sciences, University of Essex, Colchester, CO4 3SQ, UK
| | - Gilor Kelly
- Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Bet-Dagan, 50250, Israel
| | - David Granot
- Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Bet-Dagan, 50250, Israel
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Zhang J, Martinoia E, De Angeli A. Cytosolic nucleotides block and regulate the Arabidopsis vacuolar anion channel AtALMT9. J Biol Chem 2014; 289:25581-9. [PMID: 25028514 DOI: 10.1074/jbc.m114.576108] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The aluminum-activated malate transporters (ALMTs) form a membrane protein family exhibiting different physiological roles in plants, varying from conferring tolerance to environmental Al(3+) to the regulation of stomatal movement. The regulation of the anion channels of the ALMT family is largely unknown. Identifying intracellular modulators of the activity of anion channels is fundamental to understanding their physiological functions. In this study we investigated the role of cytosolic nucleotides in regulating the activity of the vacuolar anion channel AtALMT9. We found that cytosolic nucleotides modulate the transport activity of AtALMT9. This modulation was based on a direct block of the pore of the channel at negative membrane potentials (open channel block) by the nucleotide and not by a phosphorylation mechanism. The block by nucleotides of AtALMT9-mediated currents was voltage dependent. The blocking efficiency of intracellular nucleotides increased with the number of phosphate groups and ATP was the most effective cellular blocker. Interestingly, the ATP block induced a marked modification of the current-voltage characteristic of AtALMT9. In addition, increased concentrations of vacuolar anions were able to shift the ATP block threshold to a more negative membrane potential. The block of AtALMT9-mediated anion currents by ATP at negative membrane potentials acts as a gate of the channel and vacuolar anion tune this gating mechanism. Our results suggest that anion transport across the vacuolar membrane in plant cells is controlled by cytosolic nucleotides and the energetic status of the cell.
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Affiliation(s)
- Jingbo Zhang
- From the Institute of Plant Biology, University of Zurich, CH-8008 Zurich, Switzerland and
| | - Enrico Martinoia
- From the Institute of Plant Biology, University of Zurich, CH-8008 Zurich, Switzerland and
| | - Alexis De Angeli
- From the Institute of Plant Biology, University of Zurich, CH-8008 Zurich, Switzerland and the Institut des Sciences du Végétal, CNRS, 91198 Gif-sur-Yvette, France
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Anschütz U, Becker D, Shabala S. Going beyond nutrition: regulation of potassium homoeostasis as a common denominator of plant adaptive responses to environment. JOURNAL OF PLANT PHYSIOLOGY 2014; 171:670-87. [PMID: 24635902 DOI: 10.1016/j.jplph.2014.01.009] [Citation(s) in RCA: 244] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 01/14/2014] [Accepted: 01/17/2014] [Indexed: 05/18/2023]
Abstract
Partially and fully completed plant genome sequencing projects in both lower and higher plants allow drawing a comprehensive picture of the molecular and structural diversities of plant potassium transporter genes and their encoded proteins. While the early focus of the research in this field was aimed on the structure-function studies and understanding of the molecular mechanisms underlying K(+) transport, availability of Arabidopsis thaliana mutant collections in combination with micro-array techniques have significantly advanced our understanding of K(+) channel physiology, providing novel insights into the transcriptional regulation of potassium homeostasis in plants. More recently, posttranslational regulation of potassium transport systems has moved into the center stage of potassium transport research. The current review is focused on the most exciting developments in this field. By summarizing recent work on potassium transporter regulation we show that potassium transport in general, and potassium channels in particular, represent important targets and are mediators of the cellular responses during different developmental stages in a plant's life cycle. We show that regulation of intracellular K(+) homeostasis is essential to mediate plant adaptive responses to a broad range of abiotic and biotic stresses including drought, salinity, and oxidative stress. We further link post-translational regulation of K(+) channels with programmed cell death and show that K(+) plays a critical role in controlling the latter process. Thus, is appears that K(+) is not just the essential nutrient required to support optimal plant growth and yield but is also an important signaling agent mediating a wide range of plant adaptive responses to environment.
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Affiliation(s)
- Uta Anschütz
- University of Wuerzburg, Plant Molecular Biology & Biophysics, Wuerzburg, Germany
| | - Dirk Becker
- University of Wuerzburg, Plant Molecular Biology & Biophysics, Wuerzburg, Germany.
| | - Sergey Shabala
- School of Agricultural Science, University of Tasmania, Hobart, Australia
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Ligaba A, Dreyer I, Margaryan A, Schneider DJ, Kochian L, Piñeros M. Functional, structural and phylogenetic analysis of domains underlying the Al sensitivity of the aluminum-activated malate/anion transporter, TaALMT1. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 76:766-80. [PMID: 24188189 DOI: 10.1111/tpj.12332] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 09/05/2013] [Accepted: 09/09/2013] [Indexed: 05/08/2023]
Abstract
Triticum aestivum aluminum-activated malate transporter (TaALMT1) is the founding member of a unique gene family of anion transporters (ALMTs) that mediate the efflux of organic acids. A small sub-group of root-localized ALMTs, including TaALMT1, is physiologically associated with in planta aluminum (Al) resistance. TaALMT1 exhibits significant enhancement of transport activity in response to extracellular Al. In this study, we integrated structure-function analyses of structurally altered TaALMT1 proteins expressed in Xenopus oocytes with phylogenic analyses of the ALMT family. Our aim is to re-examine the role of protein domains in terms of their potential involvement in the Al-dependent enhancement (i.e. Al-responsiveness) of TaALMT1 transport activity, as well as the roles of all its 43 negatively charged amino acid residues. Our results indicate that the N-domain, which is predicted to form the conductive pathway, mediates ion transport even in the absence of the C-domain. However, segments in both domains are involved in Al(3+) sensing. We identified two regions, one at the N-terminus and a hydrophobic region at the C-terminus, that jointly contribute to the Al-response phenotype. Interestingly, the characteristic motif at the N-terminus appears to be specific for Al-responsive ALMTs. Our study highlights the need to include a comprehensive phylogenetic analysis when drawing inferences from structure-function analyses, as a significant proportion of the functional changes observed for TaALMT1 are most likely the result of alterations in the overall structural integrity of ALMT family proteins rather than modifications of specific sites involved in Al(3+) sensing.
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Affiliation(s)
- Ayalew Ligaba
- Robert W. Holley Center for Agriculture and Health, Agricultural Research Service, US Department of Agriculture, Cornell University, Tower Road, Ithaca, NY, 14853, USA
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Zhang J, Baetz U, Krügel U, Martinoia E, De Angeli A. Identification of a probable pore-forming domain in the multimeric vacuolar anion channel AtALMT9. PLANT PHYSIOLOGY 2013; 163:830-43. [PMID: 23918900 PMCID: PMC3793061 DOI: 10.1104/pp.113.219832] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Accepted: 08/05/2013] [Indexed: 05/18/2023]
Abstract
Aluminum-activated malate transporters (ALMTs) form an important family of anion channels involved in fundamental physiological processes in plants. Because of their importance, the role of ALMTs in plant physiology is studied extensively. In contrast, the structural basis of their functional properties is largely unknown. This lack of information limits the understanding of the functional and physiological differences between ALMTs and their impact on anion transport in plants. This study aimed at investigating the structural organization of the transmembrane domain of the Arabidopsis (Arabidopsis thaliana) vacuolar channel AtALMT9. For that purpose, we performed a large-scale mutagenesis analysis and found two residues that form a salt bridge between the first and second putative transmembrane α-helices (TMα1 and TMα2). Furthermore, using a combination of pharmacological and mutagenesis approaches, we identified citrate as an "open channel blocker" of AtALMT9 and used this tool to examine the inhibition sensitivity of different point mutants of highly conserved amino acid residues. By this means, we found a stretch within the cytosolic moiety of the TMα5 that is a probable pore-forming domain. Moreover, using a citrate-insensitive AtALMT9 mutant and biochemical approaches, we could demonstrate that AtALMT9 forms a multimeric complex that is supposedly composed of four subunits. In summary, our data provide, to our knowledge, the first evidence about the structural organization of an ion channel of the ALMT family. We suggest that AtALMT9 is a tetramer and that the TMα5 domains of the subunits contribute to form the pore of this anion channel.
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Affiliation(s)
| | | | - Undine Krügel
- Institute of Plant Biology, University of Zürich, CH–8008 Zurich, Switzerland
| | - Enrico Martinoia
- Institute of Plant Biology, University of Zürich, CH–8008 Zurich, Switzerland
| | - Alexis De Angeli
- Institute of Plant Biology, University of Zürich, CH–8008 Zurich, Switzerland
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Imes D, Mumm P, Böhm J, Al-Rasheid KAS, Marten I, Geiger D, Hedrich R. Open stomata 1 (OST1) kinase controls R-type anion channel QUAC1 in Arabidopsis guard cells. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 74:372-82. [PMID: 23452338 DOI: 10.1111/tpj.12133] [Citation(s) in RCA: 129] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Revised: 01/21/2013] [Accepted: 01/23/2013] [Indexed: 05/08/2023]
Abstract
Under drought stress, the stress hormone ABA addresses the SnR kinase OST1 via its cytosolic receptor and the protein phosphatase ABI1. Upon activation, OST1 phosphorylates the guard cell S-type anion channel SLAC1. Arabidopsis ABI1 and OST1 loss-of-function mutants are characterized by an extreme wilting 'open stomata' phenotype. Given the fact that guard cells express both SLAC- and R-/QUAC-type anion channels, we questioned whether OST1, besides SLAC1, also controls the QUAC1 channel. In other words, are ABI1/OST1 defects preventing both of the guard cell anion channel types from operating properly in terms of stomatal closure? The activation of the R-/QUAC-type anion channel by ABA signaling kinase OST1 and phosphatase ABI1 was analyzed in two experimental systems: Arabidopsis guard cells and the plant cell-free background of Xenopus oocytes. Patch-clamp studies on guard cells show that ABA activates R-/QUAC-type currents of wild-type plants, but to a much lesser extent in those of abi1-1 and ost1-2 mutants. In the oocyte system the co-expression of QUAC1 and OST1 resulted in a pronounced activation of the R-type anion channel. These studies indicate that OST1 is addressing both S-/SLAC- and R-/QUAC-type guard cell anion channels, and explain why the ost1-2 mutant is much more sensitive to drought than single slac1 or quac1 mutants.
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Affiliation(s)
- Dennis Imes
- Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute, University of Würzburg, Julius-von-Sachs Platz 2, D-97082, Würzburg, Germany
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