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Checchetto V, Teardo E, Carraretto L, Leanza L, Szabo I. Physiology of intracellular potassium channels: A unifying role as mediators of counterion fluxes? BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:1258-1266. [PMID: 26970213 DOI: 10.1016/j.bbabio.2016.03.011] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2016] [Revised: 03/06/2016] [Accepted: 03/07/2016] [Indexed: 12/28/2022]
Abstract
Plasma membrane potassium channels importantly contribute to maintain ion homeostasis across the cell membrane. The view is emerging that also those residing in intracellular membranes play pivotal roles for the coordination of correct cell function. In this review we critically discuss our current understanding of the nature and physiological tasks of potassium channels in organelle membranes in both animal and plant cells, with a special emphasis on their function in the regulation of photosynthesis and mitochondrial respiration. In addition, the emerging role of potassium channels in the nuclear membranes in regulating transcription will be discussed. The possible functions of endoplasmic reticulum-, lysosome- and plant vacuolar membrane-located channels are also referred to. Altogether, experimental evidence obtained with distinct channels in different membrane systems points to a possible unifying function of most intracellular potassium channels in counterbalancing the movement of other ions including protons and calcium and modulating membrane potential, thereby fine-tuning crucial cellular processes. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-7, 2016', edited by Prof. Paolo Bernardi.
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Affiliation(s)
- Vanessa Checchetto
- Department of Biology, University of Padova, Viale G. Colombo 3, Padova 35131, Italy; Department of Biomedical Sciences, University of Padova, Viale G. Colombo 3, Padova 35131 Italy
| | - Enrico Teardo
- Department of Biology, University of Padova, Viale G. Colombo 3, Padova 35131, Italy
| | - Luca Carraretto
- Department of Biology, University of Padova, Viale G. Colombo 3, Padova 35131, Italy
| | - Luigi Leanza
- Department of Biology, University of Padova, Viale G. Colombo 3, Padova 35131, Italy
| | - Ildiko Szabo
- Department of Biology, University of Padova, Viale G. Colombo 3, Padova 35131, Italy; CNR Institute of Neuroscience, University of Padova, Viale G. Colombo 3, Padova 35131, Italy.
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Carraretto L, Teardo E, Checchetto V, Finazzi G, Uozumi N, Szabo I. Ion Channels in Plant Bioenergetic Organelles, Chloroplasts and Mitochondria: From Molecular Identification to Function. MOLECULAR PLANT 2016; 9:371-395. [PMID: 26751960 DOI: 10.1016/j.molp.2015.12.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 11/22/2015] [Accepted: 12/01/2015] [Indexed: 06/05/2023]
Abstract
Recent technical advances in electrophysiological measurements, organelle-targeted fluorescence imaging, and organelle proteomics have pushed the research of ion transport a step forward in the case of the plant bioenergetic organelles, chloroplasts and mitochondria, leading to the molecular identification and functional characterization of several ion transport systems in recent years. Here we focus on channels that mediate relatively high-rate ion and water flux and summarize the current knowledge in this field, focusing on targeting mechanisms, proteomics, electrophysiology, and physiological function. In addition, since chloroplasts evolved from a cyanobacterial ancestor, we give an overview of the information available about cyanobacterial ion channels and discuss the evolutionary origin of chloroplast channels. The recent molecular identification of some of these ion channels allowed their physiological functions to be studied using genetically modified Arabidopsis plants and cyanobacteria. The view is emerging that alteration of chloroplast and mitochondrial ion homeostasis leads to organelle dysfunction, which in turn significantly affects the energy metabolism of the whole organism. Clear-cut identification of genes encoding for channels in these organelles, however, remains a major challenge in this rapidly developing field. Multiple strategies including bioinformatics, cell biology, electrophysiology, use of organelle-targeted ion-sensitive probes, genetics, and identification of signals eliciting specific ion fluxes across organelle membranes should provide a better understanding of the physiological role of organellar channels and their contribution to signaling pathways in plants in the future.
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Affiliation(s)
- Luca Carraretto
- Department of Biology, University of Padova, Padova 35121, Italy
| | - Enrico Teardo
- Department of Biology, University of Padova, Padova 35121, Italy; CNR Institute of Neuroscience, University of Padova, Padova 35121, Italy
| | | | - Giovanni Finazzi
- UMR 5168 Laboratoire de Physiologie Cellulaire Végétale (LPCV) CNRS/ UJF / INRA / CEA, Institut de Recherches en Technologies et Sciences pour le Vivant (iRTSV), CEA Grenoble, 38054 Grenoble, France.
| | - Nobuyuki Uozumi
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai 980-8579, Japan.
| | - Ildiko Szabo
- Department of Biology, University of Padova, Padova 35121, Italy; CNR Institute of Neuroscience, University of Padova, Padova 35121, Italy.
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Trono D, Laus MN, Soccio M, Alfarano M, Pastore D. Modulation of Potassium Channel Activity in the Balance of ROS and ATP Production by Durum Wheat Mitochondria-An Amazing Defense Tool Against Hyperosmotic Stress. FRONTIERS IN PLANT SCIENCE 2015; 6:1072. [PMID: 26648958 PMCID: PMC4664611 DOI: 10.3389/fpls.2015.01072] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 11/16/2015] [Indexed: 05/03/2023]
Abstract
In plants, the existence of a mitochondrial potassium channel was firstly demonstrated about 15 years ago in durum wheat as an ATP-dependent potassium channel (PmitoKATP). Since then, both properties of the original PmitoKATP and occurrence of different mitochondrial potassium channels in a number of plant species (monocotyledonous and dicotyledonous) and tissues/organs (etiolated and green) have been shown. Here, an overview of the current knowledge is reported; in particular, the issue of PmitoKATP physiological modulation is addressed. Similarities and differences with other potassium channels, as well as possible cross-regulation with other mitochondrial proteins (Plant Uncoupling Protein, Alternative Oxidase, Plant Inner Membrane Anion Channel) are also described. PmitoKATP is inhibited by ATP and activated by superoxide anion, as well as by free fatty acids (FFAs) and acyl-CoAs. Interestingly, channel activation increases electrophoretic potassium uptake across the inner membrane toward the matrix, so collapsing membrane potential (ΔΨ), the main component of the protonmotive force (Δp) in plant mitochondria; moreover, cooperation between PmitoKATP and the K(+)/H(+) antiporter allows a potassium cycle able to dissipate also ΔpH. Interestingly, ΔΨ collapse matches with an active control of mitochondrial reactive oxygen species (ROS) production. Fully open channel is able to lower superoxide anion up to 35-fold compared to a condition of ATP-inhibited channel. On the other hand, ΔΨ collapse by PmitoKATP was unexpectedly found to not affect ATP synthesis via oxidative phosphorylation. This may probably occur by means of a controlled collapse due to ATP inhibition of PmitoKATP; this brake to the channel activity may allow a loss of the bulk phase Δp, but may preserve a non-classically detectable localized driving force for ATP synthesis. This ability may become crucial under environmental/oxidative stress. In particular, under moderate hyperosmotic stress (mannitol or NaCl), PmitoKATP was found to be activated by ROS, so inhibiting further large-scale ROS production according to a feedback mechanism; moreover, a stress-activated phospholipase A2 may generate FFAs, further activating the channel. In conclusion, a main property of PmitoKATP is the ability to keep in balance the control of harmful ROS with the mitochondrial/cellular bioenergetics, thus preserving ATP for energetic needs of cell defense under stress.
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Affiliation(s)
- Daniela Trono
- Consiglio per la Ricerca in Agricoltura e l’Analisi dell’Economia Agraria, Centro di Ricerca per la Cerealicoltura, Foggia, Italy
| | - Maura N. Laus
- Dipartimento di Scienze Agrarie, degli Alimenti e dell’Ambiente, Università di Foggia, Foggia, Italy
| | - Mario Soccio
- Dipartimento di Scienze Agrarie, degli Alimenti e dell’Ambiente, Università di Foggia, Foggia, Italy
| | - Michela Alfarano
- Dipartimento di Scienze Agrarie, degli Alimenti e dell’Ambiente, Università di Foggia, Foggia, Italy
| | - Donato Pastore
- Dipartimento di Scienze Agrarie, degli Alimenti e dell’Ambiente, Università di Foggia, Foggia, Italy
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Fu J, Sun Y, Chu X, Xu Y, Hu T. Exogenous 5-aminolevulenic acid promotes seed germination in Elymus nutans against oxidative damage induced by cold stress. PLoS One 2014; 9:e107152. [PMID: 25207651 PMCID: PMC4160216 DOI: 10.1371/journal.pone.0107152] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2014] [Accepted: 08/10/2014] [Indexed: 11/18/2022] Open
Abstract
The protective effects of 5-aminolevulenic acid (ALA) on germination of Elymus nutans Griseb. seeds under cold stress were investigated. Seeds of E. nutans (Damxung, DX and Zhengdao, ZD) were pre-soaked with various concentrations (0, 0.1, 0.5, 1, 5, 10 and 25 mg l−1) of ALA for 24 h before germination under cold stress (5°C). Seeds of ZD were more susceptible to cold stress than DX seeds. Both seeds treated with ALA at low concentrations (0.1–1 mg l−1) had higher final germination percentage (FGP) and dry weight at 5°C than non-ALA-treated seeds, whereas exposure to higher ALA concentrations (5–25 mg l−1) brought about a dose dependent decrease. The highest FGP and dry weight of germinating seeds were obtained from seeds pre-soaked with 1 mg l−1 ALA. After 5 d of cold stress, pretreatment with ALA provided significant protection against cold stress in the germinating seeds, significantly enhancing seed respiration rate and ATP synthesis. ALA pre-treatment also increased reduced glutathione (GSH), ascorbic acid (AsA), total glutathione, and total ascorbate concentrations, and the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR), whereas decreased the contents of malondialdehyde (MDA) and hydrogen peroxide (H2O2), and superoxide radical (O2•−) release in both germinating seeds under cold stress. In addition, application of ALA increased H+-ATPase activity and endogenous ALA concentration compared with cold stress alone. Results indicate that ALA considered as an endogenous plant growth regulator could effectively protect E. nutans seeds from cold-induced oxidative damage during germination without any adverse effect.
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Affiliation(s)
- Juanjuan Fu
- Department of Grassland Science, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi Province, P. R. China
| | - Yongfang Sun
- Department of Grassland Science, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi Province, P. R. China
| | - Xitong Chu
- Department of Grassland Science, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi Province, P. R. China
| | - Yuefei Xu
- Department of Grassland Science, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi Province, P. R. China
- * E-mail: (YX); (TH)
| | - Tianming Hu
- Department of Grassland Science, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi Province, P. R. China
- * E-mail: (YX); (TH)
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Fercha A, Capriotti AL, Caruso G, Cavaliere C, Samperi R, Stampachiacchiere S, Laganà A. Comparative analysis of metabolic proteome variation in ascorbate-primed and unprimed wheat seeds during germination under salt stress. J Proteomics 2014; 108:238-57. [PMID: 24859728 DOI: 10.1016/j.jprot.2014.04.040] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Revised: 04/11/2014] [Accepted: 04/26/2014] [Indexed: 12/01/2022]
Abstract
UNLABELLED Seed priming with ascorbic acid improves salt tolerance in durum wheat. For understanding the potential mechanisms underlying this priming effect a gel-free shotgun proteomic analysis was performed comparing unprimed to ascorbate-primed wheat seed during germination under saline and non-saline conditions. Since seed germination is the result of interplay or cross-talk between embryo and embryo-surrounding tissues, we studied the variation of metabolic proteome in both tissues separately. 167 of 697 identified and 69 of 471 identified proteins increase or decrease in abundance significantly in response to priming and/or salinity compared to untreated, unstressed control in embryo and embryo-surrounding tissues, respectively. In untreated wheat embryo salt stress was accompanied by change in 129 proteins, most of which are belonging to metabolism, energy, disease/defense, protein destination and storage categories. Ascorbate pretreatment prevents and counteracts the effects of salinity upon most of these proteins and changes specifically the abundance of 35 others proteins, most of which are involved in metabolism, protein destination and storage categories. Hierarchical clustering analysis revealed three and two major clusters of protein expression in embryo and embryo-surrounding tissues, respectively. This study opens promising new avenues to understand priming-induced salt tolerance in plants. BIOLOGICAL SIGNIFICANCE To clearly understand how ascorbate-priming enhance the salt tolerance of durum wheat during germination, we performed for the first time a comparative shotgun proteomic analysis between unprimed and ascorbate-primed wheat seeds during germination under saline and non-saline conditions. Furthermore, since seed germination is the result of interplay or cross-talk between embryo and embryo-surrounding tissues we analyzed the variation of metabolic proteome in both tissues separately. 1168 proteins exhibiting greater molecular weight diversity (ranging from 5 to 258kDa) were identified. Among them, 167 and 69 proteins were increased or decreased in abundance significantly by priming and/or salinity as compared to control, in embryo and embryo-surrounding tissues respectively. Ascorbate pretreatment alleviates the effects of salinity upon most of these proteins, particularly those involved in metabolism, energy, disease/defense, protein destination and storage functions. Hierarchical clustering analysis revealed three and two major clusters of protein accumulation in embryo and embryo-surrounding tissues, respectively. These results may provide new avenues for understanding and advancing priming-induced salt tolerance in crop plants.
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Affiliation(s)
- Azzedine Fercha
- Department of Biology, University of Abbès Laghrour Khenchela, 40000 Khenchela, Algeria; Department of Biology, University of Mentouri Constantine, 25000 Constantine, Algeria
| | - Anna Laura Capriotti
- Department of Chemistry, Sapienza Università di Roma, Piazzale Aldo Moro 5, 00185 Rome, Italy.
| | - Giuseppe Caruso
- Department of Chemistry, Sapienza Università di Roma, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Chiara Cavaliere
- Department of Chemistry, Sapienza Università di Roma, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | - Roberto Samperi
- Department of Chemistry, Sapienza Università di Roma, Piazzale Aldo Moro 5, 00185 Rome, Italy
| | | | - Aldo Laganà
- Department of Chemistry, Sapienza Università di Roma, Piazzale Aldo Moro 5, 00185 Rome, Italy
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Trono D, Laus MN, Soccio M, Pastore D. Transport pathways--proton motive force interrelationship in durum wheat mitochondria. Int J Mol Sci 2014; 15:8186-215. [PMID: 24821541 PMCID: PMC4057727 DOI: 10.3390/ijms15058186] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 04/18/2014] [Accepted: 04/24/2014] [Indexed: 12/25/2022] Open
Abstract
In durum wheat mitochondria (DWM) the ATP-inhibited plant mitochondrial potassium channel (PmitoK(ATP)) and the plant uncoupling protein (PUCP) are able to strongly reduce the proton motive force (pmf) to control mitochondrial production of reactive oxygen species; under these conditions, mitochondrial carriers lack the driving force for transport and should be inactive. However, unexpectedly, DWM uncoupling by PmitoK(ATP) neither impairs the exchange of ADP for ATP nor blocks the inward transport of Pi and succinate. This uptake may occur via the plant inner membrane anion channel (PIMAC), which is physiologically inhibited by membrane potential, but unlocks its activity in de-energized mitochondria. Probably, cooperation between PIMAC and carriers may accomplish metabolite movement across the inner membrane under both energized and de-energized conditions. PIMAC may also cooperate with PmitoK(ATP) to transport ammonium salts in DWM. Interestingly, this finding may trouble classical interpretation of in vitro mitochondrial swelling; instead of free passage of ammonia through the inner membrane and proton symport with Pi, that trigger metabolite movements via carriers, transport of ammonium via PmitoK(ATP) and that of the counteranion via PIMAC may occur. Here, we review properties, modulation and function of the above reported DWM channels and carriers to shed new light on the control that they exert on pmf and vice-versa.
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Affiliation(s)
- Daniela Trono
- Consiglio per la Ricerca e la sperimentazione in Agricoltura, Centro di Ricerca per la Cerealicoltura, S.S. 673 Km 25, 71122 Foggia, Italy.
| | - Maura N Laus
- Dipartimento di Scienze Agrarie, degli Alimenti e dell'Ambiente, Università di Foggia, Via Napoli 25, 71122 Foggia, Italy.
| | - Mario Soccio
- Dipartimento di Scienze Agrarie, degli Alimenti e dell'Ambiente, Università di Foggia, Via Napoli 25, 71122 Foggia, Italy.
| | - Donato Pastore
- Dipartimento di Scienze Agrarie, degli Alimenti e dell'Ambiente, Università di Foggia, Via Napoli 25, 71122 Foggia, Italy.
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Pastore D, Soccio M, Laus MN, Trono D. The uniqueness of the plant mitochondrial potassium channel. BMB Rep 2013; 46:391-7. [PMID: 23977986 PMCID: PMC4133908 DOI: 10.5483/bmbrep.2013.46.8.075] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Revised: 04/11/2013] [Accepted: 04/11/2013] [Indexed: 01/27/2023] Open
Abstract
The ATP-inhibited Plant Mitochondrial K(+) Channel (PmitoKATP) was discovered about fifteen years ago in Durum Wheat Mitochondria (DWM). PmitoKATP catalyses the electrophoretic K(+) uniport through the inner mitochondrial membrane; moreover, the co-operation between PmitoKATP and K(+)/H(+) antiporter allows such a great operation of a K(+) cycle to collapse mitochondrial membrane potential (ΔΨ) and ΔpH, thus impairing protonmotive force (Δp). A possible physiological role of such ΔΨ control is the restriction of harmful reactive oxygen species (ROS) production under environmental/oxidative stress conditions. Interestingly, DWM lacking Δp were found to be nevertheless fully coupled and able to regularly accomplish ATP synthesis; this unexpected behaviour makes necessary to recast in some way the classical chemiosmotic model. In the whole, PmitoKATP may oppose to large scale ROS production by lowering ΔΨ under environmental/oxidative stress, but, when stress is moderate, this occurs without impairing ATP synthesis in a crucial moment for cell and mitochondrial bioenergetics.
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Affiliation(s)
- Donato Pastore
- Dipartimento di Scienze Agrarie, degli Alimenti e dell'Ambiente, Università di Foggia, Via Napoli 25-71122 Foggia, Italy.
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A new simple fluorimetric method to assay cytosolic ATP content: application to durum wheat seedlings to assess modulation of mitochondrial potassium channel and uncoupling protein activity under hyperosmotic stress. Biologia (Bratisl) 2013. [DOI: 10.2478/s11756-013-0176-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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The mitochondrial permeability transition pore (PTP) — An example of multiple molecular exaptation? BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:2072-86. [DOI: 10.1016/j.bbabio.2012.06.620] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Revised: 06/19/2012] [Accepted: 06/21/2012] [Indexed: 11/21/2022]
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Trono D, Soccio M, Laus MN, Pastore D. Potassium channel-oxidative phosphorylation relationship in durum wheat mitochondria from control and hyperosmotic-stressed seedlings. PLANT, CELL & ENVIRONMENT 2011; 34:2093-108. [PMID: 21819416 DOI: 10.1111/j.1365-3040.2011.02407.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Durum wheat mitochondria (DWM) possess an ATP-inhibited K(+) channel, the plant mitoK(ATP) (PmitoK(ATP) ), which is activated under environmental stress to control mitochondrial ROS production. To do this, PmitoK(ATP) collapses membrane potential (ΔΨ), thus suggesting mitochondrial uncoupling. We tested this point by studying oxidative phosphorylation (OXPHOS) in DWM purified from control seedlings and from seedlings subjected both to severe mannitol and NaCl stress. In severely-stressed DWM, the ATP synthesis via OXPHOS, continuously monitored by a spectrophotometric assay, was about 90% inhibited when the PmitoK(ATP) was activated by KCl. Contrarily, in control DWM, although PmitoK(ATP) collapsed ΔΨ, ATP synthesis, as well as coupling [respiratory control (RC) ratio and ratio between phosphorylated ADP and reduced oxygen (ADP/O)] checked by oxygen uptake experiments, were unaffected. We suggest that PmitoK(ATP) may play an important defensive role at the onset of the environmental/oxidative stress by preserving energy in a crucial moment for cell and mitochondrial bioenergetics. Consistently, under moderate mannitol stress, miming an early stress condition, the channel may efficiently control reactive oxygen species (ROS) generation (about 35-fold from fully open to closed state) without impairing ATP synthesis. Anyway, if the stress significantly proceeds, the PmitoK(ATP) becomes fully activated by decrease of ATP concentration (25-40%) and increase of activators [free fatty acids (FFAs) and superoxide anion], thus impairing ATP synthesis.
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Affiliation(s)
- Daniela Trono
- CRA - Centro di Ricerca per la Cerealicoltura, S.S. 16 Km 675, Dipartimento di Scienze Agroambientali, Chimica e Difesa Vegetale, Università di Foggia, Via Napoli 25, Italy
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11
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Laus MN, Soccio M, Trono D, Liberatore MT, Pastore D. Activation of the plant mitochondrial potassium channel by free fatty acids and acyl-CoA esters: a possible defence mechanism in the response to hyperosmotic stress. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:141-54. [PMID: 20801915 DOI: 10.1093/jxb/erq256] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The effect of free fatty acids (FFAs) and acyl-CoA esters on K(+) uptake was studied in mitochondria isolated from durum wheat (Triticum durum Desf.), a species that has adapted well to the semi-arid Mediterranean area and possessing a highly active mitochondrial ATP-sensitive K(+) channel (PmitoK(ATP)), that may confer resistance to environmental stresses. This was made by swelling experiments in KCl solution under experimental conditions in which PmitoK(ATP) activity was monitored. Linoleate and other FFAs (laurate, palmitate, stearate, palmitoleate, oleate, arachidonate, and the non-physiological 1-undecanesulphonate and 5-phenylvalerate), used at a concentration (10 μM) unable to damage membranes of isolated mitochondria, stimulated K(+) uptake by about 2-4-fold. Acyl-CoAs also promoted K(+) transport to a much larger extent with respect to FFAs (about 5-12-fold). In a different experimental system based on safranin O fluorescence measurements, the dissipation of electrical membrane potential induced by K(+) uptake via PmitoK(ATP) was found to increase in the presence of 5-phenylvalerate and palmitoyl-CoA, both unable to elicit the activity of the Plant Uncoupling Protein. This result suggests a direct activation of PmitoK(ATP). Stimulation of K(+) transport by FFAs/acyl-CoAs resulted in a widespread phenomenon in plant mitochondria from different mono/dicotyledonous species (bread wheat, barley, triticale, maize, lentil, pea, and topinambur) and from different organs (root, tuber, leaf, and shoot). Finally, an increase in mitochondrial FFAs up to a content of 50 nmol mg(-1) protein, which was able to activate PmitoK(ATP) strongly, was observed under hyperosmotic stress conditions. Since PmitoK(ATP) may act against environmental/oxidative stress, its activation by FFAs/acyl-CoAs is proposed to represent a physiological defence mechanism.
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Affiliation(s)
- Maura N Laus
- Dipartimento di Scienze Agro-ambientali, Chimica e Difesa Vegetale, Facoltà di Agraria, Università degli Studi di Foggia, Via Napoli, 25-71122 Foggia, Italy
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12
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Sunderhaus S, Klodmann J, Lenz C, Braun HP. Supramolecular structure of the OXPHOS system in highly thermogenic tissue of Arum maculatum. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2010; 48:265-272. [PMID: 20144873 DOI: 10.1016/j.plaphy.2010.01.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2009] [Revised: 01/07/2010] [Accepted: 01/13/2010] [Indexed: 05/28/2023]
Abstract
The protein complexes of the mitochondrial respiratory chain associate in defined ways forming supramolecular structures called respiratory supercomplexes or respirasomes. In plants, additional oxidoreductases participate in respiratory electron transport, e.g. the so-called "alternative NAD(P)H dehydrogenases" or an extra terminal oxidase called "alternative oxidase" (AOX). These additional enzymes were previously reported not to form part of respiratory supercomplexes. However, formation of respiratory supercomplexes might indirectly affect "alternative respiration" because electrons can be channeled within the supercomplexes which reduces access of the alternative enzymes towards their electron donating substrates. Here we report an investigation on the supramolecular organization of the respiratory chain in thermogenic Arum maculatum appendix mitochondria, which are known to have a highly active AOX for heat production. Investigations based on mild membrane solubilization by digitonin and protein separation by blue native PAGE revealed a very special organization of the respiratory chain in A. maculatum, which strikingly differs to the one described for the model plant Arabidopsis thaliana: (i) complex I is not present in monomeric form but exclusively forms part of a I + III(2) supercomplex, (ii) the III(2) + IV and I + III(2) + IV supercomplexes are detectable but of low abundance, (iii) complex II has fewer subunits than in A. thaliana, and (iv) complex IV is mainly present as a monomer in a larger form termed "complex IVa". Since thermogenic tissue of A. maculatum at the same time has high AOX and I + III(2) supercomplex abundance and activity, negative regulation of the alternative oxidase by supercomplex formation seems not to occur. Functional implications are discussed.
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Affiliation(s)
- Stephanie Sunderhaus
- Institute for Plant Genetics, Faculty of Natural Sciences, Leibniz Universität Hannover, Herrenhäuser Str. 2, D-30419 Hannover, Germany
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13
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Blokhina O, Fagerstedt KV. Reactive oxygen species and nitric oxide in plant mitochondria: origin and redundant regulatory systems. PHYSIOLOGIA PLANTARUM 2010; 138:447-62. [PMID: 20059731 DOI: 10.1111/j.1399-3054.2009.01340.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Plant mitochondria differ from their mammalian counterparts in many respects, which are due to the unique and variable surroundings of plant mitochondria. In green leaves, plant mitochondria are surrounded by ample respiratory substrates and abundant molecular oxygen, both resulting from active photosynthesis, while in roots and bulky rhizomes and fruit carbohydrates may be plenty, whereas oxygen levels are falling. Several enzymatic complexes in mitochondrial electron transport chain (ETC) are capable of reactive oxygen species (ROS) formation under physiological and pathological conditions. Inherently connected parameters such as the redox state of electron carriers in the ETC, ATP synthase activity and inner mitochondrial membrane potential, when affected by external stimuli, can give rise to ROS formation via complexes I and III, and by reverse electron transport (RET) from complex II. Superoxide radicals produced are quickly scavenged by superoxide dismutase (MnSOD), and the resulting H(2)O(2) is detoxified by peroxiredoxin-thioredoxin system or by the enzymes of ascorbate-glutathione cycle, found in the mitochondrial matrix. Arginine-dependent nitric oxide (NO)-releasing activity of enzymatic origin has been detected in plant mitochondria. The molecular identity of the enzyme is not clear but the involvement of mitochondria-localized enzymes responsible for arginine catabolism, arginase and ornithine aminotransferase has been shown in the regulation of NO efflux. Besides direct control by antioxidants, mitochondrial ROS production is tightly controlled by multiple redundant systems affecting inner membrane potential: NAD(P)H-dependent dehydrogenases, alternative oxidase (AOX), uncoupling proteins, ATP-sensitive K(+) channel and a number of matrix and intermembrane enzymes capable of direct electron donation to ETC. NO removal, on the other hand, takes place either by reactions with molecular oxygen or superoxide resulting in peroxynitrite, nitrite or nitrate ions or through interaction with non-symbiotic hemoglobins or glutathione. Mitochondrial ROS and NO production is tightly controlled by multiple redundant systems providing the regulatory mechanism for redox homeostasis and specific ROS/NO signaling.
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Affiliation(s)
- Olga Blokhina
- Department of Biological and Environmental Sciences, University of Helsinki, P.O. Box 65, FI-00014 Helsinki, Finland.
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Petrussa E, Bertolini A, Casolo V, Krajnáková J, Macrì F, Vianello A. Mitochondrial bioenergetics linked to the manifestation of programmed cell death during somatic embryogenesis of Abies alba. PLANTA 2009; 231:93-107. [PMID: 19834734 DOI: 10.1007/s00425-009-1028-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2009] [Accepted: 09/17/2009] [Indexed: 05/05/2023]
Abstract
The present work reports changes in bioenergetic parameters and mitochondrial activities during the manifestation of two events of programmed cell death (PCD), linked to Abies alba somatic embryogenesis. PCD, evidenced by in situ nuclear DNA fragmentation (TUNEL assay), DNA laddering and cytochrome c release, was decreased in maturing embryogenic tissue with respect to the proliferation stage. In addition, the major cellular energetic metabolites (ATP, NAD(P)H and glucose-6-phosphate) were highered during maturation. The main mitochondrial activities changed during two developmental stages. Mitochondria, isolated from maturing, with respect to proliferating cell masses, showed an increased activity of the alternative oxidase, external NADH dehydrogenase and fatty-acid mediated uncoupling. Conversely, a significant decrease of the mitochondrial K (ATP)(+) channel activity was observed. These results suggest a correlation between mitochondrial activities and the manifestation of PCD during the development of somatic embryos. In particular, it is suggested that the K (ATP)(+) channel activity could induce an entry of K(+) into the matrix, followed by swelling and a release of cytochrome c during proliferation, whereas the alternative pathways, acting as anti-apoptotic factors, may partially counteract PCD events occurring during maturation of somatic embryos.
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Affiliation(s)
- Elisa Petrussa
- Section of Plant Biology, Department of Biology and Plant Protection, University of Udine, via delle Scienze 91, 33100, Udine, Italy
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