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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: 1.5] [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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Jezek M, Blatt MR. The Membrane Transport System of the Guard Cell and Its Integration for Stomatal Dynamics. PLANT PHYSIOLOGY 2017; 174:487-519. [PMID: 28408539 PMCID: PMC5462021 DOI: 10.1104/pp.16.01949] [Citation(s) in RCA: 180] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 04/11/2017] [Indexed: 05/17/2023]
Abstract
Stomatal guard cells are widely recognized as the premier plant cell model for membrane transport, signaling, and homeostasis. This recognition is rooted in half a century of research into ion transport across the plasma and vacuolar membranes of guard cells that drive stomatal movements and the signaling mechanisms that regulate them. Stomatal guard cells surround pores in the epidermis of plant leaves, controlling the aperture of the pore to balance CO2 entry into the leaf for photosynthesis with water loss via transpiration. The position of guard cells in the epidermis is ideally suited for cellular and subcellular research, and their sensitivity to endogenous signals and environmental stimuli makes them a primary target for physiological studies. Stomata underpin the challenges of water availability and crop production that are expected to unfold over the next 20 to 30 years. A quantitative understanding of how ion transport is integrated and controlled is key to meeting these challenges and to engineering guard cells for improved water use efficiency and agricultural yields.
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Affiliation(s)
- Mareike Jezek
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Michael R Blatt
- Laboratory of Plant Physiology and Biophysics, University of Glasgow, Glasgow G12 8QQ, United Kingdom
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Gan X, Albert R. Analysis of a dynamic model of guard cell signaling reveals the stability of signal propagation. BMC SYSTEMS BIOLOGY 2016; 10:78. [PMID: 27542373 PMCID: PMC4992220 DOI: 10.1186/s12918-016-0327-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Accepted: 08/11/2016] [Indexed: 11/10/2022]
Abstract
BACKGROUND Analyzing the long-term behaviors (attractors) of dynamic models of biological systems can provide valuable insight into biological phenotypes and their stability. In this paper we identify the allowed long-term behaviors of a multi-level, 70-node dynamic model of the stomatal opening process in plants. RESULTS We start by reducing the model's huge state space. We first reduce unregulated nodes and simple mediator nodes, then simplify the regulatory functions of selected nodes while keeping the model consistent with experimental observations. We perform attractor analysis on the resulting 32-node reduced model by two methods: 1. converting it into a Boolean model, then applying two attractor-finding algorithms; 2. theoretical analysis of the regulatory functions. We further demonstrate the robustness of signal propagation by showing that a large percentage of single-node knockouts does not affect the stomatal opening level. CONCLUSIONS Combining both methods with analysis of perturbation scenarios, we conclude that all nodes except two in the reduced model have a single attractor; and only two nodes can admit oscillations. The multistability or oscillations of these four nodes do not affect the stomatal opening level in any situation. This conclusion applies to the original model as well in all the biologically meaningful cases. In addition, the stomatal opening level is resilient against single-node knockouts. Thus, we conclude that the complex structure of this signal transduction network provides multiple information propagation pathways while not allowing extensive multistability or oscillations, resulting in robust signal propagation. Our innovative combination of methods offers a promising way to analyze multi-level models.
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Affiliation(s)
- Xiao Gan
- Department of Physics, The Pennsylvania State University, University Park, PA USA
| | - Réka Albert
- Department of Physics, The Pennsylvania State University, University Park, PA USA
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Yang R, Hui Q, Gu Z. Effects of ABA and CaCl2 on GABA accumulation in fava bean germinating under hypoxia-NaCl stress. Biosci Biotechnol Biochem 2016; 80:540-6. [DOI: 10.1080/09168451.2015.1116923] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Abstract
Effects of exogenous abscisic acid (ABA) and CaCl2 on γ-aminobutyric acid (GABA) accumulation of germinated fava bean under hypoxia-NaCl stress were investigated. Exogenous ABA resulted in the enhancement of glutamate decarboxylase (GAD) and diamine oxidase (DAO) activity as well as GABA content in cotyledon and shoot. CaCl2 increased both enzyme activities in shoot and GABA content in cotyledon and shoot. ABA downregulated GAD expression in cotyledon and radicle, while upregulated that in shoot; it also upregulated DAO expression in each organ. CaCl2 upregulated GAD expression in cotyledon, while downregulated that in radicle. However, it upregulated DAO expression in shoot, downregulated that in radicle. ABA inhibitor fluridon and ethylenediaminetetraacetic acid inhibited GAD and DAO activities significantly so that inhibited GABA accumulation through reducing ABA biosynthesis and chelating Ca2+, respectively. However, they upregulated GAD and DAO expression in varying degrees. These results indicate that ABA and Ca2+ participate in GABA biosynthesis in fava bean during germination under hypoxia-NaCl stress.
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Affiliation(s)
- Runqiang Yang
- College of Food Science and Technology, Nanjing Agricultural University, Nanjing, People’s Republic of China
| | - Qianru Hui
- College of Food Science and Technology, Nanjing Agricultural University, Nanjing, People’s Republic of China
| | - Zhenxin Gu
- College of Food Science and Technology, Nanjing Agricultural University, Nanjing, People’s Republic of China
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Komatsu S, Kamal AHM, Hossain Z. Wheat proteomics: proteome modulation and abiotic stress acclimation. FRONTIERS IN PLANT SCIENCE 2014; 5:684. [PMID: 25538718 PMCID: PMC4259124 DOI: 10.3389/fpls.2014.00684] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2014] [Accepted: 11/18/2014] [Indexed: 05/21/2023]
Abstract
Cellular mechanisms of stress sensing and signaling represent the initial plant responses to adverse conditions. The development of high-throughput "Omics" techniques has initiated a new era of the study of plant molecular strategies for adapting to environmental changes. However, the elucidation of stress adaptation mechanisms in plants requires the accurate isolation and characterization of stress-responsive proteins. Because the functional part of the genome, namely the proteins and their post-translational modifications, are critical for plant stress responses, proteomic studies provide comprehensive information about the fine-tuning of cellular pathways that primarily involved in stress mitigation. This review summarizes the major proteomic findings related to alterations in the wheat proteomic profile in response to abiotic stresses. Moreover, the strengths and weaknesses of different sample preparation techniques, including subcellular protein extraction protocols, are discussed in detail. The continued development of proteomic approaches in combination with rapidly evolving bioinformatics tools and interactive databases will facilitate understanding of the plant mechanisms underlying stress tolerance.
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Affiliation(s)
- Setsuko Komatsu
- National Institute of Crop Science, National Agriculture and Food Research OrganizationTsukuba, Japan
| | - Abu H. M. Kamal
- National Institute of Crop Science, National Agriculture and Food Research OrganizationTsukuba, Japan
| | - Zahed Hossain
- Plant Stress Biology Lab, Department of Botany, West Bengal State UniversityKolkata, India
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Sun Z, Jin X, Albert R, Assmann SM. Multi-level modeling of light-induced stomatal opening offers new insights into its regulation by drought. PLoS Comput Biol 2014; 10:e1003930. [PMID: 25393147 PMCID: PMC4230748 DOI: 10.1371/journal.pcbi.1003930] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Accepted: 09/19/2014] [Indexed: 12/17/2022] Open
Abstract
Plant guard cells gate CO2 uptake and transpirational water loss through stomatal pores. As a result of decades of experimental investigation, there is an abundance of information on the involvement of specific proteins and secondary messengers in the regulation of stomatal movements and on the pairwise relationships between guard cell components. We constructed a multi-level dynamic model of guard cell signal transduction during light-induced stomatal opening and of the effect of the plant hormone abscisic acid (ABA) on this process. The model integrates into a coherent network the direct and indirect biological evidence regarding the regulation of seventy components implicated in stomatal opening. Analysis of this signal transduction network identified robust cross-talk between blue light and ABA, in which [Ca2+]c plays a key role, and indicated an absence of cross-talk between red light and ABA. The dynamic model captured more than 10(31) distinct states for the system and yielded outcomes that were in qualitative agreement with a wide variety of previous experimental results. We obtained novel model predictions by simulating single component knockout phenotypes. We found that under white light or blue light, over 60%, and under red light, over 90% of all simulated knockouts had similar opening responses as wild type, showing that the system is robust against single node loss. The model revealed an open question concerning the effect of ABA on red light-induced stomatal opening. We experimentally showed that ABA is able to inhibit red light-induced stomatal opening, and our model offers possible hypotheses for the underlying mechanism, which point to potential future experiments. Our modelling methodology combines simplicity and flexibility with dynamic richness, making it well suited for a wide class of biological regulatory systems.
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Affiliation(s)
- Zhongyao Sun
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Xiaofen Jin
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Réka Albert
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania, United States of America
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Sarah M. Assmann
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
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Burdach Z, Kurtyka R, Siemieniuk A, Karcz W. Role of chloride ions in the promotion of auxin-induced growth of maize coleoptile segments. ANNALS OF BOTANY 2014; 114:1023-34. [PMID: 25129632 PMCID: PMC4171079 DOI: 10.1093/aob/mcu170] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 07/01/2014] [Indexed: 05/23/2023]
Abstract
BACKGROUND AND AIMS The mechanism of auxin action on ion transport in growing cells has not been determined in detail. In particular, little is known about the role of chloride in the auxin-induced growth of coleoptile cells. Moreover, the data that do exist in the literature are controversial. This study describes experiments that were carried out with maize (Zea mays) coleoptile segments, this being a classical model system for studies of plant cell elongation growth. METHODS Growth kinetics or growth and pH changes were recorded in maize coleoptiles using two independent measuring systems. The growth rate of the segments was measured simultaneously with medium pH changes. Membrane potential changes in parenchymal cells of the segments were also determined for chosen variants. The question of whether anion transport is involved in auxin-induced growth of maize coleoptile segments was primarily studied using anion channel blockers [anthracene-9-carboxylic acid (A-9-C) and 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS)]. In addition, experiments in which KCl was replaced by KNO3 were also performed. KEY RESULTS Both anion channel blockers, added at 0·1 mm, diminished indole-3-acetic acid (IAA)-induced elongation growth by ~30 %. Medium pH changes measured simultaneously with growth indicated that while DIDS stopped IAA-induced proton extrusion, A-9-C diminished it by only 50 %. Addition of A-9-C to medium containing 1 mm KCl did not affect the characteristic kinetics of IAA-induced membrane potential changes, while in the presence of 10 mm KCl the channel blocker stopped IAA-induced membrane hyperpolarization. Replacement of KCl with KNO3 significantly decreased IAA-induced growth and inhibited proton extrusion. In contrast to the KCl concentration, the concentration of KNO3 did not affect the growth-stimulatory effect of IAA. For comparison, the effects of the cation channel blocker tetraethylammonium chloride (TEA-Cl) on IAA-induced growth and proton extrusion were also determined. TEA-Cl, added 1 h before IAA, caused reduction of growth by 49·9 % and inhibition of proton extrusion. CONCLUSIONS These results suggest that Cl(-) plays a role in the IAA-induced growth of maize coleoptile segments. A possible mechanism for Cl(-) uptake during IAA-induced growth is proposed in which uptake of K(+) and Cl(-) ions in concert with IAA-induced plasma membrane H(+)-ATPase activity changes the membrane potential to a value needed for turgor adjustment during the growth of maize coleoptile cells.
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Affiliation(s)
- Zbigniew Burdach
- Department of Plant Physiology, Faculty of Biology and Environmental Protection, University of Silesia, Jagiellońska 28, PL-40-032 Katowice, Poland
| | - Renata Kurtyka
- Department of Plant Physiology, Faculty of Biology and Environmental Protection, University of Silesia, Jagiellońska 28, PL-40-032 Katowice, Poland
| | - Agnieszka Siemieniuk
- Department of Plant Physiology, Faculty of Biology and Environmental Protection, University of Silesia, Jagiellońska 28, PL-40-032 Katowice, Poland
| | - Waldemar Karcz
- Department of Plant Physiology, Faculty of Biology and Environmental Protection, University of Silesia, Jagiellońska 28, PL-40-032 Katowice, Poland
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Miura K, Tada Y. Regulation of water, salinity, and cold stress responses by salicylic acid. FRONTIERS IN PLANT SCIENCE 2014; 5:4. [PMID: 24478784 PMCID: PMC3899523 DOI: 10.3389/fpls.2014.00004] [Citation(s) in RCA: 281] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Accepted: 01/04/2014] [Indexed: 05/18/2023]
Abstract
Salicylic acid (SA) is a naturally occurring phenolic compound. SA plays an important role in the regulation of plant growth, development, ripening, and defense responses. The role of SA in the plant-pathogen relationship has been extensively investigated. In addition to defense responses, SA plays an important role in the response to abiotic stresses, including drought, low temperature, and salinity stresses. It has been suggested that SA has great agronomic potential to improve the stress tolerance of agriculturally important crops. However, the utility of SA is dependent on the concentration of the applied SA, the mode of application, and the state of the plants (e.g., developmental stage and acclimation). Generally, low concentrations of applied SA alleviate the sensitivity to abiotic stresses, and high concentrations of applied induce high levels of oxidative stress, leading to a decreased tolerance to abiotic stresses. In this article, the effects of SA on the water stress responses and regulation of stomatal closure are reviewed.
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Affiliation(s)
- Kenji Miura
- Faculty of Life and Environmental Sciences, University of TsukubaTsukuba, Japan
- *Correspondence: Kenji* Miura, Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8572, Japan e-mail:
| | - Yasuomi Tada
- Faculty of Agriculture, Kagawa UniversityKagawa, Japan
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Mumm P, Imes D, Martinoia E, Al-Rasheid KAS, Geiger D, Marten I, Hedrich R. C-terminus-mediated voltage gating of Arabidopsis guard cell anion channel QUAC1. MOLECULAR PLANT 2013; 6:1550-63. [PMID: 23314055 DOI: 10.1093/mp/sst008] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Anion transporters in plants play a fundamental role in volume regulation and signaling. Currently, two plasma membrane-located anion channel families—SLAC/SLAH and ALMT—are known. Among the ALMT family, the root-expressed ALuminium-activated Malate Transporter 1 was identified by comparison of aluminum-tolerant and Al(3+)-sensitive wheat cultivars and was subsequently shown to mediate voltage-independent malate currents. In contrast, ALMT12/QUAC1 (QUickly activating Anion Channel1) is expressed in guard cells transporting malate in an Al(3+)-insensitive and highly voltage-dependent manner. So far, no information is available about the structure and mechanism of voltage-dependent gating with the QUAC1 channel protein. Here, we analyzed gating of QUAC1-type currents in the plasma membrane of guard cells and QUAC1-expressing oocytes revealing similar voltage dependencies and activation–deactivation kinetics. In the heterologous expression system, QUAC1 was electrophysiologically characterized at increasing extra- and intracellular malate concentrations. Thereby, malate additively stimulated the voltage-dependent QUAC1 activity. In search of structural determinants of the gating process, we could not identify transmembrane domains common for voltage-sensitive channels. However, site-directed mutations and deletions at the C-terminus of QUAC1 resulted in altered voltage-dependent channel activity. Interestingly, the replacement of a single glutamate residue, which is conserved in ALMT channels from different clades, by an alanine disrupted QUAC1 activity. Together with C- and N-terminal tagging, these results indicate that the cytosolic C-terminus is involved in the voltage-dependent gating mechanism of QUAC1.
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Affiliation(s)
- Patrick Mumm
- Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, Julius-von-Sachs Platz 2, D-97082 Würzburg, Germany
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Hlavinka J, Nauš J, Fellner M. Spontaneous mutation 7B-1 in tomato impairs blue light-induced stomatal opening. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2013; 209:75-80. [PMID: 23759105 DOI: 10.1016/j.plantsci.2013.04.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 04/05/2013] [Accepted: 04/28/2013] [Indexed: 06/02/2023]
Abstract
It was reported earlier that 7B-1 mutant in tomato (Solanum lycopersicum L.), an ABA overproducer, is defective in blue light (BL) signaling leading to BL-specific resistance to abiotic and biotic stresses. In this work, we examine responses of stomata to blue, red and white lights, fusicoccin, anion channel blockers (anthracene-9-carboxylic acid; 9-AC and niflumic acid; NIF) and ABA. Our results showed that the aperture of 7B-1 stomata does not increase in BL, suggesting that 7B-1 mutation impairs an element of BL signaling pathway involved in stomatal opening. Similar stomatal responses of 7B-1 and wild type (WT) to fusicoccin or 9-AC points out that activity of H(+)-ATPase and 9-AC-sensitive anion channels per se is not likely affected by the mutation. Since 9-AC restored stomatal opening of 7B-1 in BL, it seems that 9-AC and BL could block similar type of anion channels. The stomata of both genotypes did not respond to NIF neither in darkness nor in any light conditions tested. In light, 9-AC but not NIF restored stomatal opening inhibited by ABA in WT and 7B-1. We suggest that in comparison to WT, the activity of S-type anion channels in 7B-1 is more promoted by increased ABA content, and less reduced by BL, because of the mutant resistance to BL.
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Affiliation(s)
- Jan Hlavinka
- Centre of the Region Haná for Biotechnological and Agricultural Research, Department of Biophysics, Faculty of Science, Palacký University in Olomouc, Šlechtitelů 11, Olomouc CZ-78371, Czech Republic.
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Kamal AHM, Cho K, Choi JS, Bae KH, Komatsu S, Uozumi N, Woo SH. The wheat chloroplastic proteome. J Proteomics 2013; 93:326-42. [PMID: 23563086 DOI: 10.1016/j.jprot.2013.03.009] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Revised: 03/08/2013] [Accepted: 03/11/2013] [Indexed: 11/18/2022]
Abstract
UNLABELLED With the availability of plant genome sequencing, analysis of plant proteins with mass spectrometry has become promising and admired. Determining the proteome of a cell is still a challenging assignment, which is convoluted by proteome dynamics and convolution. Chloroplast is fastidious curiosity for plant biologists due to their intricate biochemical pathways for indispensable metabolite functions. In this review, an overview on proteomic studies conducted in wheat with a special focus on subcellular proteomics of chloroplast, salt and water stress. In recent years, we and other groups have attempted to understand the photosynthesis in wheat and abiotic stress under salt imposed and water deficit during vegetative stage. Those studies provide interesting results leading to better understanding of the photosynthesis and identifying the stress-responsive proteins. Indeed, recent studies aimed at resolving the photosynthesis pathway in wheat. Proteomic analysis combining two complementary approaches such as 2-DE and shotgun methods couple to high through put mass spectrometry (LTQ-FTICR and MALDI-TOF/TOF) in order to better understand the responsible proteins in photosynthesis and abiotic stress (salt and water) in wheat chloroplast will be focused. BIOLOGICAL SIGNIFICANCE In this review we discussed the identification of the most abundant protein in wheat chloroplast and stress-responsive under salt and water stress in chloroplast of wheat seedlings, thus providing the proteomic view of the events during the development of this seedling under stress conditions. Chloroplast is fastidious curiosity for plant biologists due to their intricate biochemical pathways for indispensable metabolite functions. An overview on proteomic studies conducted in wheat with a special focus on subcellular proteomics of chloroplast, salt and water stress. We have attempted to understand the photosynthesis in wheat and abiotic stress under salt imposed and water deficit during seedling stage. Those studies provide interesting results leading to a better understanding of the photosynthesis and identifying the stress-responsive proteins. In reality, our studies aspired at resolving the photosynthesis pathway in wheat. Proteomic analysis united two complementary approaches such as Tricine SDS-PAGE and 2-DE methods couple to high through put mass spectrometry (LTQ-FTICR and MALDI-TOF/TOF) in order to better understand the responsible proteins in photosynthesis and abiotic stress (salt and water) in wheat chloroplast will be highlighted. This article is part of a Special Issue entitled: Translational Plant Proteomics.
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Affiliation(s)
- Abu Hena Mostafa Kamal
- Research Center for Integrative Cellulomics, Korea Research Institute of Bioscience and Biotechnology, Daejeon 305-806, Republic of Korea
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Laanemets K, Wang YF, Lindgren O, Wu J, Nishimura N, Lee S, Caddell D, Merilo E, Brosche M, Kilk K, Soomets U, Kangasjärvi J, Schroeder JI, Kollist H. Mutations in the SLAC1 anion channel slow stomatal opening and severely reduce K+ uptake channel activity via enhanced cytosolic [Ca2+] and increased Ca2+ sensitivity of K+ uptake channels. THE NEW PHYTOLOGIST 2013; 197:88-98. [PMID: 23126621 PMCID: PMC3508330 DOI: 10.1111/nph.12008] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Accepted: 09/17/2012] [Indexed: 05/19/2023]
Abstract
The Arabidopsis guard cell anion channel SLAC1 is essential for stomatal closure in response to various endogenous and environmental stimuli. Interestingly, here we reveal an unexpected impairment of slac1 alleles on stomatal opening. We report that mutations in SLAC1 unexpectedly slow stomatal opening induced by light, low CO(2) and elevated air humidity in intact plants and that this is caused by the severely reduced activity of inward K(+) (K(+)(in)) channels in slac1 guard cells. Expression of channels and transporters involved in stomatal opening showed small but significant reductions in transcript levels in slac1 guard cells; however, this was deemed insufficient to explain the severely impaired K(+)(in) channel activity in slac1. We further examined resting cytosolic Ca(2+) concentration ([Ca(2+)](cyt)) and K(+)(in) channel sensitivity to [Ca(2+)](cyt) in slac1. These experiments showed higher resting [Ca(2+)](cyt) in slac1 guard cells and that reducing [Ca(2+)](cyt) to < 10 nM rapidly restored the activity of K(+)(in) channels in slac1 closer to wild-type levels. These findings demonstrate an unanticipated compensatory feedback control in plant stomatal regulation, which counteracts the impaired stomatal closing response of slac1, by down-regulating stomatal opening mechanisms and implicates enhanced [Ca(2+)](cyt) sensitivity priming as a mechanistic basis for the down-regulated K(+)(in) channel activity.
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Affiliation(s)
| | - Yong-Fei Wang
- Division of Biological Sciences, Cell and Developmental Biology Section, University of California San Diego, La Jolla CA 92093-0116, USA
- National Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institute for Biological Sciences, The Chinese Academy of Sciences, Shanghai 200032, China
| | - Ove Lindgren
- Institute of Technology, University of Tartu, 50411 Tartu, Estonia
| | - Juyou Wu
- Division of Biological Sciences, Cell and Developmental Biology Section, University of California San Diego, La Jolla CA 92093-0116, USA
| | - Noriyuki Nishimura
- Division of Biological Sciences, Cell and Developmental Biology Section, University of California San Diego, La Jolla CA 92093-0116, USA
| | - Stephen Lee
- Division of Biological Sciences, Cell and Developmental Biology Section, University of California San Diego, La Jolla CA 92093-0116, USA
| | - Daniel Caddell
- Division of Biological Sciences, Cell and Developmental Biology Section, University of California San Diego, La Jolla CA 92093-0116, USA
| | - Ebe Merilo
- Institute of Technology, University of Tartu, 50411 Tartu, Estonia
| | - Mikael Brosche
- Institute of Technology, University of Tartu, 50411 Tartu, Estonia
- Division of Plant Biology, Department of Biosciences, University of Helsinki, PO Box 65, FI-00014 Helsinki, Finland
| | - Kalle Kilk
- Department of Biochemistry, University of Tartu, 50411, Tartu, Estonia
| | - Ursel Soomets
- Department of Biochemistry, University of Tartu, 50411, Tartu, Estonia
| | - Jaakko Kangasjärvi
- Division of Plant Biology, Department of Biosciences, University of Helsinki, PO Box 65, FI-00014 Helsinki, Finland
| | - Julian I. Schroeder
- Division of Biological Sciences, Cell and Developmental Biology Section, University of California San Diego, La Jolla CA 92093-0116, USA
| | - Hannes Kollist
- Institute of Technology, University of Tartu, 50411 Tartu, Estonia
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Colcombet J, Mathieu Y, Peyronnet R, Agier N, Lelièvre F, Barbier-Brygoo H, Frachisse JM. R-type anion channel activation is an essential step for ROS-dependent innate immune response in Arabidopsis suspension cells. FUNCTIONAL PLANT BIOLOGY : FPB 2009; 36:832-843. [PMID: 32688693 DOI: 10.1071/fp09096] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Accepted: 07/23/2009] [Indexed: 06/11/2023]
Abstract
Plants are constantly exposed to environmental biotic and abiotic stresses. Plants cells perceive these factors and trigger early responses followed by delayed and complex adaptation processes. Using cell suspensions of Arabidopsis thaliana (L.) as a cellular model, we investigated the role of plasma membrane anion channels in Reactive Oxygen Species (ROS) production and in cell death which occurs during non-host pathogen infection. Protoplasts derived from Arabidopsis suspension cells display two anion currents with characteristics very similar to those of the slow nitrate-permeable (S-type) and rapid sulfate-permeable (R-type) channels previously characterised in hypocotyl cells and other cell types. Using seven inhibitors, we showed that the R-type channel and ROS formation in cell cultures present similar pharmacological profiles. The efficiency of anion channel blockers to inhibit ROS production was independent of the nature of the triggering signal (osmotic stress or general elicitors of plant defence), indicating that the R-type channel represents a crossroad in the signalling pathways leading to ROS production. In a second step, we show that treatment with R-type channel blockers accelerates cell death triggered by the non-specific plant pathogen Xanthomonas campestris. Finally, we discuss the hypothesis that the R-type channel is involved in innate immune response allowing cell defence via antibacterial ROS production.
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Affiliation(s)
- Jean Colcombet
- Present address: Unité de Recherche en Génomique Végétale, 2 rue Gaston Crémieux, 91057 Evry, France
| | - Yves Mathieu
- Institut des Sciences du Végétal, CNRS UPR 2355, 22 Avenue de la Terrasse, 91198 Gif sur Yvette, France
| | - Remi Peyronnet
- Institut des Sciences du Végétal, CNRS UPR 2355, 22 Avenue de la Terrasse, 91198 Gif sur Yvette, France
| | - Nicolas Agier
- Present address: CNRS-CGM, 14 Avenue de la Terrasse, 91198 Gif sur Yvette, France
| | - Françoise Lelièvre
- Institut des Sciences du Végétal, CNRS UPR 2355, 22 Avenue de la Terrasse, 91198 Gif sur Yvette, France
| | - Hélène Barbier-Brygoo
- Institut des Sciences du Végétal, CNRS UPR 2355, 22 Avenue de la Terrasse, 91198 Gif sur Yvette, France
| | - Jean-Marie Frachisse
- Institut des Sciences du Végétal, CNRS UPR 2355, 22 Avenue de la Terrasse, 91198 Gif sur Yvette, France
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15
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Ramos AC, Lima PT, Dias PN, Kasuya MCM, Feijó JA. A pH signaling mechanism involved in the spatial distribution of calcium and anion fluxes in ectomycorrhizal roots. THE NEW PHYTOLOGIST 2009; 181:448-462. [PMID: 19121039 DOI: 10.1111/j.1469-8137.2008.02656.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Mycorrhization is a typical example of a host-pathogen symbiotic interaction where the pathogen cell biology and the host immune response coevolved several functional links. Here, the role played by ion fluxes across the root concerning nutrient uptake, osmoregulation, growth and signaling events is addressed. An ion-selective vibrating probe system was used to determine the net fluxes of protons (H(+)), calcium (Ca(2+)) and anions (A(-)) along nonmycorrhizal and ectomycorrhizal (ECM) roots of Eucalyptus globulus colonized by Pisolithus sp. These data show that, from five root zones analyzed, the main effect of fungal colonization was localized to the elongation zone. Here, strong changes in ion dynamics and rhizosphere acidification capacity were observed. Additionally, ion fluxes exhibited periodic fluctuations. To verify whether these fluctuations corresponded to sustained oscillations, continuous wavelet time spectrum analysis was applied and it was determined that H(+) and A(-) fluxes from ECM roots had longer periods than nonmycorrhizal roots. By contrast, Ca(2+) oscillations were completely abolished following fungal interaction. These results are interpreted in the light of a working model in which nutrient uptake and stimulation of growth are mediated by ECM fungi and may be pH-dependent. Furthermore, the variations detected in ECM roots for H(+) and A(-) fluxes suggest a main contribution from the plant, while the results obtained for Ca(2+) point to a significant involvement of the fungus.
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Affiliation(s)
- Alessandro C Ramos
- Instituto Gulbenkian de Ciência, Centro de Biologia do Desenvolvimento, Oeiras, 2780-901, Portugal;Depto de Microbiologia, Universidade Federal de Viçosa, Viçosa-MG, 36570-000, Brazil;Depto Biologia Vegetal, Faculdade de Ciências da Universidade de Lisboa, Lisboa, Campo Grande, 1700, Portugal
| | - Pedro T Lima
- Instituto Gulbenkian de Ciência, Centro de Biologia do Desenvolvimento, Oeiras, 2780-901, Portugal;Depto de Microbiologia, Universidade Federal de Viçosa, Viçosa-MG, 36570-000, Brazil;Depto Biologia Vegetal, Faculdade de Ciências da Universidade de Lisboa, Lisboa, Campo Grande, 1700, Portugal
| | - Pedro N Dias
- Instituto Gulbenkian de Ciência, Centro de Biologia do Desenvolvimento, Oeiras, 2780-901, Portugal;Depto de Microbiologia, Universidade Federal de Viçosa, Viçosa-MG, 36570-000, Brazil;Depto Biologia Vegetal, Faculdade de Ciências da Universidade de Lisboa, Lisboa, Campo Grande, 1700, Portugal
| | - Maria Catarina M Kasuya
- Instituto Gulbenkian de Ciência, Centro de Biologia do Desenvolvimento, Oeiras, 2780-901, Portugal;Depto de Microbiologia, Universidade Federal de Viçosa, Viçosa-MG, 36570-000, Brazil;Depto Biologia Vegetal, Faculdade de Ciências da Universidade de Lisboa, Lisboa, Campo Grande, 1700, Portugal
| | - José A Feijó
- Instituto Gulbenkian de Ciência, Centro de Biologia do Desenvolvimento, Oeiras, 2780-901, Portugal;Depto de Microbiologia, Universidade Federal de Viçosa, Viçosa-MG, 36570-000, Brazil;Depto Biologia Vegetal, Faculdade de Ciências da Universidade de Lisboa, Lisboa, Campo Grande, 1700, Portugal
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16
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Trouverie J, Vidal G, Zhang Z, Sirichandra C, Madiona K, Amiar Z, Prioul JL, Jeannette E, Rona JP, Brault M. Anion channel activation and proton pumping inhibition involved in the plasma membrane depolarization induced by ABA in Arabidopsis thaliana suspension cells are both ROS dependent. PLANT & CELL PHYSIOLOGY 2008; 49:1495-507. [PMID: 18757862 DOI: 10.1093/pcp/pcn126] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
In Arabidopsis thaliana suspension cells, ABA was previously shown to promote the activation of anion channels and the reduction of proton pumping that both contribute to the plasma membrane depolarization. These two ABA responses were shown to induce two successive [Ca(2+)](cyt) spikes. As reactive oxygen species (ROS) have emerged as components of ABA signaling pathways especially by promoting [Ca(2+)](cyt) variations, we studied whether ROS were involved in the regulation of anion channels and proton pumps activities. Here we demonstrated that ABA induced ROS production which triggered the second of the two [Ca(2+)](cyt) increases observed in response to ABA. Blocking ROS generation using diphenyleneiodonium (DPI) impaired the proton pumping reduction, the anion channel activation and the RD29A gene expression in response to ABA. Furthermore, H(2)O(2) was shown to activate anion channels and to inhibit plasma membrane proton pumping, as did ABA. However, ROS partially mimicked ABA's effects since H(2)O(2) treatment elicited anion channel activation but not the subsequent expression of the RD29A gene as did ABA. This suggests that expression of the RD29A gene in response to ABA results from the activation of multiple concomitant signaling pathways: blocking of one of them would impair gene expression whereas stimulating only one would not. We conclude that ROS are a central messenger of ABA in the signaling pathways leading to the plasma membrane depolarization induced by ABA.
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Affiliation(s)
- Jacques Trouverie
- Laboratoire d'Electrophysiologie des Membranes, EA 3514, Université Paris-Diderot, 2 place Jussieu, 75251 Paris cedex 05, France
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17
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Lee Y, Lee Y. Roles of phosphoinositides in regulation of stomatal movements. PLANT SIGNALING & BEHAVIOR 2008; 3:211-3. [PMID: 19513215 PMCID: PMC2634180 DOI: 10.4161/psb.3.4.5557] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2008] [Accepted: 11/01/2008] [Indexed: 05/04/2023]
Abstract
Guard cells sense various environmental and internal stimuli and, in response, modulate the stomatal aperture to a size optimal for growth and adaptation. Among the many factors involved in the fine regulation of stomata, we have focused our studies on the role of phosphoinositides. Our recent study published in the Plant Journal (52:803-16) provides evidence for an important role for phosphatidylinositol 4,5-bis-phosphate (PtdIns(4,5)P(2)) in inducing stomatal opening. Light induces translocation of a PtdIns(4,5)P(2)-binding protein from the cytosol to the plasma membrane and treatments that increase the intracellular PtdIns(4,5)P(2) level induce stomatal opening in the absence of light irradiation. Inhibition of anion channel activity, a negative regulator for stomatal opening, was suggested as a mechanism of PtdIns(4,5)P(2)-induced stomatal opening. We also reported that phosphatidylinositol 3-phosphate (PtdIns(3)P) and phosphatidylinositol 4-phosphate (PtdIns(4)P) regulate actin dynamics in guard cells. The effects of the phosphoinositides were specific, and were not induced by other lipids with similar structures. The roles of different interacting partners are likely to be important for these lipids to produce specific changes in guard cell activity.
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Affiliation(s)
- Yuree Lee
- POSTECH-UZH Global Research Lab; Division of Molecular Life Sciences; POSTECH; Pohang, Korea
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18
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Lang RD, Volkov AG. Solitary waves in soybean induced by localized thermal stress. PLANT SIGNALING & BEHAVIOR 2008; 3:224-8. [PMID: 19513218 PMCID: PMC2634183 DOI: 10.4161/psb.3.4.5586] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2007] [Accepted: 01/14/2007] [Indexed: 05/08/2023]
Abstract
Action potentials in higher plants are believed to be the information carriers in intercellular and intracellular communication in the presence of an environmental stressor. Plant electrophysiologists have recorded long distance electrical signaling in higher plants during the last two hundred years. Reproducing the duration, speed of propagation, and the shape of the action potential is challenging. Early measurements revealed that the speed of action potential propagation in plants is extremely slow - from 0.1 mm/s to 20 cm/s, although many faster plant responses to stress have been recorded as well. We hypothesized that this discrepancy is most likely due to the artifacts of aliasing from slow registration systems. In this study, we employ real time measurements using modern data acquisition techniques to detect ultra fast action potentials in green plants induced by localized heat stress. Thermal shock or heat stress is the most common environmental stress. Based on more sophisticated measuring techniques, we show that plants transmit solitary waves and that the speed of action potential propagation in green plants is similar to the speed of action potentials in mammalians, varying from a few meters per second up to 105 m/s. Possible pathways for electrical signal propagation in vascular plants are discussed.
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Affiliation(s)
- Ryan D Lang
- Department of Chemistry and Biochemistry; Oakwood University; Huntsville, Alabama USA
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19
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Wasilewska A, Vlad F, Sirichandra C, Redko Y, Jammes F, Valon C, Frei dit Frey N, Leung J. An update on abscisic acid signaling in plants and more... MOLECULAR PLANT 2008; 1:198-217. [PMID: 19825533 DOI: 10.1093/mp/ssm022] [Citation(s) in RCA: 243] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The mode of abscisic acid (ABA) action, and its relations to drought adaptive responses in particular, has been a captivating area of plant hormone research for much over a decade. The hormone triggers stomatal closure to limit water loss through transpiration, as well as mobilizes a battery of genes that presumably serve to protect the cells from the ensuing oxidative damage in prolonged stress. The signaling network orchestrating these various responses is, however, highly complex. This review summarizes several significant advances made within the last few years. The biosynthetic pathway of the hormone is now almost completely elucidated, with the latest identification of the ABA4 gene encoding a neoxanthin synthase, which seems essential for de novo ABA biosynthesis during water stress. This leads to the interesting question on how ABA is then delivered to perception sites. In this respect, regulated transport has attracted renewed focus by the unexpected finding of a shoot-to-root translocation of ABA during drought response, and at the cellular level, by the identification of a beta-galactosidase that releases biologically active ABA from inactive ABA-glucose ester. Surprising candidate ABA receptors were also identified in the form of the Flowering Time Control Protein A (FCA) and the Chloroplastic Magnesium Protoporphyrin-IX Chelatase H subunit (CHLH) in chloroplast-nucleus communication, both of which have been shown to bind ABA in vitro. On the other hand, the protein(s) corresponding to the physiologically detectable cell-surface ABA receptor(s) is (are) still not known with certainty. Genetic and physiological studies based on the guard cell have reinforced the central importance of reversible phosphorylation in modulating rapid ABA responses. Sucrose Non-Fermenting Related Kinases (SnRK), Calcium-Dependent Protein Kinases (CDPK), Protein Phosphatases (PP) of the 2C and 2A classes figure as prominent regulators in this single-cell model. Identifying their direct in vivo targets of regulation, which may include H(+)-ATPases, ion channels, 14-3-3 proteins and transcription factors, will logically be the next major challenge. Emerging evidence also implicates ABA as a repressor of innate immune response, as hinted by the highly similar roster of genes elicited by certain pathogens and ABA. Undoubtedly, the most astonishing revelation is that ABA is not restricted to plants and mosses, but overwhelming evidence now indicates that it also exists in metazoans ranging from the most primitive to the most advance on the evolution scale (sponges to humans). In metazoans, ABA has healing properties, and plays protective roles against both environmental and pathogen related injuries. These cross-kingdom comparisons have shed light on the surprising ancient origin of ABA and its attendant mechanisms of signal transduction.
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Affiliation(s)
- Aleksandra Wasilewska
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, UPR 2355, 1 Avenue de la Terrasse, Bât. 23, 91190 Gif-sur-Yvette, France
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20
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Lee Y, Kim YW, Jeon BW, Park KY, Suh SJ, Seo J, Kwak JM, Martinoia E, Hwang I, Lee Y. Phosphatidylinositol 4,5-bisphosphate is important for stomatal opening. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2007; 52:803-16. [PMID: 17883374 DOI: 10.1111/j.1365-313x.2007.03277.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Previously, we demonstrated that a protein that binds phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P(2)] inhibits both light-induced stomatal opening and ABA-induced stomatal closing. The latter effect is due to a reduction in free PtdIns(4,5)P(2), decreasing production of inositol 1,4,5-trisphosphate and phosphatidic acid by phospholipases C and D. However, it is less clear how PtdIns(4,5)P(2) modulates stomatal opening. We found that in response to white light irradiation, the PtdIns(4,5)P(2)-binding domain GFP:PLCdelta1PH translocated from the cytosol into the plasma membrane. This suggests that the level of PtdIns(4,5)P(2) increases at the plasma membrane upon illumination. Exogenously administered PtdIns(4,5)P(2) substituted for light stimuli, inducing stomatal opening and swelling of guard cell protoplasts. To identify PtdIns(4,5)P(2) targets we performed patch-clamp experiments, and found that anion channel activity was inhibited by PtdIns(4,5)P(2). Genetic analyses using an Arabidopsis PIP5K4 mutant further supported the role of PtdIns(4,5)P(2) in stomatal opening. The reduced stomatal opening movements exhibited by a mutant of Arabidopsis PIP5K4 (At3g56960) was countered by exogenous application of PtdIns(4,5)P(2). The phenotype of reduced stomatal opening in the pip5k4 mutant was recovered in lines complemented with the full-length PIP5K4. Together, these data suggest that PIP5K4 produces PtdIns(4,5)P(2) in irradiated guard cells, inhibiting anion channels to allow full stomatal opening.
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Affiliation(s)
- Yuree Lee
- POSTECH-VZH Global Research Lab., Division of Molecular Life Sciences, POSTECH, Pohang, 790-784, Korea.
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21
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Merlot S, Leonhardt N, Fenzi F, Valon C, Costa M, Piette L, Vavasseur A, Genty B, Boivin K, Müller A, Giraudat J, Leung J. Constitutive activation of a plasma membrane H(+)-ATPase prevents abscisic acid-mediated stomatal closure. EMBO J 2007; 26:3216-26. [PMID: 17557075 PMCID: PMC1914098 DOI: 10.1038/sj.emboj.7601750] [Citation(s) in RCA: 205] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2007] [Accepted: 05/16/2007] [Indexed: 01/16/2023] Open
Abstract
Light activates proton (H(+))-ATPases in guard cells, to drive hyperpolarization of the plasma membrane to initiate stomatal opening, allowing diffusion of ambient CO(2) to photosynthetic tissues. Light to darkness transition, high CO(2) levels and the stress hormone abscisic acid (ABA) promote stomatal closing. The overall H(+)-ATPase activity is diminished by ABA treatments, but the significance of this phenomenon in relationship to stomatal closure is still debated. We report two dominant mutations in the OPEN STOMATA2 (OST2) locus of Arabidopsis that completely abolish stomatal response to ABA, but importantly, to a much lesser extent the responses to CO(2) and darkness. The OST2 gene encodes the major plasma membrane H(+)-ATPase AHA1, and both mutations cause constitutive activity of this pump, leading to necrotic lesions. H(+)-ATPases have been traditionally assumed to be general endpoints of all signaling pathways affecting membrane polarization and transport. Our results provide evidence that AHA1 is a distinct component of an ABA-directed signaling pathway, and that dynamic downregulation of this pump during drought is an essential step in membrane depolarization to initiate stomatal closure.
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Affiliation(s)
- Sylvain Merlot
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, UPR 2355, Gif-sur-Yvette, France
| | - Nathalie Leonhardt
- CEA Cadarache, DSV, UMR 6191 CEA-CNRS, DEVM, LEMS and LEMP, St Paul les Durance Cedex, France
| | - Francesca Fenzi
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, UPR 2355, Gif-sur-Yvette, France
| | - Christiane Valon
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, UPR 2355, Gif-sur-Yvette, France
| | - Miguel Costa
- CEA Cadarache, DSV, UMR 6191 CEA-CNRS, DEVM, LEMS and LEMP, St Paul les Durance Cedex, France
| | - Laurie Piette
- CEA Cadarache, DSV, UMR 6191 CEA-CNRS, DEVM, LEMS and LEMP, St Paul les Durance Cedex, France
| | - Alain Vavasseur
- CEA Cadarache, DSV, UMR 6191 CEA-CNRS, DEVM, LEMS and LEMP, St Paul les Durance Cedex, France
| | - Bernard Genty
- CEA Cadarache, DSV, UMR 6191 CEA-CNRS, DEVM, LEMS and LEMP, St Paul les Durance Cedex, France
| | - Karine Boivin
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, UPR 2355, Gif-sur-Yvette, France
| | | | - Jérôme Giraudat
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, UPR 2355, Gif-sur-Yvette, France
| | - Jeffrey Leung
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, UPR 2355, Gif-sur-Yvette, France
- CNRS Science de la Vie, Institut des Sciences du Végétal, UPR 2355, 1 Avenue de la Terrasse Bat. 23, Gif-sur-Yvette, 91190, France. Tel.: +33 1 69 82 38 12; Fax: +33 1 69 82 36 95; E-mail:
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22
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de Angeli A, Thomine S, Frachisse JM, Ephritikhine G, Gambale F, Barbier-Brygoo H. Anion channels and transporters in plant cell membranes. FEBS Lett 2007; 581:2367-74. [PMID: 17434490 DOI: 10.1016/j.febslet.2007.04.003] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2007] [Revised: 04/01/2007] [Accepted: 04/02/2007] [Indexed: 11/29/2022]
Abstract
Anion channels/transporters appear as key players in signaling pathways leading to the adaptation of plant cells to abiotic and biotic environmental stresses, in the control of metabolism and in the maintenance of electrochemical gradients. Focusing on the most recent advances, this review aims at providing a description of the role of these channels in various physiological functions such as control of stomatal movements, plant-pathogen interaction, xylem loading, compartmentalization of metabolites and coupling with proton gradients. These functions have been demonstrated by a combination of electrophysiology, pharmacology and genetics approaches, the key issue being to identify the corresponding proteins and genes.
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Affiliation(s)
- Alexis de Angeli
- Institut des Sciences du Végétal, UPR 2355, CNRS, 1 Avenue de la Terrasse, 91198 Gif sur Yvette Cedex, France
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23
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Li S, Assmann SM, Albert R. Predicting essential components of signal transduction networks: a dynamic model of guard cell abscisic acid signaling. PLoS Biol 2007; 4:e312. [PMID: 16968132 PMCID: PMC1564158 DOI: 10.1371/journal.pbio.0040312] [Citation(s) in RCA: 304] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2006] [Accepted: 07/21/2006] [Indexed: 02/02/2023] Open
Abstract
Plants both lose water and take in carbon dioxide through microscopic stomatal pores, each of which is regulated by a surrounding pair of guard cells. During drought, the plant hormone abscisic acid (ABA) inhibits stomatal opening and promotes stomatal closure, thereby promoting water conservation. Dozens of cellular components have been identified to function in ABA regulation of guard cell volume and thus of stomatal aperture, but a dynamic description is still not available for this complex process. Here we synthesize experimental results into a consistent guard cell signal transduction network for ABA-induced stomatal closure, and develop a dynamic model of this process. Our model captures the regulation of more than 40 identified network components, and accords well with previous experimental results at both the pathway and whole-cell physiological level. By simulating gene disruptions and pharmacological interventions we find that the network is robust against a significant fraction of possible perturbations. Our analysis reveals the novel predictions that the disruption of membrane depolarizability, anion efflux, actin cytoskeleton reorganization, cytosolic pH increase, the phosphatidic acid pathway, or K(+) efflux through slowly activating K(+) channels at the plasma membrane lead to the strongest reduction in ABA responsiveness. Initial experimental analysis assessing ABA-induced stomatal closure in the presence of cytosolic pH clamp imposed by the weak acid butyrate is consistent with model prediction. Simulations of stomatal response as derived from our model provide an efficient tool for the identification of candidate manipulations that have the best chance of conferring increased drought stress tolerance and for the prioritization of future wet bench analyses. Our method can be readily applied to other biological signaling networks to identify key regulatory components in systems where quantitative information is limited.
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Affiliation(s)
- Song Li
- Biology Department, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Sarah M Assmann
- Biology Department, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Réka Albert
- Physics Department, Pennsylvania State University, University Park, Pennsylvania, United States of America
- * To whom correspondence should be addressed. E-mail:
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24
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Roberts SK. Plasma membrane anion channels in higher plants and their putative functions in roots. THE NEW PHYTOLOGIST 2006; 169:647-66. [PMID: 16441747 DOI: 10.1111/j.1469-8137.2006.01639.x] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Recent years have seen considerable progress in identifying anion channel activities in higher plant cells. This review outlines the functional properties of plasma membrane anion channels in plant cells and discusses their likely roles in root function. Plant anion channels can be grouped according to their voltage dependence and kinetics: (1) depolarization-activated anion channels which mediate either anion efflux (R and S types) or anion influx (outwardly rectifying type); (2) hyperpolarization-activated anion channels which mediate anion efflux, and (3) anion channels activated by light or membrane stretch. These types of anion channel are apparent in root cells where they may function in anion homeostasis, membrane stabilization, osmoregulation, boron tolerance and regulation of passive salt loading into the xylem vessels. In addition, roots possess anion channels exhibiting unique properties which are consistent with them having specialized functions in root physiology. Most notable are the organic anion selective channels, which are regulated by extracellular Al3+ or the phosphate status of the plant. Finally, although the molecular identities of plant anion channels remain elusive, the diverse electrophysiological properties of plant anion channels suggest that large and diverse multigene families probably encode these channels.
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Affiliation(s)
- Stephen K Roberts
- Lancaster Environment Centre, Biology Department, Lancaster University, Lancaster LA1 4YQ, UK.
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25
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Zhang Z, Ramirez J, Reboutier D, Brault M, Trouverie J, Pennarun AM, Amiar Z, Biligui B, Galagovsky L, Rona JP. Brassinosteroids regulate plasma membrane anion channels in addition to proton pumps during expansion of Arabidopsis thaliana cells. PLANT & CELL PHYSIOLOGY 2005; 46:1494-504. [PMID: 16020430 DOI: 10.1093/pcp/pci162] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Brassinosteroids (BRs) are involved in numerous physiological processes associated with plant development and especially with cell expansion. Here we report that two BRs, 28-homobrassinolide (HBL) and its direct precursor 28-homocastasterone (HCS), promote cell expansion of Arabidopsis thaliana suspension cells. We also show that cell expansions induced by HBL and HCS are correlated with the amplitude of the plasma membrane hyperpolarization they elicited. HBL, which promoted the larger cell expansion, also provoked the larger hyperpolarization. We observed that membrane hyperpolarization and cell expansion were partially inhibited by the proton pump inhibitor erythrosin B, suggesting that proton pumps were not the only ion transport system modulated by the two BRs. We used a voltage clamp approach in order to find the other ion transport systems involved in the PM hyperpolarization elicited by HBL and HCS. Interestingly, while anion currents were inhibited by both HBL and HCS, outward rectifying K+ currents were increased by HBL but inhibited by HCS. The different electrophysiological behavior shown by HBL and HCS indicates that small changes in the BR skeleton might be responsible for changes in bioactivity.
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Affiliation(s)
- Zongshen Zhang
- Laboratoire d'Electrophysiologie des Membranes, EA 3514, Université Paris 7, 2 Place Jussieu, 75251 Paris Cedex 05, France
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26
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Roelfsema MRG, Hedrich R. In the light of stomatal opening: new insights into 'the Watergate'. THE NEW PHYTOLOGIST 2005; 167:665-91. [PMID: 16101906 DOI: 10.1111/j.1469-8137.2005.01460.x] [Citation(s) in RCA: 307] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Stomata can be regarded as hydraulically driven valves in the leaf surface, which open to allow CO2 uptake and close to prevent excessive loss of water. Movement of these 'Watergates' is regulated by environmental conditions, such as light, CO2 and humidity. Guard cells can sense environmental conditions and function as motor cells within the stomatal complex. Stomatal movement results from the transport of K+ salts across the guard cell membranes. In this review, we discuss the biophysical principles and mechanisms of stomatal movement and relate these to ion transport at the plasma membrane and vacuolar membrane. Studies with isolated guard cells, combined with recordings on single guard cells in intact plants, revealed that light stimulates stomatal opening via blue light-specific and photosynthetic-active radiation-dependent pathways. In addition, guard cells sense changes in air humidity and the water status of distant tissues via the stress hormone abscisic acid (ABA). Guard cells thus provide an excellent system to study cross-talk, as multiple signaling pathways induce both short- and long-term responses in these sensory cells.
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Affiliation(s)
- M Rob G Roelfsema
- Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Würzburg University, Julius-von-Sachs-Platz 2, D-97082 Würzburg, Germany
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27
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Abstract
In this review we concentrate on guard cell metabolism and CO2 sensing. Although a matter of some controversy, it is generally accepted that the Calvin cycle plays a minor role in stomatal movements. Recent data emphasise the importance of guard cell starch degradation and of carbon import from the guard cell apoplast in promoting and maintaining stomatal opening. Chloroplast maltose and glucose transporters appear to be crucial to the export of carbon from both guard and mesophyll cells. The way guard cells sense CO2 remains an unresolved question. However, a better understanding of the cellular events downstream from CO2 sensing is emerging. We now recognise that there are common as well as unique steps in abscisic acid (ABA) and CO2 signalling pathways. For example, while ABA and CO2 both trigger increases in cytoplasmic free calcium, unlike ABA, CO2 does not promote a cytoplasmic pH change. Future advances in this area are likely to result from the increased use of techniques and resources, such as, reverse genetics, novel mutants, confocal imaging, and microarray analyses of the guard cell transcriptome.
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Affiliation(s)
- Alain Vavasseur
- CEA/Cadarache-DSV-DEVM, Laboratoire des Echanges Membranaires et Signalisation, UMR 6191 CNRS-CEA-Aix-Marseille II. 13108 St Paul Lez-Durance Cedex, France.
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28
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Qi Z, Kishigami A, Nakagawa Y, Iida H, Sokabe M. A mechanosensitive anion channel in Arabidopsis thaliana mesophyll cells. PLANT & CELL PHYSIOLOGY 2004; 45:1704-1708. [PMID: 15574846 DOI: 10.1093/pcp/pch194] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Mechanosensitive ion channels are expected to play important roles in transducing mechanical stimuli into intracellular signals during the development and morphogenesis of higher plants. We have identified a novel mechanosensitive anion channel in the protoplast of Arabidopsis thaliana mesophyll cells by using the patch-clamp technique. The channel in the outside-out patches could be activated by positive pressure in the pipette while negative pressure had no effect. The amphipathic membrane crenator trinitrophenol, which is supposed to preferentially insert in the outer leaflet of the lipid bilayer of the plasma membrane, synergized with mechanical membrane stretch to activate the channel. These results suggest that the channel activation is mediated by a convex curvature of the plasma membrane. Therefore, activation of this channel may play an important role when cell volume is increasing during cell growth or hypo-osmotic challenge, which is accompanied by membrane stretch with increasingly convex curvature.
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Affiliation(s)
- Zhi Qi
- Lab of Visual Information Processing, Centre for Brain and Cognitive Sciences, Institute of Biophysics, CAS, 15 Da Tun Road, Chaoyang District, Beijing 100101, China.
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29
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Brault M, Amiar Z, Pennarun AM, Monestiez M, Zhang Z, Cornel D, Dellis O, Knight H, Bouteau F, Rona JP. Plasma membrane depolarization induced by abscisic acid in Arabidopsis suspension cells involves reduction of proton pumping in addition to anion channel activation, which are both Ca2+ dependent. PLANT PHYSIOLOGY 2004. [PMID: 15141069 DOI: 10.1104/pp.103.039255] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
In Arabidopsis suspension cells a rapid plasma membrane depolarization is triggered by abscisic acid (ABA). Activation of anion channels was shown to be a component leading to this ABA-induced plasma membrane depolarization. Using experiments employing combined voltage clamping, continuous measurement of extracellular pH, we examined whether plasma membrane H(+)-ATPases could also be involved in the depolarization. We found that ABA causes simultaneously cell depolarization and medium alkalinization, the second effect being abolished when ABA is added in the presence of H+ pump inhibitors. Inhibition of the proton pump by ABA is thus a second component leading to the plasma membrane depolarization. The ABA-induced depolarization is therefore the result of two different processes: activation of anion channels and inhibition of H(+)-ATPases. These two processes are independent because impairing one did not suppress the depolarization. Both processes are however dependent on the [Ca2+]cyt increase induced by ABA since increase in [Ca(2+)](cyt) enhanced anion channels and impaired H(+)-ATPases.
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Affiliation(s)
- Mathias Brault
- Laboratoire d'Electrophysiologie des Membranes, EA 3514, Université Paris 7, 75251 Paris 05, France.
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30
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Brault M, Amiar Z, Pennarun AM, Monestiez M, Zhang Z, Cornel D, Dellis O, Knight H, Bouteau F, Rona JP. Plasma membrane depolarization induced by abscisic acid in Arabidopsis suspension cells involves reduction of proton pumping in addition to anion channel activation, which are both Ca2+ dependent. PLANT PHYSIOLOGY 2004; 135:231-43. [PMID: 15141069 PMCID: PMC429360 DOI: 10.1104/pp.104.039255] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2004] [Revised: 02/06/2004] [Accepted: 03/04/2004] [Indexed: 05/09/2023]
Abstract
In Arabidopsis suspension cells a rapid plasma membrane depolarization is triggered by abscisic acid (ABA). Activation of anion channels was shown to be a component leading to this ABA-induced plasma membrane depolarization. Using experiments employing combined voltage clamping, continuous measurement of extracellular pH, we examined whether plasma membrane H(+)-ATPases could also be involved in the depolarization. We found that ABA causes simultaneously cell depolarization and medium alkalinization, the second effect being abolished when ABA is added in the presence of H+ pump inhibitors. Inhibition of the proton pump by ABA is thus a second component leading to the plasma membrane depolarization. The ABA-induced depolarization is therefore the result of two different processes: activation of anion channels and inhibition of H(+)-ATPases. These two processes are independent because impairing one did not suppress the depolarization. Both processes are however dependent on the [Ca2+]cyt increase induced by ABA since increase in [Ca(2+)](cyt) enhanced anion channels and impaired H(+)-ATPases.
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Affiliation(s)
- Mathias Brault
- Laboratoire d'Electrophysiologie des Membranes, EA 3514, Université Paris 7, 75251 Paris 05, France.
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31
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Pearson GA, Serrão EA, Dring M, Schmid R. Blue- and green-light signals for gamete release in the brown alga, Silvetia compressa. Oecologia 2004; 138:193-201. [PMID: 14605987 DOI: 10.1007/s00442-003-1424-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2003] [Accepted: 10/02/2003] [Indexed: 11/25/2022]
Abstract
The intertidal brown alga Silvetia compressa releases gametes from receptacles (the reproductive tissue) rapidly upon a dark transfer (following a photosynthesis-dependent period in the light, termed potentiation). In this study, the wavelength-dependence of this process was investigated. During the potentiation period in white light (WL), gametes are not released. However, gametes were released during potentiation in blue light (BL), or in low red light/blue light (RL/BL) ratios, but not in RL alone, high RL/BL ratios, or in broadband blue-green light (B-GL) (presence of BL, but absence of RL). RL was as effective as WL for potentiation, i.e., both lead to gamete release following transfer to darkness. Rates of linear photosynthetic electron transport were similar in RL and BL. Gamete release in BL was inhibited by equal amounts of additional narrow-waveband light between the green and red regions of the spectrum, with light-induced gamete release restricted between <491 nm and 509 nm. Very little light-induced gamete release occurred between 530 nm and 650 nm. It is proposed that a BL-responsive photoreceptor is responsible for light-induced gamete release. Transfer of WL-potentiated receptacles to GL near 530 nm resulted in significant de-potentiation and reduced gamete release during a subsequent dark transfer. This effect was not seen at 509 nm or 560 nm and revealed the presence of a second photoreceptor system repressing or counteracting potentiation in the light. We propose that the restriction of gamete release to periods when irradiance is blue-shifted may constitute a depth-sensing mechanism for this intertidal alga, allowing controlled release of gametes at high tide and/or less turbid periods, thus minimizing gamete dilution, and promoting fertilization success.
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Affiliation(s)
- Gareth A Pearson
- Center for Marine Sciences, Faculdade de Ciências do Mar e do Ambiente, Universidade do Algarve, Gambelas, 8005-139 Faro, Portugal.
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32
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Mithöfer A, Fliegmann J, Daxberger A, Ebel C, Neuhaus-Url G, Bhagwat AA, Keister DL, Ebel J. Induction of H(2)O(2) synthesis by beta-glucan elicitors in soybean is independent of cytosolic calcium transients. FEBS Lett 2001; 508:191-5. [PMID: 11718714 DOI: 10.1016/s0014-5793(01)03054-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Soybean cell suspension cultures have been used to investigate the role of the elevation of the cytosolic Ca(2+) concentration in beta-glucan elicitors-induced defence responses, such as H(2)O(2) and phytoalexin production. The intracellular Ca(2+) concentration was monitored in transgenic cells expressing the Ca(2+)-sensing aequorin. Two lines of evidence showed that a transient increase of the cytosolic Ca(2+) concentration is not necessarily involved in the induction of H(2)O(2) generation: (i) a Bradyrhizobium japonicum cyclic beta-glucan induced the H(2)O(2) burst without increasing the cytosolic Ca(2+) concentration; (ii) two ion channel blockers (anthracene-9-carboxylate, A9C; 5-nitro-2-(3-phenylpropylamino)-benzoate, NPPB) could not prevent a Phytophthora soja beta-glucan elicitor-induced H(2)O(2) synthesis but did prevent a cytosolic Ca(2+) concentration increase. Moreover, A9C and NPPB inhibited P. sojae beta-glucan-elicited defence-related gene inductions as well as the inducible accumulation of phytoalexins, suggesting that the P. sojae beta-glucan-induced transient cytosolic Ca(2+) increase is not necessary for the elicitation of H(2)O(2) production but is very likely required for phytoalexin synthesis.
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33
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Kwak JM, Murata Y, Baizabal-Aguirre VM, Merrill J, Wang M, Kemper A, Hawke SD, Tallman G, Schroeder JI. Dominant negative guard cell K+ channel mutants reduce inward-rectifying K+ currents and light-induced stomatal opening in arabidopsis. PLANT PHYSIOLOGY 2001; 127:473-485. [PMID: 11598222 DOI: 10.1104/pp.010428.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Inward-rectifying potassium (K+(in)) channels in guard cells have been suggested to provide a pathway for K+ uptake into guard cells during stomatal opening. To test the proposed role of guard cell K+(in) channels in light-induced stomatal opening, transgenic Arabidopsis plants were generated that expressed dominant negative point mutations in the K+(in) channel subunit KAT1. Patch-clamp analyses with transgenic guard cells from independent lines showed that K+(in) current magnitudes were reduced by approximately 75% compared with vector-transformed controls at -180 mV, which resulted in reduction in light-induced stomatal opening by 38% to 45% compared with vector-transformed controls. Analyses of intracellular K+ content using both sodium hexanitrocobaltate (III) and elemental x-ray microanalyses showed that light-induced K+ uptake was also significantly reduced in guard cells of K+(in) channel depressor lines. These findings support the model that K+(in) channels contribute to K+ uptake during light-induced stomatal opening. Furthermore, transpirational water loss from leaves was reduced in the K+(in) channel depressor lines. Comparisons of guard cell K+(in) current magnitudes among four different transgenic lines with different K+(in) current magnitudes show the range of activities of K+(in) channels required for guard cell K+ uptake during light-induced stomatal opening.
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Affiliation(s)
- J M Kwak
- Division of Biology, Cell and Developmental Biology Section, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0116, USA
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34
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Kwak JM, Murata Y, Baizabal-Aguirre VM, Merrill J, Wang M, Kemper A, Hawke SD, Tallman G, Schroeder JI. Dominant negative guard cell K+ channel mutants reduce inward-rectifying K+ currents and light-induced stomatal opening in arabidopsis. PLANT PHYSIOLOGY 2001. [PMID: 11598222 DOI: 10.1104/pp.010428] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Inward-rectifying potassium (K+(in)) channels in guard cells have been suggested to provide a pathway for K+ uptake into guard cells during stomatal opening. To test the proposed role of guard cell K+(in) channels in light-induced stomatal opening, transgenic Arabidopsis plants were generated that expressed dominant negative point mutations in the K+(in) channel subunit KAT1. Patch-clamp analyses with transgenic guard cells from independent lines showed that K+(in) current magnitudes were reduced by approximately 75% compared with vector-transformed controls at -180 mV, which resulted in reduction in light-induced stomatal opening by 38% to 45% compared with vector-transformed controls. Analyses of intracellular K+ content using both sodium hexanitrocobaltate (III) and elemental x-ray microanalyses showed that light-induced K+ uptake was also significantly reduced in guard cells of K+(in) channel depressor lines. These findings support the model that K+(in) channels contribute to K+ uptake during light-induced stomatal opening. Furthermore, transpirational water loss from leaves was reduced in the K+(in) channel depressor lines. Comparisons of guard cell K+(in) current magnitudes among four different transgenic lines with different K+(in) current magnitudes show the range of activities of K+(in) channels required for guard cell K+ uptake during light-induced stomatal opening.
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Affiliation(s)
- J M Kwak
- Division of Biology, Cell and Developmental Biology Section, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0116, USA
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35
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Kwak JM, Murata Y, Baizabal-Aguirre VM, Merrill J, Wang M, Kemper A, Hawke SD, Tallman G, Schroeder JI. Dominant negative guard cell K+ channel mutants reduce inward-rectifying K+ currents and light-induced stomatal opening in arabidopsis. PLANT PHYSIOLOGY 2001; 127:473-485. [PMID: 11598222 DOI: 10.1104/pp.127.2.473] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Inward-rectifying potassium (K+(in)) channels in guard cells have been suggested to provide a pathway for K+ uptake into guard cells during stomatal opening. To test the proposed role of guard cell K+(in) channels in light-induced stomatal opening, transgenic Arabidopsis plants were generated that expressed dominant negative point mutations in the K+(in) channel subunit KAT1. Patch-clamp analyses with transgenic guard cells from independent lines showed that K+(in) current magnitudes were reduced by approximately 75% compared with vector-transformed controls at -180 mV, which resulted in reduction in light-induced stomatal opening by 38% to 45% compared with vector-transformed controls. Analyses of intracellular K+ content using both sodium hexanitrocobaltate (III) and elemental x-ray microanalyses showed that light-induced K+ uptake was also significantly reduced in guard cells of K+(in) channel depressor lines. These findings support the model that K+(in) channels contribute to K+ uptake during light-induced stomatal opening. Furthermore, transpirational water loss from leaves was reduced in the K+(in) channel depressor lines. Comparisons of guard cell K+(in) current magnitudes among four different transgenic lines with different K+(in) current magnitudes show the range of activities of K+(in) channels required for guard cell K+ uptake during light-induced stomatal opening.
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Affiliation(s)
- J M Kwak
- Division of Biology, Cell and Developmental Biology Section, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0116, USA
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36
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Roberts SK, Dixon GK, Fischer M, Sanders D. A novel low-affinity H +-Cl -co-transporter in yeast: characterization by patch clamp. Mycologia 2001. [DOI: 10.1080/00275514.2001.12063194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Stephen K. Roberts
- Department of Biology, Institute of Environmental and Natural Sciences, Lancaster University, Lancaster LA1 4YQ, United Kingdom
| | - Graham K. Dixon
- Zeneca Pharmaceuticals, Mereside, Alderley Park, Macclesfield, Cheshire, SK10 4TG
| | - Marc Fischer
- The Plant Laboratory, Department of Biology, University of York, PO Box 373, York, YO10 5YW
| | - Dale Sanders
- The Plant Laboratory, Department of Biology, University of York, PO Box 373, York, YO10 5YW
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37
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Leonhardt N, Bazin I, Richaud P, Marin E, Vavasseur A, Forestier C. Antibodies to the CFTR modulate the turgor pressure of guard cell protoplasts via slow anion channels. FEBS Lett 2001; 494:15-8. [PMID: 11297726 DOI: 10.1016/s0014-5793(01)02289-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The plasma membrane guard cell slow anion channel is a key element at the basis of water loss control in plants allowing prolonged osmolite efflux necessary for stomatal closure. This channel has been extensively studied by electrophysiological approaches but its molecular identification is still lacking. Recently, we described that this channel was sharing some similarities with the mammalian ATP-binding cassette protein, cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel [Leonhardt, N. et al. (1999) Plant Cell 11, 1141-1151]. Here, using the patch-clamp technique and a bioassay, consisting in the observation of the change in guard cell protoplasts volume, we demonstrated that a functional antibody raised against the mammalian CFTR prevented ABA-induced guard cell protoplasts shrinking and partially inhibited the slow anion current. Moreover, this antibody immunoprecipitated a polypeptide from guard cell protein extracts and immunolabeled stomata in Vicia faba leaf sections. These results indicate that the guard cell slow anion channel is, or is closely controlled by a polypeptide, exhibiting one epitope shared with the mammalian CFTR.
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Affiliation(s)
- N Leonhardt
- CEA Cadarache, Direction des Sciences du Vivant, Département d'Ecophysiologie Végétale et de Microbiologie, Laboratoire des Echanges Membranaires et Signalisation, UMR 6000 CNRS-CEA, P.O. Box 1, F-13108 Cedex, St Paul-lez-Durance, France
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38
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Barbier-Brygoo H, Vinauger M, Colcombet J, Ephritikhine G, Frachisse J, Maurel C. Anion channels in higher plants: functional characterization, molecular structure and physiological role. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1465:199-218. [PMID: 10748255 DOI: 10.1016/s0005-2736(00)00139-5] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Anion channels are well documented in various tissues, cell types and membranes of algae and higher plants, and current evidence supports their central role in cell signaling, osmoregulation, plant nutrition and metabolism. It is the aim of this review to illustrate through a few selected examples the variety of anion channels operating in plant cells and some of their regulation properties and unique physiological functions. In contrast, information on the molecular structure of plant anion channels has only recently started to emerge. Only a few genes coding for putative plant anion channels from the large chloride channel (CLC) family have been isolated, and current molecular data on these plant CLCs are presented and discussed. A major challenge remains to identify the genes encoding the various anion channels described so far in plant cells. Future prospects along this line are briefly outlined, as well as recent advances based on the use of knockout mutants in the model plant Arabidopsis thaliana to explore the physiological functions of anion channels in planta.
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Affiliation(s)
- H Barbier-Brygoo
- Institut des Sciences Végétales, Unité Propre de Recherche 40, Centre National de la Recherche Scientifique, Avenue de la Terrasse, 91198, Gif-sur-Yvette, France.
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39
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Li J, Wang XQ, Watson MB, Assmann SM. Regulation of abscisic acid-induced stomatal closure and anion channels by guard cell AAPK kinase. Science 2000; 287:300-3. [PMID: 10634783 DOI: 10.1126/science.287.5451.300] [Citation(s) in RCA: 279] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Abscisic acid (ABA) stimulates stomatal closure and thus supports water conservation by plants during drought. Mass spectrometry-generated peptide sequence information was used to clone a Vicia faba complementary DNA, AAPK, encoding a guard cell-specific ABA-activated serine-threonine protein kinase (AAPK). Expression in transformed guard cells of AAPK altered by one amino acid (lysine 43 to alanine 43) renders stomata insensitive to ABA-induced closure by eliminating ABA activation of plasma membrane anion channels. This information should allow cell-specific, targeted biotechnological manipulation of crop water status.
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Affiliation(s)
- J Li
- Department of Biology, The Pennsylvania State University, 208 Mueller Laboratory, University Park, PA 16802, USA
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40
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Torsethaugen G, Pell EJ, Assmann SM. Ozone inhibits guard cell K+ channels implicated in stomatal opening. Proc Natl Acad Sci U S A 1999; 96:13577-82. [PMID: 10557363 PMCID: PMC23990 DOI: 10.1073/pnas.96.23.13577] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ozone (O3) deleteriously affects organisms ranging from humans to crop plants, yet little is understood regarding the underlying mechanisms. In plants, O3 decreases CO2 assimilation, but whether this could result from direct O3 action on guard cells remained unknown. Potassium flux causes osmotically driven changes in guard cell volume that regulate apertures of associated microscopic pores through which CO2 is supplied to the photosynthetic mesophyll tissue. We show in Vicia faba that O3 inhibits (i) guard cell K+ channels that mediate K+ uptake that drives stomatal opening; (ii) stomatal opening in isolated epidermes; and (iii) stomatal opening in leaves, such that CO2 assimilation is reduced without direct effects of O3 on photosynthetic capacity. Direct O3 effects on guard cells may have ecological and agronomic implications for plant productivity and for response to other environmental stressors including drought.
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Affiliation(s)
- G Torsethaugen
- Environmental Resources Research Institute, Pennsylvania State University, University Park, PA 16802, USA
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41
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Kuriyama. Loss of Tonoplast Integrity Programmed in Tracheary Element Differentiation. PLANT PHYSIOLOGY 1999; 121:763-774. [PMID: 10557224 PMCID: PMC59438 DOI: 10.1104/pp.121.3.763] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/1999] [Accepted: 08/04/1999] [Indexed: 05/18/2023]
Abstract
A tracheary element (TE) is a typical example of a cell type that undergoes programmed cell death in the developmental processes of vascular plants. The loss of the selective permeability of the tonoplast, which corresponds to tonoplast disintegration, occurred after the cells commenced secondary wall thickening and played a pivotal role in the programmed cell death of TEs in a zinnia (Zinnia elegans L.) cell culture. A search for events specifically associated with the TE vacuole provided an important clue to the understanding of the cell death mechanism. The transport of fluorescein, a fluorescent organic anion, across the tonoplast declined drastically in differentiating TEs. The capacity of the vacuole to accumulate the probe was also impaired. Treatment with probenecid, an inhibitor of organic anion transport, caused rapid cell death of TEs and led to the ultimate disruption of the vacuole even in other types of cultured cells. These changes in vacuolar properties during TE development were suppressed by cycloheximide. Specific mRNA accumulation in cells cultured in a TE differentiation-inductive condition was abolished by probenecid. These results suggest that a change in vacuolar membrane permeability promotes programmed cell death in TEs.
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Affiliation(s)
- Kuriyama
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Tokyo 113, Japan
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42
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Leonhardt N, Vavasseur A, Forestier C. ATP binding cassette modulators control abscisic acid-regulated slow anion channels in guard cells. THE PLANT CELL 1999; 11:1141-52. [PMID: 10368184 PMCID: PMC144242 DOI: 10.1105/tpc.11.6.1141] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
In animal cells, ATP binding cassette (ABC) proteins are a large family of transporters that includes the sulfonylurea receptor and the cystic fibrosis transmembrane conductance regulator (CFTR). These two ABC proteins possess an ion channel activity and bind specific sulfonylureas, such as glibenclamide, but homologs have not been identified in plant cells. We recently have shown that there is an ABC protein in guard cells that is involved in the control of stomatal movements and guard cell outward K+ current. Because the CFTR, a chloride channel, is sensitive to glibenclamide and able to interact with K+ channels, we investigated its presence in guard cells. Potent CFTR inhibitors, such as glibenclamide and diphenylamine-2-carboxylic acid, triggered stomatal opening in darkness. The guard cell protoplast slow anion current that was recorded using the whole-cell patch-clamp technique was inhibited rapidly by glibenclamide in a dose-dependent manner; the concentration producing half-maximum inhibition was at 3 &mgr;M. Potassium channel openers, which bind to and act through the sulfonylurea receptor in animal cells, completely suppressed the stomatal opening induced by glibenclamide and recovered the glibenclamide-inhibited slow anion current. Abscisic acid is known to regulate slow anion channels and in our study was able to relieve glibenclamide inhibition of slow anion current. Moreover, in epidermal strip bioassays, the stomatal closure triggered by Ca2+ or abscisic acid was reversed by glibenclamide. These results suggest that the slow anion channel is an ABC protein or is tightly controlled by such a protein that interacts with the abscisic acid signal transduction pathway in guard cells.
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Affiliation(s)
- N Leonhardt
- Commissariat a l'Energie Atomique Cadarache, Direction des Sciences du Vivant, Departement d'Ecophysiologie Vegetale et Microbiologie, Laboratoire des Echanges Membranaires et Signalisation, BP1-F13108, St. Paul-lez-Durance, France
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43
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Assmann S, Armstrong F. Hormonal regulation of ion transporters: the guard cell system. BIOCHEMISTRY AND MOLECULAR BIOLOGY OF PLANT HORMONES 1999. [DOI: 10.1016/s0167-7306(08)60495-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Cessna SG, Chandra S, Low PS. Hypo-osmotic shock of tobacco cells stimulates Ca2+ fluxes deriving first from external and then internal Ca2+ stores. J Biol Chem 1998; 273:27286-91. [PMID: 9765253 DOI: 10.1074/jbc.273.42.27286] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hypo-osmotic shock of aequorin-transformed tobacco cells induces a biphasic cytosolic Ca2+ influx. Because both phases of Ca2+ entry are readily blocked by Ca2+ channel inhibitors, we conclude that the Ca2+ transients are mediated by Ca2+ channels. Evidence that the first but not second Ca2+ transient derives from external Ca2+ stores is that the first but not second influx is (i) eliminated by membrane-impermeable Ca2+ chelators, (ii) enlarged by supplementation of the medium with excess Ca2+, and (iii) reduced by the addition of competitive cations such as Mg2+ and Mn2+. Furthermore, entry of 45Ca during osmotic shock is prevented by inhibitors of the first but not second phase of Ca2+ entry. Evidence that the second wave of Ca2+ influx stems from release of intracellular Ca2+ is based on the above data plus observations that probable modulators of intracellular Ca2+ channels selectively block this phase of Ca2+ influx. Finally, a mechanism of communication between the two Ca2+ release pathways has become apparent, since perturbations that elevate or reduce the first Ca2+ transient lead to a compensating diminution/elevation of the second and vice versa. These data thus suggest that osmotic shock leads to the sequential opening of extracellular followed by intracellular Ca2+ stores and that these Ca2+ release pathways are internally compensated.
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Affiliation(s)
- S G Cessna
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-1393, USA
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Pei ZM, Ghassemian M, Kwak CM, McCourt P, Schroeder JI. Role of farnesyltransferase in ABA regulation of guard cell anion channels and plant water loss. Science 1998; 282:287-90. [PMID: 9765153 DOI: 10.1126/science.282.5387.287] [Citation(s) in RCA: 308] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Desiccation of plants during drought can be detrimental to agricultural production. The phytohormone abscisic acid (ABA) reduces water loss by triggering stomatal pore closure in leaves, a process requiring ion-channel modulation by cytoplasmic proteins. Deletion of the Arabidopsis farnesyltransferase gene ERA1 or application of farnesyltransferase inhibitors resulted in ABA hypersensitivity of guard cell anion-channel activation and of stomatal closing. ERA1 was expressed in guard cells. Double-mutant analyses of era1 with the ABA-insensitive mutants abi1 and abi2 showed that era1 suppresses the ABA-insensitive phenotypes. Moreover, era1 plants exhibited a reduction in transpirational water loss during drought treatment.
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Affiliation(s)
- Z M Pei
- Department of Biology and Center for Molecular Genetics, University of California, San Diego, La Jolla, CA 92093-0116, USA
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Pearson GA. A model for signal transduction during gamete release in the fucoid alga pelvetia compressa. PLANT PHYSIOLOGY 1998; 118:305-13. [PMID: 9733550 PMCID: PMC34869 DOI: 10.1104/pp.118.1.305] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Fucoid algae release gametes into seawater following an inductive light period (potentiation), and gamete expulsion from potentiated receptacles of Pelvetia compressa began about 2 min after a light-to-dark transition. Agitation of the medium reversed potentiation, with an exponential time course completed in about 3 h. Light regulated two signaling pathways during potentiation and gamete expulsion: a photosynthetic pathway and a photosynthesis-independent pathway in which red light was active but blue light was not. Uptake of K+ appears to have an important role in potentiation, because a 50% inhibition of potentiation occurred in the presence of the tetraethylammonium ion, a K+-channel blocker. A central role of anion channels in the maintenance of potentiation is suggested by the premature release of gametes in the light when receptacles were incubated with inhibitors of slow-type anion channels. An inhibitor of tyrosine kinases, tyrphostin A63, also inhibited potentiation. A model for gamete release from P. compressa is presented that proposes that illumination results in the accumulation of ions (e.g. K+) throughout the cells of the receptacle during potentiation, which then move into the extracellular matrix during gamete expulsion to generate osmomechanical force, resulting in gamete release.
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Affiliation(s)
- GA Pearson
- Department of Plant Biology and Pathology, University of Maine, Orono, Maine 04469-5722, USA
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Johannes, Crofts, Sanders. Control of Cl- efflux in chara corallina by cytosolic pH, free ca2+, and phosphorylation indicates a role of plasma membrane anion channels in cytosolic pH regulation. PLANT PHYSIOLOGY 1998; 118:173-81. [PMID: 9733536 PMCID: PMC34853 DOI: 10.1104/pp.118.1.173] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/1998] [Accepted: 05/25/1998] [Indexed: 05/18/2023]
Abstract
Enhanced Cl- efflux during acidosis in plants is thought to play a role in cytosolic pH (pHc) homeostasis by short-circuiting the current produced by the electrogenic H+ pump, thereby facilitating enhanced H+ efflux from the cytosol. Using an intracellular perfusion technique, which enables experimental control of medium composition at the cytosolic surface of the plasma membrane of charophyte algae (Chara corallina), we show that lowered pHc activates Cl- efflux via two mechanisms. The first is a direct effect of pHc on Cl- efflux; the second mechanism comprises a pHc-induced increase in affinity for cytosolic free Ca2+ ([Ca2+]c), which also activates Cl- efflux. Cl- efflux was controlled by phosphorylation/dephosphorylation events, which override the responses to both pHc and [Ca2+]c. Whereas phosphorylation (perfusion with the catalytic subunit of protein kinase A in the presence of ATP) resulted in a complete inhibition of Cl- efflux, dephosphorylation (perfusion with alkaline phosphatase) arrested Cl- efflux at 60% of the maximal level in a manner that was both pHc and [Ca2+]c independent. These findings imply that plasma membrane anion channels play a central role in pHc regulation in plants, in addition to their established roles in turgor/volume regulation and signal transduction.
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Affiliation(s)
- Johannes
- The Plant Laboratory, Biology Department, University of York, P.O. Box 373, York YO1 5YW, United Kingdom
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48
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Abstract
The plant hormone abscisic acid (ABA) plays a major role in seed maturation and germination, as well as in adaptation to abiotic environmental stresses. ABA promotes stomatal closure by rapidly altering ion fluxes in guard cells. Other ABA actions involve modifications of gene expression, and the analysis of ABA-responsive promoters has revealed a diversity of potential cis-acting regulatory elements. The nature of the ABA receptor(s) remains unknown. In contrast, combined biophysical, genetic, and molecular approaches have led to considerable progress in the characterization of more downstream signaling elements. In particular, substantial evidence points to the importance of reversible protein phosphorylation and modifications of cytosolic calcium levels and pH as intermediates in ABA signal transduction. Exciting advances are being made in reassembling individual components into minimal ABA signaling cascades at the single-cell level.
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Affiliation(s)
- Jeffrey Leung
- Institut des Sciences Vegetales, Unite Propre de Recherche 40, Centre National de la Recherche Scientifique, 1 Avenue de la Terrasse, 91190 Gif-sur-Yvette, France; e-mail:
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Schwarz M, Schroeder JI. Abscisic acid maintains S-type anion channel activity in ATP-depleted Vicia faba guard cells. FEBS Lett 1998; 428:177-82. [PMID: 9654130 DOI: 10.1016/s0014-5793(98)00526-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The plant hormone abscisic acid (ABA) regulates important developmental and stress responses. Recent data show that ABA activates phosphorylation events, but whether dephosphorylation events are post-translationally regulated by ABA or whether these are constitutive remains unknown. Slow anion channels in the plasma membrane of guard cells have been proposed to play an important role during ABA-induced stomatal closing. Anion channels are deactivated by removal of cytosolic ATP. However, when guard cells were treated with ABA and depleted of ATP, anion currents remained active. Subsequent removal of extracellular ABA caused deactivation of currents. Deactivation of currents was reversed by reintroduction of cytosolic MgATP. These data show that anion channels are regulated by ABA even in the absence of cytosolic ATP required for kinase-induced phosphorylation events and that anion channel activity is maintained by ABA under conditions that favor dephosphorylation-induced deactivation. Furthermore, channel activation proceeded at high ATP concentrations with nanomolar cytosolic Ca2+ showing a Ca2+-independent final step in anion channel activation.
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Affiliation(s)
- M Schwarz
- Department of Biology and Center for Molecular Genetics, University of California, San Diego, La Jolla 92093-0116, USA
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Papernik LA, Kochian LV. Possible Involvement of Al-Induced Electrical Signals in Al Tolerance in Wheat. PLANT PHYSIOLOGY 1997; 115:657-667. [PMID: 12223834 PMCID: PMC158526 DOI: 10.1104/pp.115.2.657] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The relationship between Al-induced depolarization of root-cell transmembrane electrical potentials (Em) and Al tolerance in wheat (Triticum aestivum L.) was investigated. Al exposure induced depolarizations of Em in the Al-tolerant wheat cultivars Atlas and ET3, but not in the Al-sensitive wheat cultivars Scout and ES3. The depolarizations of Em occured in root cap cells and as far back as 10 mm from the root tip. The depolarization was specific to Al3+; no depolarization was observed when roots were exposed to the rhizotoxic trivalent cation La3+. The Al-induced depolarization occurred in the presence of anion-channel antagonists that blocked the release of malate, indicating that the depolarization is not due to the electrogenic efflux of malate2-. K+-induced depolarizations in the root cap were of the same magnitude as Al-induced depolarizations, but did not trigger malate release, indicating that Al-induced depolarization of root cap cell membrane potentials is probably linked to, but is not sufficient to trigger, malate release.
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Affiliation(s)
- L. A. Papernik
- United States Plant, Soil, and Nutrition Laboratory, United States Department of Agriculture-Agricultural Research Service, Cornell University, Ithaca, New York 14853
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