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Garmash EV. Role of mitochondrial alternative oxidase in the regulation of cellular homeostasis during development of photosynthetic function in greening leaves. PLANT BIOLOGY (STUTTGART, GERMANY) 2021; 23:221-228. [PMID: 33190385 DOI: 10.1111/plb.13217] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 11/08/2020] [Indexed: 05/27/2023]
Abstract
Here, recent publications on the role of mitochondrial non-phosphorylating pathways (NPhPs) in the electron transport chain during the de-etiolation of wheat leaves are reviewed. Among NPhPs, the alternative oxidase (AOX) pathway is the most effective pathway in maintaining cellular redox and energy balance, especially under stress conditions, including light stress. AOX is considered to dissipate excess reductants produced in the chloroplasts, and thereby prevent photooxidation. However, when etiolated wheat plants were exposed to a physiologically relevant light level, AOX was rapidly induced and increased, although the etioplasts did not produce excess reductants and have their own strong photoprotective mechanisms. The present study provides further insights into the role of AOX in greening cells and highlights the importance of AOX in the integration of cellular signalling pathways.
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Affiliation(s)
- E V Garmash
- Institute of Biology, Komi Scientific Centre, Ural Branch, Russian Academy of Sciences, Syktyvkar, 167982, Russian Federation
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2
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Igamberdiev AU. Citrate valve integrates mitochondria into photosynthetic metabolism. Mitochondrion 2020; 52:218-230. [PMID: 32278088 DOI: 10.1016/j.mito.2020.04.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Revised: 03/21/2020] [Accepted: 04/07/2020] [Indexed: 12/31/2022]
Abstract
While in heterotrophic cells and in darkness mitochondria serve as main producers of energy, during photosynthesis this function is transferred to chloroplasts and the main role of mitochondria in bioenergetics turns to be the balance of the level of phosphorylation of adenylates and of reduction of pyridine nucleotides to avoid over-energization of the cell and optimize major metabolic fluxes. This is achieved via the establishment and regulation of local equilibria of the tricarboxylic acid (TCA) cycle enzymes malate dehydrogenase and fumarase in one branch and aconitase and isocitrate dehydrogenase in another branch. In the conditions of elevation of redox level, the TCA cycle is transformed into a non-cyclic open structure (hemicycle) leading to the export of the tricarboxylic acid (citrate) to the cytosol and to the accumulation of the dicarboxylic acids (malate and fumarate). While the buildup of NADPH in chloroplasts provides operation of the malate valve leading to establishment of NADH/NAD+ ratios in different cell compartments, the production of NADH by mitochondria drives citrate export by establishing conditions for the operation of the citrate valve. The latter regulates the intercompartmental NADPH/NADP+ ratio and contributes to the biosynthesis of amino acids and other metabolic products during photosynthesis.
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Affiliation(s)
- Abir U Igamberdiev
- Department of Biology, Memorial University of Newfoundland, St. John's, NL A1B 3X9, Canada.
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3
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Florez-Sarasa I, Obata T, Del-Saz NSFN, Reichheld JP, Meyer EH, Rodriguez-Concepcion M, Ribas-Carbo M, Fernie AR. The Lack of Mitochondrial Thioredoxin TRXo1 Affects In Vivo Alternative Oxidase Activity and Carbon Metabolism under Different Light Conditions. PLANT & CELL PHYSIOLOGY 2019; 60:2369-2381. [PMID: 31318380 DOI: 10.1093/pcp/pcz123] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 06/17/2019] [Indexed: 05/04/2023]
Abstract
The alternative oxidase (AOX) constitutes a nonphosphorylating pathway of electron transport in the mitochondrial respiratory chain that provides flexibility to energy and carbon primary metabolism. Its activity is regulated in vitro by the mitochondrial thioredoxin (TRX) system which reduces conserved cysteines residues of AOX. However, in vivo evidence for redox regulation of the AOX activity is still scarce. In the present study, the redox state, protein levels and in vivo activity of the AOX in parallel to photosynthetic parameters were determined in Arabidopsis knockout mutants lacking mitochondrial trxo1 under moderate (ML) and high light (HL) conditions, known to induce in vivo AOX activity. In addition, 13C- and 14C-labeling experiments together with metabolite profiling were performed to better understand the metabolic coordination between energy and carbon metabolism in the trxo1 mutants. Our results show that the in vivo AOX activity is higher in the trxo1 mutants at ML while the AOX redox state is apparently unaltered. These results suggest that mitochondrial thiol redox systems are responsible for maintaining AOX in its reduced form rather than regulating its activity in vivo. Moreover, the negative regulation of the tricarboxylic acid cycle by the TRX system is coordinated with the increased input of electrons into the AOX pathway. Under HL conditions, while AOX and photosynthesis displayed similar patterns in the mutants, photorespiration is restricted at the level of glycine decarboxylation most likely as a consequence of redox imbalance.
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Affiliation(s)
- Igor Florez-Sarasa
- Max-Planck-Institut f�r Molekulare Pflanzenphysiologie, Am M�hlenberg 1, Potsdam-Golm, Germany
- Centre for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB-UB, Campus UAB Bellaterra, Barcelona, Spain
| | - Toshihiro Obata
- Max-Planck-Institut f�r Molekulare Pflanzenphysiologie, Am M�hlenberg 1, Potsdam-Golm, Germany
- University of Nebraska Lincoln, 1901 Vine Street, Lincoln, NE, USA
| | - Nï Stor Fernï Ndez Del-Saz
- Grup de Recerca en Biologia de les Plantes en Condicions Mediterranies, Departament de Biologia, Universitat de les Illes Balears, Carretera de Valldemossa Km 7.5, Palma de Mallorca, Spain
- Departamento de Bot�nica, Facultad de Ciencias Naturales y Oceanogr�ficas, Universidad de Concepci�n, Concepci�n, Chile
| | | | - Etienne H Meyer
- Max-Planck-Institut f�r Molekulare Pflanzenphysiologie, Am M�hlenberg 1, Potsdam-Golm, Germany
| | - Manuel Rodriguez-Concepcion
- Centre for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB-UB, Campus UAB Bellaterra, Barcelona, Spain
| | - Miquel Ribas-Carbo
- Grup de Recerca en Biologia de les Plantes en Condicions Mediterranies, Departament de Biologia, Universitat de les Illes Balears, Carretera de Valldemossa Km 7.5, Palma de Mallorca, Spain
| | - Alisdair R Fernie
- Max-Planck-Institut f�r Molekulare Pflanzenphysiologie, Am M�hlenberg 1, Potsdam-Golm, Germany
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4
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Umekawa Y, Ito K. Thioredoxin o-mediated reduction of mitochondrial alternative oxidase in the thermogenic skunk cabbage Symplocarpus renifolius. J Biochem 2019; 165:57-65. [PMID: 30289493 PMCID: PMC6299270 DOI: 10.1093/jb/mvy082] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Accepted: 10/04/2018] [Indexed: 11/21/2022] Open
Abstract
Thermogenesis in plants involves significant increases in their cyanide-resistant mitochondrial alternative oxidase (AOX) capacity. Because AOX is a non-proton-motive ubiquinol oxidase, the dramatic drop in free energy between ubiquinol and oxygen is dissipated as heat. In the thermogenic skunk cabbage (Symplocarpus renifolius), SrAOX is specifically expressed in the florets. Although SrAOX harbours conserved cysteine residues, the details of the mechanisms underlying its redox regulation are poorly understood. In our present study, the two mitochondrial thioredoxin o cDNAs SrTrxo1 and SrTrxo2, were isolated from the thermogenic florets of S. renifolius. The deduced amino acid sequences of the protein products revealed that SrTrxo2 specifically lacks the region corresponding to the α3-helix in SrTrxo1. Expression analysis of thermogenic and non-thermogenic S. renifolius tissues indicated that the SrTrxo1 and SrAOX transcripts are predominantly expressed together in thermogenic florets, whereas SrTrxo2 transcripts are almost undetectable in any tissue. Finally, functional in vitro analysis of recombinant SrTrxo1 and mitochondrial membrane fractions of thermogenic florets indicated its reducing activity on SrAOX proteins. Taken together, these results indicate that SrTrxo1 is likely to play a role in the redox regulation of SrAOX in S. renifolius thermogenic florets.
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Affiliation(s)
- Yui Umekawa
- Cryobiofrontier Research Center, Faculty of Agriculture, Iwate University, 3-18-8 Ueda, Morioka, Iwate, Japan
| | - Kikukatsu Ito
- Cryobiofrontier Research Center, Faculty of Agriculture, Iwate University, 3-18-8 Ueda, Morioka, Iwate, Japan.,Department of Biological Chemistry and Food Science, Faculty of Agriculture, Iwate University, 3-18-8 Ueda, Morioka, Iwate, Japan.,Agri-Innovation Research Center, Iwate University, 3-18-8 Ueda, Morioka, Iwate, Japan
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5
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Leterrier M, Barroso JB, Valderrama R, Begara-Morales JC, Sánchez-Calvo B, Chaki M, Luque F, Viñegla B, Palma JM, Corpas FJ. Peroxisomal NADP-isocitrate dehydrogenase is required for Arabidopsis stomatal movement. PROTOPLASMA 2016; 253:403-15. [PMID: 25894616 DOI: 10.1007/s00709-015-0819-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 04/08/2015] [Indexed: 05/21/2023]
Abstract
Peroxisomes are subcellular organelles characterized by a simple morphological structure but have a complex biochemical machinery involved in signaling processes through molecules such as hydrogen peroxide (H2O2) and nitric oxide (NO). Nicotinamide adenine dinucleotide phosphate (NADPH) is an essential component in cell redox homeostasis, and its regeneration is critical for reductive biosynthesis and detoxification pathways. Plants have several NADPH-generating dehydrogenases, with NADP-isocitrate dehydrogenase (NADP-ICDH) being one of these enzymes. Arabidopsis contains three genes that encode for cytosolic, mitochondrial/chloroplastic, and peroxisomal NADP-ICDH isozymes although the specific function of each of these remains largely unknown. Using two T-DNA insertion lines of the peroxisomal NADP-ICDH designated as picdh-1 and picdh-2, the data show that the peroxisomal NADP-ICDH is involved in stomatal movements, suggesting that peroxisomes are a new element in the signaling network of guard cells.
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Affiliation(s)
- Marina Leterrier
- Group of Antioxidants, Free Radicals and Nitric Oxide in Biotechnology, Food and Agriculture, Department of Biochemistry, Cell and Molecular Biology of Plants, Estación Experimental del Zaidín, CSIC, Apartado 419, 18080, Granada, Spain
| | - Juan B Barroso
- Group of Biochemistry and Cell Signaling in Nitric Oxide, Department of Biochemistry and Molecular Biology, University of Jaén, Campus "Las Lagunillas", 23071, Jaén, Spain
| | - Raquel Valderrama
- Group of Biochemistry and Cell Signaling in Nitric Oxide, Department of Biochemistry and Molecular Biology, University of Jaén, Campus "Las Lagunillas", 23071, Jaén, Spain
| | - Juan C Begara-Morales
- Group of Biochemistry and Cell Signaling in Nitric Oxide, Department of Biochemistry and Molecular Biology, University of Jaén, Campus "Las Lagunillas", 23071, Jaén, Spain
| | - Beatriz Sánchez-Calvo
- Group of Biochemistry and Cell Signaling in Nitric Oxide, Department of Biochemistry and Molecular Biology, University of Jaén, Campus "Las Lagunillas", 23071, Jaén, Spain
| | - Mounira Chaki
- Group of Antioxidants, Free Radicals and Nitric Oxide in Biotechnology, Food and Agriculture, Department of Biochemistry, Cell and Molecular Biology of Plants, Estación Experimental del Zaidín, CSIC, Apartado 419, 18080, Granada, Spain
| | - Francisco Luque
- Group of Biochemistry and Cell Signaling in Nitric Oxide, Department of Biochemistry and Molecular Biology, University of Jaén, Campus "Las Lagunillas", 23071, Jaén, Spain
| | - Benjamin Viñegla
- Departamento de Biología Animal, Biología Vegetal y Ecología (Ecología), Facultad de Ciencias Experimentales, Universidad de Jaén, Jaén, Spain
| | - José M Palma
- Group of Antioxidants, Free Radicals and Nitric Oxide in Biotechnology, Food and Agriculture, Department of Biochemistry, Cell and Molecular Biology of Plants, Estación Experimental del Zaidín, CSIC, Apartado 419, 18080, Granada, Spain
| | - Francisco J Corpas
- Group of Antioxidants, Free Radicals and Nitric Oxide in Biotechnology, Food and Agriculture, Department of Biochemistry, Cell and Molecular Biology of Plants, Estación Experimental del Zaidín, CSIC, Apartado 419, 18080, Granada, Spain.
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6
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Zhang DW, Yuan S, Xu F, Zhu F, Yuan M, Ye HX, Guo HQ, Lv X, Yin Y, Lin HH. Light intensity affects chlorophyll synthesis during greening process by metabolite signal from mitochondrial alternative oxidase in Arabidopsis. PLANT, CELL & ENVIRONMENT 2016; 39:12-25. [PMID: 25158995 DOI: 10.1111/pce.12438] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Revised: 08/01/2014] [Accepted: 08/03/2014] [Indexed: 05/08/2023]
Abstract
Although mitochondrial alternative oxidase (AOX) has been proposed to play essential roles in high light stress tolerance, the effects of AOX on chlorophyll synthesis are unclear. Previous studies indicated that during greening, chlorophyll accumulation was largely delayed in plants whose mitochondrial cyanide-resistant respiration was inhibited by knocking out nuclear encoded AOX gene. Here, we showed that this delay of chlorophyll accumulation was more significant under high light condition. Inhibition of cyanide-resistant respiration was also accompanied by the increase of plastid NADPH/NADP(+) ratio, especially under high light treatment which subsequently blocked the import of multiple plastidial proteins, such as some components of the photosynthetic electron transport chain, the Calvin-Benson cycle enzymes and malate/oxaloacetate shuttle components. Overexpression of AOX1a rescued the aox1a mutant phenotype, including the chlorophyll accumulation during greening and plastidial protein import. It thus suggests that light intensity affects chlorophyll synthesis during greening process by a metabolic signal, the AOX-derived plastidial NADPH/NADP(+) ratio change. Further, our results thus revealed a molecular mechanism of chloroplast-mitochondria interactions.
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Affiliation(s)
- Da-Wei Zhang
- Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610064, China
- Department of Genetics, Development, and Cell Biology, Plant Science Institute, Iowa State University, Ames, IA, 50011, USA
| | - Shu Yuan
- Institute of Ecological and Environmental Sciences, College of Resources and Environmental Sciences, Sichuan Agricultural University, Chengdu, 611130, China
| | - Fei Xu
- Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610064, China
| | - Feng Zhu
- Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610064, China
| | - Ming Yuan
- College of Biology and Science, Sichuan Agricultural University, Ya'an, 625014, China
| | - Hua-Xun Ye
- Department of Genetics, Development, and Cell Biology, Plant Science Institute, Iowa State University, Ames, IA, 50011, USA
| | - Hong-Qing Guo
- Department of Genetics, Development, and Cell Biology, Plant Science Institute, Iowa State University, Ames, IA, 50011, USA
| | - Xin Lv
- Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610064, China
| | - Yanhai Yin
- Department of Genetics, Development, and Cell Biology, Plant Science Institute, Iowa State University, Ames, IA, 50011, USA
| | - Hong-Hui Lin
- Ministry of Education Key Laboratory for Bio-Resource and Eco-Environment, College of Life Science, State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, 610064, China
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7
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Rogov AG, Sukhanova EI, Uralskaya LA, Aliverdieva DA, Zvyagilskaya RA. Alternative oxidase: distribution, induction, properties, structure, regulation, and functions. BIOCHEMISTRY (MOSCOW) 2015; 79:1615-34. [PMID: 25749168 DOI: 10.1134/s0006297914130112] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The respiratory chain in the majority of organisms with aerobic type metabolism features the concomitant existence of the phosphorylating cytochrome pathway and the cyanide- and antimycin A-insensitive oxidative route comprising a so-called alternative oxidase (AOX) as a terminal oxidase. In this review, the history of AOX discovery is described. Considerable evidence is presented that AOX occurs widely in organisms at various levels of organization and is not confined to the plant kingdom. This enzyme has not been found only in Archaea, mammals, some yeasts and protists. Bioinformatics research revealed the sequences characteristic of AOX in representatives of various taxonomic groups. Based on multiple alignments of these sequences, a phylogenetic tree was constructed to infer their possible evolution. The ways of AOX activation, as well as regulatory interactions between AOX and the main respiratory chain are described. Data are summarized concerning the properties of AOX and the AOX-encoding genes whose expression is either constitutive or induced by various factors. Information is presented on the structure of AOX, its active center, and the ubiquinone-binding site. The principal functions of AOX are analyzed, including the cases of cell survival, optimization of respiratory metabolism, protection against excess of reactive oxygen species, and adaptation to variable nutrition sources and to biotic and abiotic stress factors. It is emphasized that different AOX functions complement each other in many instances and are not mutually exclusive. Examples are given to demonstrate that AOX is an important tool to overcome the adverse aftereffects of restricted activity of the main respiratory chain in cells and whole animals. This is the first comprehensive review on alternative oxidases of various organisms ranging from yeasts and protists to vascular plants.
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Affiliation(s)
- A G Rogov
- Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow, 119071, Russia.
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8
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Moore AL, Shiba T, Young L, Harada S, Kita K, Ito K. Unraveling the heater: new insights into the structure of the alternative oxidase. ANNUAL REVIEW OF PLANT BIOLOGY 2013; 64:637-63. [PMID: 23638828 DOI: 10.1146/annurev-arplant-042811-105432] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The alternative oxidase is a membrane-bound ubiquinol oxidase found in the majority of plants as well as many fungi and protists, including pathogenic organisms such as Trypanosoma brucei. It catalyzes a cyanide- and antimycin-A-resistant oxidation of ubiquinol and the reduction of oxygen to water, short-circuiting the mitochondrial electron-transport chain prior to proton translocation by complexes III and IV, thereby dramatically reducing ATP formation. In plants, it plays a key role in cellular metabolism, thermogenesis, and energy homeostasis and is generally considered to be a major stress-induced protein. We describe recent advances in our understanding of this protein's structure following the recent successful crystallization of the alternative oxidase from T. brucei. We focus on the nature of the active site and ubiquinol-binding channels and propose a mechanism for the reduction of oxygen to water based on these structural insights. We also consider the regulation of activity at the posttranslational and retrograde levels and highlight challenges for future research.
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Affiliation(s)
- Anthony L Moore
- Biochemistry and Molecular Biology, School of Life Sciences, University of Sussex, Brighton BN1 9QG, United Kingdom.
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9
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Foyer CH, Noctor G, Hodges M. Respiration and nitrogen assimilation: targeting mitochondria-associated metabolism as a means to enhance nitrogen use efficiency. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:1467-82. [PMID: 21282329 DOI: 10.1093/jxb/erq453] [Citation(s) in RCA: 135] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Considerable advances in our understanding of the control of mitochondrial metabolism and its interactions with nitrogen metabolism and associated carbon/nitrogen interactions have occurred in recent years, particularly highlighting important roles in cellular redox homeostasis. The tricarboxylic acid (TCA) cycle is a central metabolic hub for the interacting pathways of respiration, nitrogen assimilation, and photorespiration, with components that show considerable flexibility in relation to adaptations to the different functions of mitochondria in photosynthetic and non-photosynthetic cells. By comparison, the operation of the oxidative pentose phosphate pathway appears to represent a significant limitation to nitrogen assimilation in non-photosynthetic tissues. Valuable new insights have been gained concerning the roles of the different enzymes involved in the production of 2-oxoglutarate (2-OG) for ammonia assimilation, yielding an improved understanding of the crucial role of cellular energy balance as a broker of co-ordinate regulation. Taken together with new information on the mechanisms that co-ordinate the expression of genes involved in organellar functions, including energy metabolism, and the potential for exploiting the existing flexibility for NAD(P)H utilization in the respiratory electron transport chain to drive nitrogen assimilation, the evidence that mitochondrial metabolism and machinery are potential novel targets for the enhancement of nitrogen use efficiency (NUE) is explored.
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Affiliation(s)
- Christine H Foyer
- Centre for Plant Sciences, Faculty of Biology, University of Leeds, Leeds LS2 9JT, UK
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Xu F, Yuan S, Lin HH. Response of mitochondrial alternative oxidase (AOX) to light signals. PLANT SIGNALING & BEHAVIOR 2011; 6:55-8. [PMID: 21270540 PMCID: PMC3122006 DOI: 10.4161/psb.6.1.14192] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2010] [Accepted: 11/12/2010] [Indexed: 05/03/2023]
Abstract
Mitochondrial alternative oxidase (AOX), the unique respiratory terminal oxidase in plants, catalyzes the energy wasteful cyanide (CN)-resistant respiration and plays a role in optimizing photosynthesis. Recent studies from our group indicated that AOX plays a crucial role in chloroplast protection under extreme environments, such as high light (HL). Genetic data suggest that AOX is upregulated by light that was mediated by photoreceptors (phytochromes, phototropins and cryptochromes), and it also might have a particular role in relieving the overreduction of chloroplasts. Physiological analyses further suggest that AOX is essential for the dark-to-light transition, especially in de-etiolation course. In this mini-review, we highlight recent progresses in understanding the beneficial interaction between photosynthesis and mitochondria metabolism and discuss the possible role and mechanism of AOX in dissipation of excess reduced equivalents for chloroplasts under high light condition.
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Affiliation(s)
- Fei Xu
- Ministry of Education Key Laboratory for Bio-Resource & Eco-Environment, College of Life Science, Sichuan University, Chengdu, China
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Zhang DW, Xu F, Zhang ZW, Chen YE, Du JB, Jia SD, Yuan S, Lin HH. Effects of light on cyanide-resistant respiration and alternative oxidase function in Arabidopsis seedlings. PLANT, CELL & ENVIRONMENT 2010; 33:2121-31. [PMID: 20716069 DOI: 10.1111/j.1365-3040.2010.02211.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Mitochondrial alternative oxidase (AOX), the unique respiratory terminal oxidase in plants, catalyzes the energy wasteful cyanide (CN)-resistant respiration and plays a role in optimizing photosynthesis. Although it has been demonstrated that leaf AOX is upregulated after illumination, the in vivo mechanism of AOX upregulation by light and its physiological significance are still unknown. In this report, red light and blue light-induced AOX (especially AOX1a) expressions were characterized. Phytochromes, phototropins and cryptochromes, all these photoreceptors mediate the light-response of AOX1a gene. When aox1a mutant seedlings were grown under a high-light (HL) condition, photobleaching was more evident in the mutant than the wild-type plants. More reactive oxygen species (ROS) accumulation and inefficient dissipation of chloroplast reducing-equivalents in aox1a mutant may account for its worse adaptation to HL stress. When etiolated seedlings were exposed to illumination for 4 h, chlorophyll accumulation was largely delayed in aox1a plants. We first suggest that more reduction of the photosynthetic electron transport chain and more accumulation of reducing-equivalents in the mutant during de-etiolation might be the main reasons.
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Affiliation(s)
- Da-Wei Zhang
- Ministry of Education Key Laboratory for Bio-Resource & Eco-Environment, College of Life Science, Sichuan University, Chengdu, China
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12
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Two-dimensional liquid chromatography technique coupled with mass spectrometry analysis to compare the proteomic response to cadmium stress in plants. J Biomed Biotechnol 2010; 2010:567510. [PMID: 20204056 PMCID: PMC2828102 DOI: 10.1155/2010/567510] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Revised: 10/09/2009] [Accepted: 12/19/2009] [Indexed: 12/03/2022] Open
Abstract
Plants are useful in studies of metal toxicity, because their physiological responses to different metals are correlated with the metal exposure dose and chemical state. Moreover a network of proteins and biochemical cascades that may lead to a controlled homeostasis of metals has been identified in many plant species. This paper focuses on the global protein variations that occur in a Populus nigra spp. clone (Poli) that has an exceptional tolerance to the presence of cadmium. Protein separation was based on a two-dimensional liquid chromatography technique. A subset of 20 out of 126 peaks were identified as being regulated differently under cadmium stress and were fingerprinted by MALDI-TOF. Proteins that were more abundant in the treated samples were located in the chloroplast and in the mitochondrion, suggesting the importance of these organelles in the response and adaptation to metal stress.
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Sienkiewicz-Porzucek A, Sulpice R, Osorio S, Krahnert I, Leisse A, Urbanczyk-Wochniak E, Hodges M, Fernie AR, Nunes-Nesi A. Mild reductions in mitochondrial NAD-dependent isocitrate dehydrogenase activity result in altered nitrate assimilation and pigmentation but do not impact growth. MOLECULAR PLANT 2010; 3:156-73. [PMID: 20035036 PMCID: PMC2807928 DOI: 10.1093/mp/ssp101] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2009] [Accepted: 10/30/2009] [Indexed: 05/17/2023]
Abstract
Transgenic tomato (Solanum lycopersicum) plants were generated expressing a fragment of the mitochondrial NAD-dependent isocitrate dehydrogenase gene (SlIDH1) in the antisense orientation. The transgenic plants displayed a mild reduction in the activity of the target enzyme in the leaves but essentially no visible alteration in growth from the wild-type. Fruit size and yield were, however, reduced. These plants were characterized by relatively few changes in photosynthetic parameters, but they displayed a minor decrease in maximum photosynthetic efficiency (Fv/Fm). Furthermore, a clear reduction in flux through the tricarboxylic acid (TCA) cycle was observed in the transformants. Additionally, biochemical analyses revealed that the transgenic lines exhibited considerably altered metabolism, being characterized by slight decreases in the levels of amino acids, intermediates of the TCA cycle, photosynthetic pigments, starch, and NAD(P)H levels, but increased levels of nitrate and protein. Results from these studies show that even small changes in mitochondrial NAD-dependent isocitrate dehydrogenase activity lead to noticeable alterations in nitrate assimilation and suggest the presence of different strategies by which metabolism is reprogrammed to compensate for this deficiency.
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Affiliation(s)
| | - Ronan Sulpice
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, 14476 Potsdam-Golm, Germany
| | - Sonia Osorio
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, 14476 Potsdam-Golm, Germany
| | - Ina Krahnert
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, 14476 Potsdam-Golm, Germany
| | - Andrea Leisse
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, 14476 Potsdam-Golm, Germany
| | | | - Michael Hodges
- Institute de Biotechnologie des Plantes, Unité Mixte de Recherche 8618, Centre National de la Recherche Scientifique, Université de Paris-Sud 11, 91405 Orsay Cedex, France
| | - Alisdair R. Fernie
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, 14476 Potsdam-Golm, Germany
- To whom correspondence should be addressed. E-mail , fax +49 (0)331 5678408, tel. +49 (0)331 5678211
| | - Adriano Nunes-Nesi
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, 14476 Potsdam-Golm, Germany
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14
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Igamberdiev AU, Kleczkowski LA. Metabolic systems maintain stable non-equilibrium via thermodynamic buffering. Bioessays 2009; 31:1091-9. [PMID: 19708023 DOI: 10.1002/bies.200900057] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Here, we analyze how the set of nucleotides in the cell is equilibrated and how this generates simple rules that help the cell to organize itself via maintenance of a stable non-equilibrium state. A major mechanism operating to achieve this state is thermodynamic buffering via high activities of equilibrating enzymes such as adenylate kinase. Under stable non-equilibrium, the ratios of free and Mg-bound adenylates, Mg(2+) and membrane potentials are interdependent and can be computed. The adenylate status is balanced with the levels of reduced and oxidized pyridine nucleotides through regulated uncoupling of the pyridine nucleotide pool from ATP production in mitochondria, and through oxidation of substrates non-coupled to NAD(+) reduction in peroxisomes. The set of adenylates and pyridine nucleotides constitutes a generalized cell energy status and determines rates of major metabolic fluxes. As the result, fluxes of energy and information become organized spatially and temporally, providing conditions for self-maintenance of metabolism.
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15
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Umbach AL, Lacey EP, Richter SJ. Temperature-sensitive alternative oxidase protein content and its relationship to floral reflectance in natural Plantago lanceolata populations. THE NEW PHYTOLOGIST 2008; 181:662-671. [PMID: 19021863 DOI: 10.1111/j.1469-8137.2008.02683.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
In many plant species, the alternative respiratory pathway consisting of alternative oxidase (AOX) is affected by growth temperature. The adaptive significance of this temperature-sensitivity is unresolved. Here, leaf and spike (flower cluster) AOX protein content and spike/floral reflectance of genotypes from European Plantago lanceolata populations found in regions differing in reproductive season temperatures were measured. Cloned genotypes grown at controlled warm and cool temperatures were used to assess the natural within- and between-population variation in AOX content, temperature-sensitive phenotypic plasticity in content, and the relationship between AOX and temperature-sensitive floral/spike reflectance. AOX content and plasticity were genetically variable. Leaf AOX content, although greater at cool temperature, was relatively low and not statistically different across populations. Spike AOX content was greater than in leaves. Spike AOX plasticity differed significantly among populations and climate-types and showed significant negative correlation with floral reflectance plasticity, which also varied among populations. Genotypes with more AOX at cool than at warm temperature had greater floral reflectance plasticity; genotypes with relatively more AOX at warm temperature had less floral reflectance plasticity. The data support the hypothesis that plasticity of AOX content in reproductive tissues is associated with long-term thermal acclimatization.
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Affiliation(s)
- Ann L Umbach
- DCMB Group/Biology Department, Box 90338, Duke University, Durham, NC, 27708, USA
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16
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McDonald AE. Alternative oxidase: an inter-kingdom perspective on the function and regulation of this broadly distributed 'cyanide-resistant' terminal oxidase. FUNCTIONAL PLANT BIOLOGY : FPB 2008; 35:535-552. [PMID: 32688810 DOI: 10.1071/fp08025] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2008] [Accepted: 07/11/2008] [Indexed: 06/11/2023]
Abstract
Alternative oxidase (AOX) is a terminal quinol oxidase located in the respiratory electron transport chain that catalyses the oxidation of quinol and the reduction of oxygen to water. However, unlike the cytochrome c oxidase respiratory pathway, the AOX pathway moves fewer protons across the inner mitochondrial membrane to generate a proton motive force that can be used to synthesise ATP. The energy passed to AOX is dissipated as heat. This appears to be very wasteful from an energetic perspective and it is likely that AOX fulfils some physiological function(s) that makes up for its apparent energetic shortcomings. An examination of the known taxonomic distribution of AOX and the specific organisms in which AOX has been studied has been used to explore themes pertaining to AOX function and regulation. A comparative approach was used to examine AOX function as it relates to the biochemical function of the enzyme as a quinol oxidase and associated topics, such as enzyme structure, catalysis and transcriptional expression and post-translational regulation. Hypotheses that have been put forward about the physiological function(s) of AOX were explored in light of some recent discoveries made with regard to species that contain AOX. Fruitful areas of research for the AOX community in the future have been highlighted.
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Affiliation(s)
- Allison E McDonald
- Department of Biology, The University of Western Ontario, Biological and Geological Sciences Building, London, Ontario N6A 5B7, Canada. Email
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17
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Centeno DC, Oliver SN, Nunes-Nesi A, Geigenberger P, Machado DN, Loureiro ME, Silva MAP, Fernie AR. Metabolic regulation of pathways of carbohydrate oxidation in potato (Solanum tuberosum) tubers. PHYSIOLOGIA PLANTARUM 2008; 133:744-54. [PMID: 18494735 DOI: 10.1111/j.1399-3054.2008.01109.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
In the present article we evaluate the consequence of tuber-specific expression of yeast invertase, on the pathways of carbohydrate oxidation, in potato (Solanum tuberosum L. cv. Desiree). We analysed the relative rates of glycolysis and the oxidative pentose phosphate pathway that these lines exhibited as well as the relative contributions of the cytochrome and alternative pathways of mitochondrial respiration. Enzymatic and protein abundance analysis revealed concerted upregulation of the glycolytic pathway and of specific enzymes of the tricarboxylic acid cycle and the alternative oxidase but invariant levels of enzymes of the oxidative pentose phosphate pathway and proteins of the cytochrome pathway. When taken together these experiments suggest that the overexpression of a cytosolic invertase (EC 3.2.1.26) results in a general upregulation of carbohydrate oxidation with increased flux through both the glycolytic and oxidative pentose phosphate pathways as well as the cytochrome and alternative pathways of oxidative phosphorylation. Moreover these data suggest that the upregulation of respiration is a consequence of enhanced efficient mitochondrial metabolism.
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Affiliation(s)
- Danilo C Centeno
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
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18
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Yoshida K, Terashima I, Noguchi K. Up-Regulation of Mitochondrial Alternative Oxidase Concomitant with Chloroplast Over-Reduction by Excess Light. ACTA ACUST UNITED AC 2007; 48:606-14. [PMID: 17339232 DOI: 10.1093/pcp/pcm033] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Alternative oxidase (AOX), the unique terminal oxidase in plant mitochondria, catalyzes the energy-wasteful cyanide (CN)-resistant respiration. Although it has been suggested that AOX might prevent chloroplast over-reduction through the efficient dissipation of excess reducing equivalents, direct evidence for this in the physiological context has been lacking. In this study, we examined the mitochondrial respiratory properties, especially AOX, connected to the accumulation of reducing equivalents in the chloroplasts and the activities of enzymes needed to transport the reducing equivalents. We used Arabidopsis thaliana mutants defective in cyclic electron flow around PSI, in which the reducing equivalents accumulate in the chloroplast stroma due to an unbalanced ATP/NADPH production ratio. These mutants showed higher activities of the enzymes needed to transport the reducing equivalents even in low-light growth conditions. The amounts of AOX protein and CN-resistant respiration in the mutants were also higher than those in the wild type. After high-light treatment, AOX, even in the wild type, was preferentially up-regulated concomitant with the accumulation of reducing equivalents in the chloroplasts and an increase in the activities of enzymes needed to transport reducing equivalents. These results indicate that AOX can dissipate the excess reducing equivalents, which are transported from the chloroplasts, and serve in efficient photosynthesis.
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Affiliation(s)
- Keisuke Yoshida
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043 Japan.
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19
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Campbell C, Atkinson L, Zaragoza-Castells J, Lundmark M, Atkin O, Hurry V. Acclimation of photosynthesis and respiration is asynchronous in response to changes in temperature regardless of plant functional group. THE NEW PHYTOLOGIST 2007; 176:375-389. [PMID: 17692077 DOI: 10.1111/j.1469-8137.2007.02183.x] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Gas exchange, fluorescence, western blot and chemical composition analyses were combined to assess if three functional groups (forbs, grasses and evergreen trees/shrubs) differed in acclimation of leaf respiration (R) and photosynthesis (A) to a range of growth temperatures (7, 14, 21 and 28 degrees C). When measured at a common temperature, acclimation was greater for R than for A and differed between leaves experiencing a 10-d change in growth temperature (PE) and leaves newly developed at each temperature (ND). As a result, the R : A ratio was temperature dependent, increasing in cold-acclimated plants. The balance was largely restored in ND leaves. Acclimation responses were similar among functional groups. Across the functional groups, cold acclimation was associated with increases in nonstructural carbohydrates and nitrogen. Cold acclimation of R was associated with an increase in abundance of alternative and/or cytochrome oxidases in a species-dependent manner. Cold acclimation of A was consistent with an initial decrease and subsequent recovery of thylakoid membrane proteins and increased abundance of proteins involved in the Calvin cycle. Overall, the results point to striking similarities in the extent and the biochemical underpinning of acclimation of R and A among contrasting functional groups differing in overall rates of metabolism, chemical composition and leaf structure.
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Affiliation(s)
- Catherine Campbell
- Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, S-901 87 Umeå, Sweden
- Department of Biology (Area 2), The University of York, PO Box 373, York YO10 5YW, UK
| | - Lindsey Atkinson
- Department of Biology (Area 2), The University of York, PO Box 373, York YO10 5YW, UK
| | | | - Maria Lundmark
- Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, S-901 87 Umeå, Sweden
| | - Owen Atkin
- Department of Biology (Area 2), The University of York, PO Box 373, York YO10 5YW, UK
| | - Vaughan Hurry
- Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, S-901 87 Umeå, Sweden
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20
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Noguchi K, Terashima I. Responses of spinach leaf mitochondria to low N availability. PLANT, CELL & ENVIRONMENT 2006; 29:710-9. [PMID: 17080620 DOI: 10.1111/j.1365-3040.2005.01457.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Low N availability induces carbohydrate accumulation in leaf cells, which often causes suppression of photosynthesis. Under low N supply, excess carbohydrates would be preferentially respired by the non-phosphorylating pathways, such as the alternative oxidase (AOX) and uncoupling protein (UCP), which would suppress the excessive increase in the ratio of C to N (C/N ratio). In leaves, however, responses of these pathways to the low N stress are still unknown. We examined the mitochondrial respiratory pathways in spinach leaves grown at three different N availabilities to clarify whether the respiratory pathways change depending on the N availabilities. With the decrease in N availability, leaf respiratory rates per leaf area decreased, but the rates on the leaf N basis were comparable. Using fumarase activities of whole leaf extracts and isolated mitochondria, we estimated mitochondrial protein contents per leaf N. The contents increased with the decrease in the N availability, that is, at the low N availability, N was preferentially invested into mitochondria. On the mitochondrial protein basis, capacities of cytochrome pathway (CP) and cytochrome c oxidase (COX) were comparable regardless of the N availabilities, whereas both AOX capacity and the amounts of AOX protein increased with the decrease in the N availability. Some enzymes of tricarboxylic acid (TCA) cycle, especially NAD-dependent malic enzyme (NAD-ME), showed higher capacities under lower N. On the other hand, amounts of UCP did not differ amongst the N availabilities. These results indicated that, under low N stress, AOX will be preferentially up-regulated and will efficiently consume excess carbohydrates, which leads to suppressing the rise in the C/N ratio to a moderate level.
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Affiliation(s)
- Ko Noguchi
- Department of Biology, Graduate School of Science, Osaka University, 1-1 Machikaneyama-Cho, Toyonaka, Osaka 560-0043, Japan.
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21
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Umbach AL, Ng VS, Siedow JN. Regulation of plant alternative oxidase activity: A tale of two cysteines. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1757:135-42. [PMID: 16457775 DOI: 10.1016/j.bbabio.2005.12.005] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2005] [Revised: 12/14/2005] [Accepted: 12/19/2005] [Indexed: 11/21/2022]
Abstract
Two Cys residues, Cys(I) and Cys(II), are present in most plant alternative oxidases (AOXs). Cys(I) inactivates AOX by forming a disulfide bond with the corresponding Cys(I) residue on the adjacent subunit of the AOX homodimer. When reduced, Cys(I) associates with alpha-keto acids, such as pyruvate, to activate AOX, an effect mimicked by charged amino acid substitutions at the Cys(I) site. Cys(II) may also be a site of AOX activity regulation, through interaction with the small alpha-keto acid, glyoxylate. Comparison of Arabidopsis AOX1a (AtAOX1a) mutants with single or double substitutions at Cys(I) and Cys(II) confirmed that glyoxylate interacted with either Cys, while the effect of pyruvate (or succinate for AtAOX1a substituted with Ala at Cys(I)) was limited to Cys(I). A variety of Cys(II) substitutions constitutively activated AtAOX1a, indicating that neither the catalytic site nor, unlike at Cys(I), charge repulsion is involved. Independent effects at each Cys were suggested by lack of Cys(II) substitution interference with pyruvate stimulation at Cys(I), and close to additive activation at the two sites. However, results obtained using diamide treatment to covalently link the AtAOX1a subunits by the disulfide bond indicated that Cys(I) must be in the reduced state for activation at Cys(II) to occur.
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Affiliation(s)
- Ann L Umbach
- DCMB Group/Biology Department, Box 91000, Duke University, Durham, NC 27708-1000, USA.
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22
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Umbach AL, Fiorani F, Siedow JN. Characterization of transformed Arabidopsis with altered alternative oxidase levels and analysis of effects on reactive oxygen species in tissue. PLANT PHYSIOLOGY 2005; 139:1806-20. [PMID: 16299171 PMCID: PMC1310561 DOI: 10.1104/pp.105.070763] [Citation(s) in RCA: 176] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The alternative oxidase (AOX) of plant mitochondria transfers electrons from the ubiquinone pool to oxygen without energy conservation. AOX can use reductant in excess of cytochrome pathway capacity, preventing reactive oxygen species (ROS) formation from an over-reduced ubiquinone pool, and thus may be involved in acclimation to oxidative stresses. The AOX connection with mitochondrial ROS has been investigated only in isolated mitochondria and suspension culture cells. To study ROS and AOX in whole plants, transformed lines of Arabidopsis (Arabidopsis thaliana) were generated: AtAOX1a overexpressors, AtAOX1a anti-sense plants, and overexpressors of a mutated, constitutively active AtAOX1a. In the presence of KCN, leaf tissue of either mutant or wild-type AOX overexpressors showed no increase in oxidative damage, whereas anti-sense lines had levels of damage greater than those observed for untransformed leaves. Similarly, ROS production increased markedly in anti-sense and untransformed, but not overexpressor, roots with KCN treatment. Thus, AOX functions in leaves and roots, as in suspension cells, to ameliorate ROS production when the cytochrome pathway is chemically inhibited. However, in contrast with suspension culture cells, no changes in leaf transcript levels of selected electron transport components or oxidative stress-related enzymes were detected under nonlimiting growth conditions, regardless of transformation type. Further, a microarray study using an anti-sense line showed AOX influences outside mitochondria, particularly in chloroplasts and on several carbon metabolism pathways. These results illustrate the value of expanding AOX transformant studies to whole tissues.
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Affiliation(s)
- Ann L Umbach
- Developmental, Cell, and Molecular Biology Group, Biology Department, Duke University, Durham, North Carolina 27708-1000, USA.
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23
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Scheibe R, Backhausen JE, Emmerlich V, Holtgrefe S. Strategies to maintain redox homeostasis during photosynthesis under changing conditions. JOURNAL OF EXPERIMENTAL BOTANY 2005; 56:1481-9. [PMID: 15851411 DOI: 10.1093/jxb/eri181] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Plants perform photosynthesis and assimilatory processes in a continuously changing environment. Energy production in the various cell compartments and energy consumption in endergonic processes have to be well adjusted to the varying conditions. In addition, dissipatory pathways are required to avoid any detrimental effects caused by over-reduction. A large number of short-term and long-term mechanisms interact with each other in a flexible way, depending on intensity and the type of impact. Therefore, all levels of regulation are involved, starting from energy absorption and electron flow events through to post-transcriptional control. The simultaneous presence of strong oxidants and strong reductants during oxygenic photosynthesis is the basis for regulation. However, redox-dependent control also interacts with other signal transduction pathways in order to adapt metabolic processes and redox-control to the developmental state. Examples are given here for short-term and long-term control following changes of light intensity and photoperiod, focusing on the dynamic nature of the plant regulatory systems. An integrating network of all these mechanisms exists at all levels of control. Cellular homeostasis will be maintained as long as the mechanisms for acclimation are present in sufficiently high capacities. If an impact is too rapid, and acclimation on the level of gene expression cannot occur, cellular damage and cell death are initiated.
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Affiliation(s)
- Renate Scheibe
- Department of Plant Physiology, Faculty of Biology and Chemistry, University of Osnabrueck, D-49069 Osnabrueck, Germany.
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