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de Lorenzo L, Stack TMM, Fox KM, Walstrom KM. Catalytic mechanism and kinetics of malate dehydrogenase. Essays Biochem 2024; 68:73-82. [PMID: 38721782 DOI: 10.1042/ebc20230086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Revised: 04/20/2024] [Accepted: 04/23/2024] [Indexed: 10/04/2024]
Abstract
Malate dehydrogenase (MDH) is a ubiquitous and central enzyme in cellular metabolism, found in all kingdoms of life, where it plays vital roles in the cytoplasm and various organelles. It catalyzes the reversible NAD+-dependent reduction of L-malate to oxaloacetate. This review describes the reaction mechanism for MDH and the effects of mutations in and around the active site on catalytic activity and substrate specificity, with a particular focus on the loop that encloses the active site after the substrates have bound. While MDH exhibits selectivity for its preferred substrates, mutations can alter the specificity of MDH for each cosubstrate. The kinetic characteristics and similarities of a variety of MDH isozymes are summarized, and they illustrate that the KM values are consistent with the relative concentrations of the substrates in cells. As a result of its existence in different cellular environments, MDH properties vary, making it an attractive model enzyme for studying enzyme activity and structure under different conditions.
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Affiliation(s)
- Laura de Lorenzo
- Department of Biochemistry and Molecular Biology, University of New Mexico, School of Medicine, Albuquerque, NM, U.S.A
| | - Tyler M M Stack
- Department of Chemistry and Biochemistry, Providence College, Providence, RI, U.S.A
| | - Kristin M Fox
- Department of Chemistry, Union College, Schenectady, NY, U.S.A
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2
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Cosse M, Rehders T, Eirich J, Finkemeier I, Selinski J. Cysteine oxidation as a regulatory mechanism of Arabidopsis plastidial NAD-dependent malate dehydrogenase. PHYSIOLOGIA PLANTARUM 2024; 176:e14340. [PMID: 38741259 DOI: 10.1111/ppl.14340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Revised: 04/16/2024] [Accepted: 04/23/2024] [Indexed: 05/16/2024]
Abstract
Malate dehydrogenases (MDHs) catalyze a reversible NAD(P)-dependent-oxidoreductase reaction that plays an important role in central metabolism and redox homeostasis of plant cells. Recent studies suggest a moonlighting function of plastidial NAD-dependent MDH (plNAD-MDH; EC 1.1.1.37) in plastid biogenesis, independent of its enzyme activity. In this study, redox effects on activity and conformation of recombinant plNAD-MDH from Arabidopsis thaliana were investigated. We show that reduced plNAD-MDH is active while it is inhibited upon oxidation. Interestingly, the presence of its cofactors NAD+ and NADH could prevent oxidative inhibition of plNAD-MDH. In addition, a conformational change upon oxidation could be observed via non-reducing SDS-PAGE. Both effects, its inhibition and conformational change, were reversible by re-reduction. Further investigation of single cysteine substitutions and mass spectrometry revealed that oxidation of plNAD-MDH leads to oxidation of all four cysteine residues. However, cysteine oxidation of C129 leads to inhibition of plNAD-MDH activity and oxidation of C147 induces its conformational change. In contrast, oxidation of C190 and C333 does not affect plNAD-MDH activity or structure. Our results demonstrate that plNAD-MDH activity can be reversibly inhibited, but not inactivated, by cysteine oxidation and might be co-regulated by the availability of its cofactors in vivo.
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Affiliation(s)
- Maike Cosse
- Plant Cell Biology, Botanical Institute, Christian-Albrechts University, Kiel, Germany
| | - Tanja Rehders
- Plant Cell Biology, Botanical Institute, Christian-Albrechts University, Kiel, Germany
| | - Jürgen Eirich
- Plant Physiology, Institute of Plant Biology and Biotechnology, University of Muenster, Muenster, Germany
| | - Iris Finkemeier
- Plant Physiology, Institute of Plant Biology and Biotechnology, University of Muenster, Muenster, Germany
| | - Jennifer Selinski
- Plant Cell Biology, Botanical Institute, Christian-Albrechts University, Kiel, Germany
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3
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Dao O, Kuhnert F, Weber APM, Peltier G, Li-Beisson Y. Physiological functions of malate shuttles in plants and algae. TRENDS IN PLANT SCIENCE 2022; 27:488-501. [PMID: 34848143 DOI: 10.1016/j.tplants.2021.11.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2021] [Revised: 11/02/2021] [Accepted: 11/04/2021] [Indexed: 06/13/2023]
Abstract
Subcellular compartmentalization confers evolutionary advantage to eukaryotic cells but entails the need for efficient interorganelle communication. Malate functions as redox carrier and metabolic intermediate. It can be shuttled across membranes through translocators. The interconversion of malate and oxaloacetate mediated by malate dehydrogenases requires oxidation/reduction of NAD(P)H/NAD(P)+; therefore, malate trafficking serves to transport reducing equivalents and this is termed the 'malate shuttle'. Although the term 'malate shuttle' was coined more than 50 years ago, novel functions are still emerging. This review highlights recent findings on the functions of malate shuttles in photorespiration, fatty acid β-oxidation, interorganelle signaling and its putative role in CO2-concentrating mechanisms. We compare and contrast knowledge in plants and algae, thereby providing an evolutionary perspective on redox trafficking in photosynthetic eukaryotes.
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Affiliation(s)
- Ousmane Dao
- Aix Marseille Univ, CEA, CNRS, BIAM, Institut de Biosciences et Biotechnologies Aix-Marseille, CEA Cadarache, Saint Paul-Lez-Durance 13108, France
| | - Franziska Kuhnert
- Institute of Plant Biochemistry, Cluster of Excellence on Plant Science (CEPLAS), Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Andreas P M Weber
- Institute of Plant Biochemistry, Cluster of Excellence on Plant Science (CEPLAS), Heinrich Heine University, 40225 Düsseldorf, Germany
| | - Gilles Peltier
- Aix Marseille Univ, CEA, CNRS, BIAM, Institut de Biosciences et Biotechnologies Aix-Marseille, CEA Cadarache, Saint Paul-Lez-Durance 13108, France
| | - Yonghua Li-Beisson
- Aix Marseille Univ, CEA, CNRS, BIAM, Institut de Biosciences et Biotechnologies Aix-Marseille, CEA Cadarache, Saint Paul-Lez-Durance 13108, France.
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Höhner R, Day PM, Zimmermann SE, Lopez LS, Krämer M, Giavalisco P, Correa Galvis V, Armbruster U, Schöttler MA, Jahns P, Krueger S, Kunz HH. Stromal NADH supplied by PHOSPHOGLYCERATE DEHYDROGENASE3 is crucial for photosynthetic performance. PLANT PHYSIOLOGY 2021; 186:142-167. [PMID: 33779763 PMCID: PMC8154072 DOI: 10.1093/plphys/kiaa117] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 12/17/2020] [Indexed: 05/22/2023]
Abstract
During photosynthesis, electrons travel from light-excited chlorophyll molecules along the electron transport chain to the final electron acceptor nicotinamide adenine dinucleotide phosphate (NADP) to form NADPH, which fuels the Calvin-Benson-Bassham cycle (CBBC). To allow photosynthetic reactions to occur flawlessly, a constant resupply of the acceptor NADP is mandatory. Several known stromal mechanisms aid in balancing the redox poise, but none of them utilizes the structurally highly similar coenzyme NAD(H). Using Arabidopsis (Arabidopsis thaliana) as a C3-model, we describe a pathway that employs the stromal enzyme PHOSPHOGLYCERATE DEHYDROGENASE 3 (PGDH3). We showed that PGDH3 exerts high NAD(H)-specificity and is active in photosynthesizing chloroplasts. PGDH3 withdrew its substrate 3-PGA directly from the CBBC. As a result, electrons become diverted from NADPH via the CBBC into the separate NADH redox pool. pgdh3 loss-of-function mutants revealed an overreduced NADP(H) redox pool but a more oxidized plastid NAD(H) pool compared to wild-type plants. As a result, photosystem I acceptor side limitation increased in pgdh3. Furthermore, pgdh3 plants displayed delayed CBBC activation, changes in nonphotochemical quenching, and altered proton motive force partitioning. Our fluctuating light-stress phenotyping data showed progressing photosystem II damage in pgdh3 mutants, emphasizing the significance of PGDH3 for plant performance under natural light environments. In summary, this study reveals an NAD(H)-specific mechanism in the stroma that aids in balancing the chloroplast redox poise. Consequently, the stromal NAD(H) pool may provide a promising target to manipulate plant photosynthesis.
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Affiliation(s)
- Ricarda Höhner
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
| | - Philip M Day
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
| | - Sandra E Zimmermann
- Biocenter University of Cologne, Institute for Plant Science, Cologne 50674, Germany
| | - Laura S Lopez
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
| | - Moritz Krämer
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
| | | | - Viviana Correa Galvis
- Max Planck Institute of Molecular Plant Physiology, Wissenschaftspark Golm, Potsdam 14476, Germany
| | - Ute Armbruster
- Max Planck Institute of Molecular Plant Physiology, Wissenschaftspark Golm, Potsdam 14476, Germany
| | - Mark Aurel Schöttler
- Max Planck Institute of Molecular Plant Physiology, Wissenschaftspark Golm, Potsdam 14476, Germany
| | - Peter Jahns
- Plant Biochemistry, Heinrich-Heine-University Düsseldorf, Düsseldorf D-40225, Germany
| | - Stephan Krueger
- Biocenter University of Cologne, Institute for Plant Science, Cologne 50674, Germany
| | - Hans-Henning Kunz
- School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
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Sun T, Yuan H, Chen C, Kadirjan-Kalbach DK, Mazourek M, Osteryoung KW, Li L. OR His, a Natural Variant of OR, Specifically Interacts with Plastid Division Factor ARC3 to Regulate Chromoplast Number and Carotenoid Accumulation. MOLECULAR PLANT 2020; 13:864-878. [PMID: 32222485 DOI: 10.1016/j.molp.2020.03.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 03/19/2020] [Accepted: 03/20/2020] [Indexed: 05/19/2023]
Abstract
Chromoplasts are colored plastids that synthesize and store massive amounts of carotenoids. Chromoplast number and size define the sink strength for carotenoid accumulation in plants. However, nothing is known about the mechanisms controlling chromoplast number. Previously, a natural allele of Orange (OR), ORHis, was found to promote carotenoid accumulation by activating chromoplast differentiation and increasing carotenoid biosynthesis, but cells in orange tissues in melon fruit and cauliflower OR mutant have only one or two enlarged chromoplasts. In this study, we investigated an ORHis variant of Arabidopsis OR, genetically mimicking the melon ORHis allele, and found that it also constrains chromoplast number in Arabidopsis calli. Both in vitro and in vivo experiments demonstrate that ORHis specifically interacts with the Membrane Occupation and Recognition Nexus domain of ACCUMULATION AND REPLICATION OF CHLOROPLASTS 3 (ARC3), a crucial regulator of chloroplast division. We further showed that ORHis interferes with the interaction between ARC3 and PARALOG OF ARC6 (PARC6), another key regulator of chloroplast division, suggesting a role of ORHis in competing with PARC6 for binding to ARC3 to restrict chromoplast number. Overexpression or knockout of ARC3 in Arabidopsis ORHis plants significantly alters total carotenoid levels. Moreover, overexpression of the plastid division factor PLASTID DIVISION 1 greatly enhances carotenoid accumulation. These division factors likely alter carotenoid levels via their influence on chromoplast number and/or size. Taken together, our findings provide novel mechanistic insights into the machinery controlling chromoplast number and highlight a potential new strategy for enhancing carotenoid accumulation and nutritional value in food crops.
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Affiliation(s)
- Tianhu Sun
- Robert W. Holley Center for Agriculture and Health, USDA-ARS, Cornell University, Ithaca, NY 14853, USA; Plant Breeding and Genetics Section, School of Integrative Plant Science, Cornell University, Ithaca, NY 14853, USA
| | - Hui Yuan
- Robert W. Holley Center for Agriculture and Health, USDA-ARS, Cornell University, Ithaca, NY 14853, USA; Plant Breeding and Genetics Section, School of Integrative Plant Science, Cornell University, Ithaca, NY 14853, USA
| | - Cheng Chen
- Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA
| | | | - Michael Mazourek
- Plant Breeding and Genetics Section, School of Integrative Plant Science, Cornell University, Ithaca, NY 14853, USA
| | | | - Li Li
- Robert W. Holley Center for Agriculture and Health, USDA-ARS, Cornell University, Ithaca, NY 14853, USA; Plant Breeding and Genetics Section, School of Integrative Plant Science, Cornell University, Ithaca, NY 14853, USA.
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Yu L, Zhang Y, Li M, Wang C, Lin X, Li L, Shi X, Guo C, Lin S. Comparative metatranscriptomic profiling and microRNA sequencing to reveal active metabolic pathways associated with a dinoflagellate bloom. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 699:134323. [PMID: 31522044 DOI: 10.1016/j.scitotenv.2019.134323] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 09/05/2019] [Accepted: 09/05/2019] [Indexed: 06/10/2023]
Abstract
Harmful algal blooms (HABs) have increased as a result of global climate and environmental changes, exerting increasing impacts on the aquatic ecosystem, coastal economy, and human health. Despite great research efforts, our understanding on the drivers of HABs is still limited in part because HAB species' physiology is difficult to probe in situ. Here, we used molecular ecological analyses to characterize a dinoflagellate bloom at Xiamen Harbor, China. Prorocentrum donghaiense was identified as the culprit, which nutrient bioassays showed were not nutrient-limited. Metatranscriptome profiling revealed that P. donghaiense highly expressed genes related to N- and P-nutrient uptake, phagotrophy, energy metabolism (photosynthesis, oxidative phophorylation, and rhodopsin) and carbohydrate metabolism (glycolysis/gluconeogenesis, TCA cycle and pentose phosphate) during the bloom. Many genes in P. donghaiense were up-regulated at night, including phagotrophy and environmental communication genes, and showed active expression in mitosis. Eight microbial defense genes were up-regulated in the bloom compared with previously analyzed laboratory cultures. Furthermore, 76 P. donghaiense microRNA were identified from the bloom, and their target genes exhibited marked differences in amino acid metabolism between the bloom and cultures and the potential of up-regulated antibiotic and cell communication capabilities. These findings, consistent with and complementary to recent reports, reveal major metabolic processes in P. donghaiense potentially important for bloom formation and provide a gene repertoire for developing bloom markers in future research.
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Affiliation(s)
- Liying Yu
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
| | - Yaqun Zhang
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China; Key Laboratory of Aquatic Genomics, Ministry of Agriculture and Rural Affairs, CAFS Key Laboratory of Aquatic Genomics and Beijing Key Laboratory of Fishery Biotechnology, Chinese Academy of Fishery Sciences, Beijing 100141, China
| | - Meizhen Li
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
| | - Cong Wang
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
| | - Xin Lin
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
| | - Ling Li
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
| | - Xinguo Shi
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China; College of Biological Science and Engineering, Fuzhou University, Fujian 350116, China
| | - Chentao Guo
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
| | - Senjie Lin
- State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China; Department of Marine Sciences, University of Connecticut, Groton, CT 06340, USA.
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Zhang C, Li H, Yuan C, Liu S, Li M, Zhu J, Lin X, Lu Y, Guo X. CKB1 regulates expression of ribosomal protein L10 family gene and plays a role in UV-B response. PLANT BIOLOGY (STUTTGART, GERMANY) 2020; 22 Suppl 1:143-152. [PMID: 30597713 DOI: 10.1111/plb.12954] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Accepted: 12/22/2018] [Indexed: 06/09/2023]
Abstract
Plastid casein kinase 2 (CK2), which is a major Ser/Thr-specific enzyme in higher organisms, plays an essential role in plant development and diverse abiotic stresses. CKB1 is a regulatory subunit beta of CK2. To expand our understand of functions of the CKB1 gene in Arabidopsis thaliana, protein changes among wild-type (WT) and CKB1 gain- and loss-of-function mutants were compared. Proteins extracted from the CKB1 knockout mutant and overexpressing mutant were compared with Col-0 plants using 2D-PAGE. Proteins regulated by CKB1 were identified with matrix-assisted laser desorption ionisation time-of-flight/time-of-flight mass spectrometry (MALDI-TOF/TOF), and its transcript was verified by qRT-PCR. Bioinformatics analysis, including gene ontology and protein-protein interaction analysis, were employed. The results of mass spectra and bioinformatics analysis suggest that CKB1 may have functions in regulation of the ribosomal protein L10 (RPL10) family and is involved in ultraviolet-B (UV-B) response. Furthermore, qRT-PCR verification showed CKB1 expression was up-regulated by UV-B stress. The expression levels of five genes in the RPL10 family were reduced in the ckb1 T-DNA insertion mutants, whereas they increased in the CKB1 overexpressing mutants under both normal conditions and UV-B treatment. In conclusion, CKB1 has important functions in UV-B radiation stress. Our study implies that CKB1 positively regulates UV-B radiation stress signalling, possibly through modulating expression of the RPL10 family.
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Affiliation(s)
- C Zhang
- College of Life Sciences, Hunan University, Changsha, China
| | - H Li
- College of Life Sciences, Hunan University, Changsha, China
| | - C Yuan
- College of Life Sciences, Hunan University, Changsha, China
| | - S Liu
- College of Life Sciences, Hunan University, Changsha, China
| | - M Li
- College of Life Sciences, Hunan University, Changsha, China
| | - J Zhu
- College of Life Sciences, Hunan University, Changsha, China
| | - X Lin
- College of Life Sciences, Hunan University, Changsha, China
| | - Y Lu
- College of Life Sciences, Hunan University, Changsha, China
| | - X Guo
- College of Life Sciences, Hunan University, Changsha, China
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8
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Direct recovery of malate dehydrogenase from highly turbid yeast cell homogenate using dye-ligand affinity chromatography in stirred fluidized bed. J Chromatogr B Analyt Technol Biomed Life Sci 2018; 1100-1101:65-75. [DOI: 10.1016/j.jchromb.2018.09.039] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2018] [Revised: 09/20/2018] [Accepted: 09/28/2018] [Indexed: 11/22/2022]
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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: 41] [Impact Index Per Article: 6.8] [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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10
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de Freitas-Silva L, Rodríguez-Ruiz M, Houmani H, da Silva LC, Palma JM, Corpas FJ. Glyphosate-induced oxidative stress in Arabidopsis thaliana affecting peroxisomal metabolism and triggers activity in the oxidative phase of the pentose phosphate pathway (OxPPP) involved in NADPH generation. JOURNAL OF PLANT PHYSIOLOGY 2017; 218:196-205. [PMID: 28888161 DOI: 10.1016/j.jplph.2017.08.007] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Revised: 06/27/2017] [Accepted: 08/11/2017] [Indexed: 06/07/2023]
Abstract
Glyphosate is a broad-spectrum systemic herbicide used worldwide. In susceptible plants, glyphosate affects the shikimate pathway and reduces aromatic amino acid synthesis. Using Arabidopsis seedlings grown in the presence of 20μM glyphosate, we analyzed H2O2, ascorbate, glutathione (GSH) and protein oxidation content as well as antioxidant catalase, superoxide dismutase (SOD) and ascorbate-glutathione cycle enzyme activity. We also examined the principal NADPH-generating system components, including glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH), NADP-malic enzyme (NADP-ME) and NADP-isocitrate dehydrogenase (NADP-ICDH). Glyphosate caused a drastic reduction in growth parameters and an increase in protein oxidation. The herbicide also resulted in an overall increase in GSH content, antioxidant enzyme activity (catalase and all enzymatic components of the ascorbate-glutathione cycle) in addition to the two oxidative phase enzymes, G6PDH and 6PGDH, in the pentose phosphate pathway involved in NADPH generation. In this study, we provide new evidence on the participation of G6PDH and 6PGDH in the response to oxidative stress induced by glyphosate in Arabidopsis, in which peroxisomal enzymes, such as catalase and glycolate oxidase, are positively affected. We suggest that the NADPH provided by the oxidative phase of the pentose phosphate pathway (OxPPP) should serve to maintain glutathione reductase (GR) activity, thus preserving and regenerating the intracellular GSH pool under glyphosate-induced stress. It is particularly remarkable that the 6PGDH activity was unaffected by pro-oxidant and nitrating molecules such as H202, nitric oxide or peroxynitrite.
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Affiliation(s)
- Larisse de Freitas-Silva
- Departamento de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, CSIC, Granada, Spain; Universidade Federal de Viçosa, 36570-900 Viçosa, MG, Brazil
| | - Marta Rodríguez-Ruiz
- Departamento de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, CSIC, Granada, Spain
| | - Hayet Houmani
- Departamento de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, CSIC, Granada, Spain
| | | | - José M Palma
- Departamento de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, CSIC, Granada, Spain
| | - Francisco J Corpas
- Departamento de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, CSIC, Granada, Spain.
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