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Zhang Y, Liu Z, Xiao G, Shi J, Liu B, Xiao N, Sun Z. Simultaneous DHA and organic selenium production by Schizochytrium sp.: a theoretical basis. Sci Rep 2023; 13:15607. [PMID: 37731016 PMCID: PMC10511486 DOI: 10.1038/s41598-023-42900-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Accepted: 09/15/2023] [Indexed: 09/22/2023] Open
Abstract
Docosahexaenoic acid (DHA) and selenium (Se) are nutrients that confer several health benefits to both humans and animals. Widespread use of DHA in milk powder and health products requires large-scale mass production via Schizochytrium sp., while Se intended for human consumption is produced as organic Se via yeast. However, producing these nutrients on an industrial scale is constrained by various factors. We found that supplementing Schizochytrium sp. with Na2SeO3 (0.5 mg/L) improves its biomass and DHA production and also provides organic Se. De novo assembled transcriptome and biochemical indicators showed that Na2SeO3 promotes forming acetyl coenzyme A and L-cysteine via the glycerol kinase and cysteine synthase pathways, promoting DHA synthesis through the polyketide synthase pathway. However, high doses of Na2SeO3 (5 mg/L) limited the biomass of Schizochytrium sp. and DHA content. This study provided a theoretical basis for the simultaneous production of organic Se and DHA via Schizochytrium sp.
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Affiliation(s)
- Yunqiang Zhang
- Hunan Agricultural University Veterinary Faculty, No.1 Nongda Road, Furong District, Changsha City, 410000, Hunan, China
- Hunan Canzoho Biological Technology Co., Ltd., 321 Kangning Road, Changsha City, 410000, Hunan, China
| | - Zikui Liu
- Hunan Agricultural University Veterinary Faculty, No.1 Nongda Road, Furong District, Changsha City, 410000, Hunan, China
- Hunan Canzoho Biological Technology Co., Ltd., 321 Kangning Road, Changsha City, 410000, Hunan, China
| | - Gang Xiao
- Hunan Agricultural University Veterinary Faculty, No.1 Nongda Road, Furong District, Changsha City, 410000, Hunan, China
| | - Jiawei Shi
- Hunan Agricultural University Veterinary Faculty, No.1 Nongda Road, Furong District, Changsha City, 410000, Hunan, China
- Hunan Canzoho Biological Technology Co., Ltd., 321 Kangning Road, Changsha City, 410000, Hunan, China
| | - Baili Liu
- Hunan Canzoho Biological Technology Co., Ltd., 321 Kangning Road, Changsha City, 410000, Hunan, China
| | - Ning Xiao
- Hunan Agricultural University Veterinary Faculty, No.1 Nongda Road, Furong District, Changsha City, 410000, Hunan, China
| | - Zhiliang Sun
- Hunan Agricultural University Veterinary Faculty, No.1 Nongda Road, Furong District, Changsha City, 410000, Hunan, China.
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da Fonseca-Pereira P, Souza PVL, Fernie AR, Timm S, Daloso DM, Araújo WL. Thioredoxin-mediated regulation of (photo)respiration and central metabolism. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:5987-6002. [PMID: 33649770 DOI: 10.1093/jxb/erab098] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 02/24/2021] [Indexed: 06/12/2023]
Abstract
Thioredoxins (TRXs) are ubiquitous proteins engaged in the redox regulation of plant metabolism. Whilst the light-dependent TRX-mediated activation of Calvin-Benson cycle enzymes is well documented, the role of extraplastidial TRXs in the control of the mitochondrial (photo)respiratory metabolism has been revealed relatively recently. Mitochondrially located TRX o1 has been identified as a regulator of alternative oxidase, enzymes of, or associated with, the tricarboxylic acid (TCA) cycle, and the mitochondrial dihydrolipoamide dehydrogenase (mtLPD) involved in photorespiration, the TCA cycle, and the degradation of branched chain amino acids. TRXs are seemingly a major point of metabolic regulation responsible for activating photosynthesis and adjusting mitochondrial photorespiratory metabolism according to the prevailing cellular redox status. Furthermore, TRX-mediated (de)activation of TCA cycle enzymes contributes to explain the non-cyclic flux mode of operation of this cycle in illuminated leaves. Here we provide an overview on the decisive role of TRXs in the coordination of mitochondrial metabolism in the light and provide in silico evidence for other redox-regulated photorespiratory enzymes. We further discuss the consequences of mtLPD regulation beyond photorespiration and provide outstanding questions that should be addressed in future studies to improve our understanding of the role of TRXs in the regulation of central metabolism.
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Affiliation(s)
| | - Paulo V L Souza
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, Fortaleza, Ceará, Brazil
| | - Alisdair R Fernie
- Max-Planck-Institute of Molecular Plant Physiology, Potsdam-Golm, Germany
| | - Stefan Timm
- University of Rostock, Plant Physiology Department, Albert- Einstein-Str. 3, Rostock, Germany
| | - Danilo M Daloso
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, Fortaleza, Ceará, Brazil
| | - Wagner L Araújo
- Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil
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3
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Optimization of nucleotide sugar supply for polysaccharide formation via thermodynamic buffering. Biochem J 2020; 477:341-356. [PMID: 31967651 DOI: 10.1042/bcj20190807] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 12/16/2019] [Accepted: 12/18/2019] [Indexed: 02/07/2023]
Abstract
Plant polysaccharides (cellulose, hemicellulose, pectin, starch) are either direct (i.e. leaf starch) or indirect products of photosynthesis, and they belong to the most abundant organic compounds in nature. Although each of these polymers is made by a specific enzymatic machinery, frequently in different cell locations, details of their synthesis share certain common features. Thus, the production of these polysaccharides is preceded by the formation of nucleotide sugars catalyzed by fully reversible reactions of various enzymes, mostly pyrophosphorylases. These 'buffering' enzymes are, generally, quite active and operate close to equilibrium. The nucleotide sugars are then used as substrates for irreversible reactions of various polysaccharide-synthesizing glycosyltransferases ('engine' enzymes), e.g. plastidial starch synthases, or plasma membrane-bound cellulose synthase and callose synthase, or ER/Golgi-located variety of glycosyltransferases forming hemicellulose and pectin backbones. Alternatively, the irreversible step might also be provided by a carrier transporting a given immediate precursor across a membrane. Here, we argue that local equilibria, established within metabolic pathways and cycles resulting in polysaccharide production, bring stability to the system via the arrangement of a flexible supply of nucleotide sugars. This metabolic system is itself under control of adenylate kinase and nucleoside-diphosphate kinase, which determine the availability of nucleotides (adenylates, uridylates, guanylates and cytidylates) and Mg2+, the latter serving as a feedback signal from the nucleotide metabolome. Under these conditions, the supply of nucleotide sugars to engine enzymes is stable and constant, and the metabolic process becomes optimized in its load and consumption, making the system steady and self-regulated.
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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: 13] [Impact Index Per Article: 3.3] [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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Selinski J, Scheibe R. Malate valves: old shuttles with new perspectives. PLANT BIOLOGY (STUTTGART, GERMANY) 2019; 21 Suppl 1:21-30. [PMID: 29933514 PMCID: PMC6586076 DOI: 10.1111/plb.12869] [Citation(s) in RCA: 117] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 06/18/2018] [Indexed: 05/18/2023]
Abstract
Malate valves act as powerful systems for balancing the ATP/NAD(P)H ratio required in various subcellular compartments in plant cells. As components of malate valves, isoforms of malate dehydrogenases (MDHs) and dicarboxylate translocators catalyse the reversible interconversion of malate and oxaloacetate and their transport. Depending on the co-enzyme specificity of the MDH isoforms, either NADH or NADPH can be transported indirectly. Arabidopsis thaliana possesses nine genes encoding MDH isoenzymes. Activities of NAD-dependent MDHs have been detected in mitochondria, peroxisomes, cytosol and plastids. In addition, chloroplasts possess a NADP-dependent MDH isoform. The NADP-MDH as part of the 'light malate valve' plays an important role as a poising mechanism to adjust the ATP/NADPH ratio in the stroma. Its activity is strictly regulated by post-translational redox-modification mediated via the ferredoxin-thioredoxin system and fine control via the NADP+ /NADP(H) ratio, thereby maintaining redox homeostasis under changing conditions. In contrast, the plastid NAD-MDH ('dark malate valve') is constitutively active and its lack leads to failure in early embryo development. While redox regulation of the main cytosolic MDH isoform has been shown, knowledge about regulation of the other two cytosolic MDHs as well as NAD-MDH isoforms from peroxisomes and mitochondria is still lacking. Knockout mutants lacking the isoforms from chloroplasts, mitochondria and peroxisomes have been characterised, but not much is known about cytosolic NAD-MDH isoforms and their role in planta. This review updates the current knowledge on MDH isoforms and the shuttle systems for intercompartmental dicarboxylate exchange, focusing on the various metabolic functions of these valves.
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Affiliation(s)
- J. Selinski
- Department of Animal, Plant, and Soil ScienceAustralian Research Council Centre of Excellence in Plant Energy BiologySchool of Life ScienceLa Trobe University BundooraBundooraAustralia
| | - R. Scheibe
- Division of Plant PhysiologyDepartment of Biology/ChemistryUniversity of OsnabrueckOsnabrueckGermany
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Thermodynamic buffering, stable non-equilibrium and establishment of the computable structure of plant metabolism. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2018; 146:23-36. [PMID: 30444975 DOI: 10.1016/j.pbiomolbio.2018.11.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Revised: 11/02/2018] [Accepted: 11/12/2018] [Indexed: 01/09/2023]
Abstract
The equilibria of coenzyme nucleotides and substrates established in plant cells generate simple rules that govern the plant metabolome and provide optimal conditions for the non-equilibrium fluxes of major metabolic processes such as ATP synthesis, CO2 fixation, and mitochondrial respiration. Fast and abundant enzymes, such as adenylate kinase, carbonic anhydrase or malate dehydrogenase, provide constant substrate flux for these processes. These "buffering" enzymes follow the Michaelis-Menten (MM) kinetics and operate near equilibrium. The non-equilibrium "engine" enzymes, such as ATP synthase, Rubisco or the respiratory complexes, follow the modified version of MM kinetics due to their high concentration and low concentration of their substrates. The equilibrium reactions serve as control gates for the non-equilibrium flux through the engine enzymes establishing the balance of the fluxes of load and consumption of metabolic components. Under the coordinated operation of buffering and engine enzymes, the concentrations of free and Mg-bound adenylates and of free Mg2+ are set, serving as feedback signals from the adenylate metabolome. Those are linked to various cell energetics parameters, including membrane potentials. Also, internal levels of reduced and oxidized pyridine nucleotides are established in the coordinated operation of malate dehydrogenase and respiratory components, with proton concentration as a feedback from pyridine nucleotide pools. Non-coupled pathways of respiration serve to equilibrate the levels of pyridine nucleotides, adenylates, and as a pH stat. This stable non-equilibrium organizes the fluxes of energy spatially and temporally, controlling the rates of major metabolic fluxes that follow thermodynamically and kinetically defined computational principles.
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Igamberdiev AU, Bykova NV. Role of organic acids in the integration of cellular redox metabolism and mediation of redox signalling in photosynthetic tissues of higher plants. Free Radic Biol Med 2018; 122:74-85. [PMID: 29355740 DOI: 10.1016/j.freeradbiomed.2018.01.016] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 01/10/2018] [Accepted: 01/13/2018] [Indexed: 12/11/2022]
Abstract
Organic acids play a crucial role in numerous metabolic processes accompanied by transfer of electrons and protons and linked to the reduction/oxidation of major redox couples in plant cells, such as NAD, NADP, glutathione, and ascorbate. Fluxes through the pathways metabolizing organic acids modulate redox states in cell compartments, contribute to generation of reactive oxygen and nitrogen species, and mediate signal transduction processes. Organic acid metabolism not only functions to equilibrate the redox potential in plant cells but also to transfer redox equivalents between cell compartments supporting various metabolic processes. The most important role in this transfer belongs to different forms of malate dehydrogenase interconverting malate and oxaloacetate or forming pyruvate (malic enzymes). During photosynthesis malate serves as a major form of transfer of redox equivalents from chloroplasts to the cytosol and other compartments via the malate valve. On the other hand, mitochondria, via alterations of their redox potential, become a source of citrate that can be transported to the cytosol and support biosynthesis of amino acids. Citrate is also an important retrograde signalling compound that regulates transcription of several genes including those encoding the alternative oxidase. The alternative oxidase, which is activated by increased redox potential and by pyruvate, is, in turn, important for the maintenance of redox potential in mitochondria. The roles of organic acids in establishing redox equilibrium, supporting ionic gradients on membranes, acidification of the extracellular medium, and regulation of production of reactive oxygen and nitrogen species are discussed.
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Affiliation(s)
- Abir U Igamberdiev
- Department of Biology, Memorial University of Newfoundland, St. John's, NL, Canada A1B 3X9.
| | - Natalia V Bykova
- Morden Research and Development Centre, Agriculture and Agri-Food Canada, Morden, MB, Canada R6M 1Y5
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8
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Eprintsev AT, Falaleeva MI, Lyashchenko MS, Toropygin IY, Igamberdiev AU. Oligomeric forms of bacterial malate dehydrogenase: a study of the enzyme from the phototrophic non-sulfur bacterium Rhodovulum steppense A-20s. Biosci Biotechnol Biochem 2018; 82:81-89. [PMID: 29297253 DOI: 10.1080/09168451.2017.1411776] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Malate dehydrogenase (EC 1.1.1.37) was purified to homogeneity from the phototrophic purple non-sulfur bacterium Rhodovulum steppense A-20s. According to gel-chromatography and electrophoretic studies, malate dehydrogenase is present as a dimer, tetramer and octamer depending on cultivation conditions. In phototrophic aerobic conditions only the tetrameric form was present, in chemotrophic aerobic conditions all three forms were detected, while in the absence of oxygen the octameric form disappeared. The malate dehydrogenase oligomers are encoded by a single gene and composed of the same 35 kDa polypeptide but differ in pH and temperature optimum, in affinities to malate, oxaloacetate, NADH and NAD+ and in regulation by cations and citrate. By modulating the cultivation conditions, it has been established that the dimer participates in the glyoxylate cycle; the tetramer operates in the tricarboxylic acid cycle, and the octamer may be involved in the adaptation to oxidative stress.
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Affiliation(s)
- Alexander T Eprintsev
- a Department of Biochemistry and Cell Physiology , Voronezh State University , Voronezh , Russia
| | - Marina I Falaleeva
- a Department of Biochemistry and Cell Physiology , Voronezh State University , Voronezh , Russia
| | - Maya S Lyashchenko
- a Department of Biochemistry and Cell Physiology , Voronezh State University , Voronezh , Russia
| | - Ilya Y Toropygin
- b V.I. Orekhovich Research Institute of Biomedical Chemistry , Moscow , Russia
| | - Abir U Igamberdiev
- c Department of Biology , Memorial University of Newfoundland , St. John's , Canada
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Transcriptomic and proteomic analyses of leaves from Clematis terniflora DC. under high level of ultraviolet-B irradiation followed by dark treatment. J Proteomics 2017; 150:323-340. [DOI: 10.1016/j.jprot.2016.10.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 09/30/2016] [Accepted: 10/09/2016] [Indexed: 01/09/2023]
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Gardeström P, Igamberdiev AU. The origin of cytosolic ATP in photosynthetic cells. PHYSIOLOGIA PLANTARUM 2016; 157:367-79. [PMID: 27087668 DOI: 10.1111/ppl.12455] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 03/22/2016] [Accepted: 03/24/2016] [Indexed: 05/02/2023]
Abstract
In photosynthetically active cells, both chloroplasts and mitochondria have the capacity to produce ATP via photophosphorylation and oxidative phosphorylation, respectively. Thus, theoretically, both organelles could provide ATP for the cytosol, but the extent, to which they actually do this, and how the process is regulated, both remain unclear. Most of the evidence discussed comes from experiments with rapid fractionation of isolated protoplasts subjected to different treatments in combination with application of specific inhibitors. The results obtained indicate that, under conditions where ATP demand for photosynthetic CO2 fixation is sufficiently high, the mitochondria supply the bulk of ATP for the cytosol. In contrast, under stress conditions where CO2 fixation is severely limited, ATP will build up in chloroplasts and it can then be exported to the cytosol, by metabolite shuttle mechanisms. Thus, depending on the conditions, either mitochondria or chloroplasts can supply the bulk of ATP for the cytosol. This supply of ATP is discussed in relation to the idea that mitochondrial functions may be tuned to provide an optimal environment for the chloroplast. By balancing cellular redox states, mitochondria can contribute to an optimal photosynthetic capacity.
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Affiliation(s)
- Per Gardeström
- Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, Umeå, Sweden
| | - Abir U Igamberdiev
- Department of Biology, Memorial University of Newfoundland, St. John's, Canada
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11
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Eprintsev AT, Fedorin DN, Sazonova OV, Igamberdiev AU. Light inhibition of fumarase in Arabidopsis leaves is phytochrome A-dependent and mediated by calcium. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2016; 102:161-6. [PMID: 26949024 DOI: 10.1016/j.plaphy.2016.02.028] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 02/16/2016] [Accepted: 02/19/2016] [Indexed: 05/19/2023]
Abstract
Inhibition of fumarase activity in the light has been studied in Arabidopsis in relation to the involvement of phytochrome. Using knockout phytochrome mutants, we observed that the main regulator of FUM1 gene transcription, encoding the mitochondrial form of fumarase, is phytochrome A. The active form of phytochrome A suppressed FUM1 expression, while the expression of the FUM2 gene encoding the cytosolic form of fumarase was unaffected both in darkness and in light. The nuclear concentration of Ca(2+) was modulated by red and far-red light. We suggest that the signal transduction mechanism operates via Ca(2+) activation of expression of the gene encoding the transcription factor PIF3, which binds to promoters of phytochrome-regulated genes and inhibits FUM1 expression.
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Affiliation(s)
- Alexander T Eprintsev
- Department of Biochemistry and Cell Physiology, Voronezh State University, 394006 Voronezh, Russia
| | - Dmitry N Fedorin
- Department of Biochemistry and Cell Physiology, Voronezh State University, 394006 Voronezh, Russia
| | - Oksana V Sazonova
- Department of Biochemistry and Cell Physiology, Voronezh State University, 394006 Voronezh, Russia
| | - Abir U Igamberdiev
- Department of Biology, Memorial University of Newfoundland, St. John's, NL A1B 3X9, Canada.
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12
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Figueroa CM, Feil R, Ishihara H, Watanabe M, Kölling K, Krause U, Höhne M, Encke B, Plaxton WC, Zeeman SC, Li Z, Schulze WX, Hoefgen R, Stitt M, Lunn JE. Trehalose 6-phosphate coordinates organic and amino acid metabolism with carbon availability. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2016; 85:410-23. [PMID: 26714615 DOI: 10.1111/tpj.13114] [Citation(s) in RCA: 118] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Revised: 12/14/2015] [Accepted: 12/21/2015] [Indexed: 05/18/2023]
Abstract
Trehalose 6-phosphate (Tre6P) is an essential signal metabolite in plants, linking growth and development to carbon metabolism. The sucrose-Tre6P nexus model postulates that Tre6P acts as both a signal and negative feedback regulator of sucrose levels. To test this model, short-term metabolic responses to induced increases in Tre6P levels were investigated in Arabidopsis thaliana plants expressing the Escherichia coli Tre6P synthase gene (otsA) under the control of an ethanol-inducible promoter. Increased Tre6P levels led to a transient decrease in sucrose content, post-translational activation of nitrate reductase and phosphoenolpyruvate carboxylase, and increased levels of organic and amino acids. Radio-isotope ((14)CO2) and stable isotope ((13)CO2) labelling experiments showed no change in the rates of photoassimilate export in plants with elevated Tre6P, but increased labelling of organic acids. We conclude that high Tre6P levels decrease sucrose levels by stimulating nitrate assimilation and anaplerotic synthesis of organic acids, thereby diverting photoassimilates away from sucrose to generate carbon skeletons and fixed nitrogen for amino acid synthesis. These results are consistent with the sucrose-Tre6P nexus model, and implicate Tre6P in coordinating carbon and nitrogen metabolism in plants.
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Affiliation(s)
- Carlos M Figueroa
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany
| | - Regina Feil
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany
| | - Hirofumi Ishihara
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany
| | - Mutsumi Watanabe
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany
| | - Katharina Kölling
- Department of Biology, Institute of Agricultural Sciences, ETH Zurich, Zurich, 8092, Switzerland
| | - Ursula Krause
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany
| | - Melanie Höhne
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany
| | - Beatrice Encke
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany
| | - William C Plaxton
- Department of Biology and Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, K7L 3N6, Canada
| | - Samuel C Zeeman
- Department of Biology, Institute of Agricultural Sciences, ETH Zurich, Zurich, 8092, Switzerland
| | - Zhi Li
- Department of Plant Systems Biology, University of Hohenheim, Stuttgart, 70593, Germany
| | - Waltraud X Schulze
- Department of Plant Systems Biology, University of Hohenheim, Stuttgart, 70593, Germany
| | - Rainer Hoefgen
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany
| | - Mark Stitt
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany
| | - John E Lunn
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany
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Igamberdiev AU, Eprintsev AT. Organic Acids: The Pools of Fixed Carbon Involved in Redox Regulation and Energy Balance in Higher Plants. FRONTIERS IN PLANT SCIENCE 2016; 7:1042. [PMID: 27471516 PMCID: PMC4945632 DOI: 10.3389/fpls.2016.01042] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 07/04/2016] [Indexed: 05/18/2023]
Abstract
Organic acids are synthesized in plants as a result of the incomplete oxidation of photosynthetic products and represent the stored pools of fixed carbon accumulated due to different transient times of conversion of carbon compounds in metabolic pathways. When redox level in the cell increases, e.g., in conditions of active photosynthesis, the tricarboxylic acid (TCA) cycle in mitochondria is transformed to a partial cycle supplying citrate for the synthesis of 2-oxoglutarate and glutamate (citrate valve), while malate is accumulated and participates in the redox balance in different cell compartments (via malate valve). This results in malate and citrate frequently being the most accumulated acids in plants. However, the intensity of reactions linked to the conversion of these compounds can cause preferential accumulation of other organic acids, e.g., fumarate or isocitrate, in higher concentrations than malate and citrate. The secondary reactions, associated with the central metabolic pathways, in particularly with the TCA cycle, result in accumulation of other organic acids that are derived from the intermediates of the cycle. They form the additional pools of fixed carbon and stabilize the TCA cycle. Trans-aconitate is formed from citrate or cis-aconitate, accumulation of hydroxycitrate can be linked to metabolism of 2-oxoglutarate, while 4-hydroxy-2-oxoglutarate can be formed from pyruvate and glyoxylate. Glyoxylate, a product of either glycolate oxidase or isocitrate lyase, can be converted to oxalate. Malonate is accumulated at high concentrations in legume plants. Organic acids play a role in plants in providing redox equilibrium, supporting ionic gradients on membranes, and acidification of the extracellular medium.
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Affiliation(s)
- Abir U. Igamberdiev
- Department of Biology, Memorial University of Newfoundland, St. John’sNL, Canada
- *Correspondence: Abir U. Igamberdiev,
| | - Alexander T. Eprintsev
- Department of Biochemistry and Cell Physiology, Voronezh State UniversityVoronezh, Russia
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14
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Igamberdiev AU, Kleczkowski LA. Optimization of ATP synthase function in mitochondria and chloroplasts via the adenylate kinase equilibrium. FRONTIERS IN PLANT SCIENCE 2015; 6:10. [PMID: 25674099 PMCID: PMC4309032 DOI: 10.3389/fpls.2015.00010] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 01/06/2015] [Indexed: 05/09/2023]
Abstract
The bulk of ATP synthesis in plants is performed by ATP synthase, the main bioenergetics engine of cells, operating both in mitochondria and in chloroplasts. The reaction mechanism of ATP synthase has been studied in detail for over half a century; however, its optimal performance depends also on the steady delivery of ATP synthase substrates and the removal of its products. For mitochondrial ATP synthase, we analyze here the provision of stable conditions for (i) the supply of ADP and Mg(2+), supported by adenylate kinase (AK) equilibrium in the intermembrane space, (ii) the supply of phosphate via membrane transporter in symport with H(+), and (iii) the conditions of outflow of ATP by adenylate transporter carrying out the exchange of free adenylates. We also show that, in chloroplasts, AK equilibrates adenylates and governs Mg(2+) contents in the stroma, optimizing ATP synthase and Calvin cycle operation, and affecting the import of inorganic phosphate in exchange with triose phosphates. It is argued that chemiosmosis is not the sole component of ATP synthase performance, which also depends on AK-mediated equilibrium of adenylates and Mg(2+), adenylate transport, and phosphate release and supply.
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Affiliation(s)
- Abir U. Igamberdiev
- Department of Biology, Memorial University of Newfoundland, St. John’s, NL, Canada
- *Correspondence: Abir U. Igamberdiev, Department of Biology, Memorial University of Newfoundland, St. John’s, NL A1B3X9, Canada e-mail:
| | - Leszek A. Kleczkowski
- Department of Plant Physiology, Umeå Plant Science Centre, University of Umeå, Umeå, Sweden
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Igamberdiev AU. Control of Rubisco function via homeostatic equilibration of CO2 supply. FRONTIERS IN PLANT SCIENCE 2015; 6:106. [PMID: 25767475 PMCID: PMC4341507 DOI: 10.3389/fpls.2015.00106] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 02/09/2015] [Indexed: 05/09/2023]
Abstract
Rubisco is the most abundant protein on Earth that serves as the primary engine of carbon assimilation. It is characterized by a slow rate and low specificity for CO2 leading to photorespiration. We analyze here the challenges of operation of this enzyme as the main carbon fixation engine. The high concentration of Rubisco exceeds that of its substrate CO2 by 2-3 orders of magnitude; however, the total pool of available carbon in chloroplast, i.e., mainly bicarbonate, is comparable to the concentration of Rubisco active sites. This makes the reactant stationary assumption (RSA), which is essential as a condition of satisfying the Michaelis-Menten (MM) kinetics, valid if we assume that the delivery of CO2 from this pool is not limiting. The RSA is supported by active carbonic anhydrases (CA) that quickly equilibrate bicarbonate and CO2 pools and supply CO2 to Rubisco. While the operation of stromal CA is independent of light reactions, the thylakoidal CA associated with PSII and pumping CO2 from the thylakoid lumen is coordinated with the rate of electron transport, water splitting and proton gradient across the thylakoid membrane. At high CO2 concentrations, CA becomes less efficient (the equilibrium becomes unfavorable), so a deviation from the MM kinetics is observed, consistent with Rubisco reaching its Vmax at approximately 50% lower level than expected from the classical MM curve. Previously, this deviation was controversially explained by the limitation of RuBP regeneration. At low ambient CO2 and correspondingly limited capacity of the bicarbonate pool, its depletion at Rubisco sites is relieved in that the enzyme utilizes O2 instead of CO2, i.e., by photorespiration. In this process, CO2 is supplied back to Rubisco, and the chloroplastic redox state and energy level are maintained. It is concluded that the optimal performance of photosynthesis is achieved via the provision of continuous CO2 supply to Rubisco by carbonic anhydrases and photorespiration.
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Affiliation(s)
- Abir U. Igamberdiev
- *Correspondence: Abir U. Igamberdiev, Department of Biology, Memorial University of Newfoundland, 232 Elizabeth Avenue, St. John’s, NL A1B 3X9, Canada
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Ma YH, Wang X, Niu YF, Yang ZK, Zhang MH, Wang ZM, Yang WD, Liu JS, Li HY. Antisense knockdown of pyruvate dehydrogenase kinase promotes the neutral lipid accumulation in the diatom Phaeodactylum tricornutum. Microb Cell Fact 2014; 13:100. [PMID: 25106441 PMCID: PMC4251698 DOI: 10.1186/s12934-014-0100-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Accepted: 07/03/2014] [Indexed: 11/16/2022] Open
Abstract
Background Microalgae have been an emerging biofuel resource; however, the germplasm improvement has been slow due to the lack of molecular tools. Pyruvate dehydrogenase kinase (PDK) deactivates the pyruvate dehydrogenase complex (PDC) which catalyzes the oxidative decarboxylation of pyruvate. Acetyl-CoA production via PDC is important in plant tissues that are active in fatty acid synthesis. Results A 1261-bp cDNA of a putative PDK gene (PtPDK) was cloned from a diatom Phaeodactylum tricornutum, and PtPDK antisense knockdown transgenic diatoms were generated. Both PtPDK transcript abundance and enzyme activity were reduced significantly due to antisense knockdown of PtPDK. Neutral lipid content of transgenic diatom cells increased up to 82% as determined by Nile red staining, and fatty acid composition was not altered. Transgenic cells showed slightly lower growth rate but similar cell size with the wild type, hence retaining similar biomass productivity. Conclusions This work first obtained a successful engineered diatom regulating a key gene involved in lipid metabolism. Our findings also provide powerful indications in enhancing microalgal lipid production by metabolic engineering for biofuel industry.
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