501
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Andrade HM, Murta SMF, Chapeaurouge A, Perales J, Nirdé P, Romanha AJ. Proteomic Analysis of Trypanosoma cruzi Resistance to Benznidazole. J Proteome Res 2008; 7:2357-67. [DOI: 10.1021/pr700659m] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hélida M. Andrade
- Laboratório de Parasitologia Celular e Molecular, Centro de Pesquisa René Rachou/FIOCRUZ, Brazil, Universidade Federal do Paiuí, Lab Imunogenética e Biologia Molecular, Teresina, Piauí, Brazil, Laboratório de Toxinologia, Departamento de Fisiologia e Farmacodinâmica, Instituto Oswaldo Cruz/FIOCRUZ, Brazil, and INSERM U540, 60 rue de Navacelles, 34090 Montpellier, France
| | - Silvane M. F. Murta
- Laboratório de Parasitologia Celular e Molecular, Centro de Pesquisa René Rachou/FIOCRUZ, Brazil, Universidade Federal do Paiuí, Lab Imunogenética e Biologia Molecular, Teresina, Piauí, Brazil, Laboratório de Toxinologia, Departamento de Fisiologia e Farmacodinâmica, Instituto Oswaldo Cruz/FIOCRUZ, Brazil, and INSERM U540, 60 rue de Navacelles, 34090 Montpellier, France
| | - Alex Chapeaurouge
- Laboratório de Parasitologia Celular e Molecular, Centro de Pesquisa René Rachou/FIOCRUZ, Brazil, Universidade Federal do Paiuí, Lab Imunogenética e Biologia Molecular, Teresina, Piauí, Brazil, Laboratório de Toxinologia, Departamento de Fisiologia e Farmacodinâmica, Instituto Oswaldo Cruz/FIOCRUZ, Brazil, and INSERM U540, 60 rue de Navacelles, 34090 Montpellier, France
| | - Jonas Perales
- Laboratório de Parasitologia Celular e Molecular, Centro de Pesquisa René Rachou/FIOCRUZ, Brazil, Universidade Federal do Paiuí, Lab Imunogenética e Biologia Molecular, Teresina, Piauí, Brazil, Laboratório de Toxinologia, Departamento de Fisiologia e Farmacodinâmica, Instituto Oswaldo Cruz/FIOCRUZ, Brazil, and INSERM U540, 60 rue de Navacelles, 34090 Montpellier, France
| | - Phillipe Nirdé
- Laboratório de Parasitologia Celular e Molecular, Centro de Pesquisa René Rachou/FIOCRUZ, Brazil, Universidade Federal do Paiuí, Lab Imunogenética e Biologia Molecular, Teresina, Piauí, Brazil, Laboratório de Toxinologia, Departamento de Fisiologia e Farmacodinâmica, Instituto Oswaldo Cruz/FIOCRUZ, Brazil, and INSERM U540, 60 rue de Navacelles, 34090 Montpellier, France
| | - Alvaro J. Romanha
- Laboratório de Parasitologia Celular e Molecular, Centro de Pesquisa René Rachou/FIOCRUZ, Brazil, Universidade Federal do Paiuí, Lab Imunogenética e Biologia Molecular, Teresina, Piauí, Brazil, Laboratório de Toxinologia, Departamento de Fisiologia e Farmacodinâmica, Instituto Oswaldo Cruz/FIOCRUZ, Brazil, and INSERM U540, 60 rue de Navacelles, 34090 Montpellier, France
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502
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Maeda K, Hägglund P, Finnie C, Svensson B, Henriksen A. Crystal structures of barley thioredoxin h isoforms HvTrxh1 and HvTrxh2 reveal features involved in protein recognition and possibly in discriminating the isoform specificity. Protein Sci 2008; 17:1015-24. [PMID: 18424513 DOI: 10.1110/ps.083460308] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
H-type thioredoxins (Trxs) constitute a particularly large Trx sub-group in higher plants. Here, the crystal structures are determined for the two barley Trx h isoforms, HvTrxh1 and HvTrxh2, in the partially radiation-reduced state to resolutions of 1.7 A, and for HvTrxh2 in the oxidized state to 2.0 A. The two Trxs have a sequence identity of 51% and highly similar fold and active-site architecture. Interestingly, the four independent molecules in the crystals of HvTrxh1 form two relatively large and essentially identical protein-protein interfaces. In each interface, a loop segment of one HvTrxh1 molecule is positioned along a shallow hydrophobic groove at the primary nucleophile Cys40 of another HvTrxh1 molecule. The association mode can serve as a model for the target protein recognition by Trx, as it brings the Met82 Cgamma atom (gamma position as a disulfide sulfur) of the bound loop segment in the proximity of the Cys40 thiol. The interaction involves three characteristic backbone-backbone hydrogen bonds in an antiparallel beta-sheet-like arrangement, similar to the arrangement observed in the structure of an engineered, covalently bound complex between Trx and a substrate protein, as reported by Maeda et al. in an earlier paper. The occurrence of an intermolecular salt bridge between Glu80 of the bound loop segment and Arg101 near the hydrophobic groove suggests that charge complementarity plays a role in the specificity of Trx. In HvTrxh2, isoleucine corresponds to this arginine, which emphasizes the potential for specificity differences between the coexisting barley Trx isoforms.
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Affiliation(s)
- Kenji Maeda
- Enzyme and Protein Chemistry, Department of Systems Biology, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
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503
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Bagnaresi P, Moschella A, Beretta O, Vitulli F, Ranalli P, Perata P. Heterologous microarray experiments allow the identification of the early events associated with potato tuber cold sweetening. BMC Genomics 2008; 9:176. [PMID: 18416834 PMCID: PMC2358903 DOI: 10.1186/1471-2164-9-176] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2007] [Accepted: 04/16/2008] [Indexed: 01/21/2023] Open
Abstract
Background Since its discovery more than 100 years ago, potato (Solanum tuberosum) tuber cold-induced sweetening (CIS) has been extensively investigated. Several carbohydrate-associated genes would seem to be involved in the process. However, many uncertainties still exist, as the relative contribution of each gene to the process is often unclear, possibly as the consequence of the heterogeneity of experimental systems. Some enzymes associated with CIS, such as β-amylases and invertases, have still to be identified at a sequence level. In addition, little is known about the early events that trigger CIS and on the involvement/association with CIS of genes different from carbohydrate-associated genes. Many of these uncertainties could be resolved by profiling experiments, but no GeneChip is available for the potato, and the production of the potato cDNA spotted array (TIGR) has recently been discontinued. In order to obtain an overall picture of early transcriptional events associated with CIS, we investigated whether the commercially-available tomato Affymetrix GeneChip could be used to identify which potato cold-responsive gene family members should be further studied in detail by Real-Time (RT)-PCR (qPCR). Results A tomato-potato Global Match File was generated for the interpretation of various aspects of the heterologous dataset, including the retrieval of best matching potato counterparts and annotation, and the establishment of a core set of highly homologous genes. Several cold-responsive genes were identified, and their expression pattern was studied in detail by qPCR over 26 days. We detected biphasic behaviour of mRNA accumulation for carbohydrate-associated genes and our combined GeneChip-qPCR data identified, at a sequence level, enzymatic activities such as β-amylases and invertases previously reported as being involved in CIS. The GeneChip data also unveiled important processes accompanying CIS, such as the induction of redox- and ethylene-associated genes. Conclusion Our Global Match File strategy proved critical for accurately interpretating heterologous datasets, and suggests that similar approaches may be fruitful for other species. Transcript profiling of early events associated with CIS revealed a complex network of events involving sugars, redox and hormone signalling which may be either linked serially or act in parallel. The identification, at a sequence level, of various enzymes long known as having a role in CIS provides molecular tools for further understanding the phenomenon.
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Affiliation(s)
- Paolo Bagnaresi
- CRA-GPG, Genomic Research Center, Via S, Protaso 302, I-29017 Fiorenzuola d'Arda (PC), Italy.
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504
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Müller J, Ley S, Felger I, Hemphill A, Müller N. Identification of differentially expressed genes in a Giardia lamblia WB C6 clone resistant to nitazoxanide and metronidazole. J Antimicrob Chemother 2008; 62:72-82. [PMID: 18408240 DOI: 10.1093/jac/dkn142] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
OBJECTIVES The characterization of differential gene expression in Giardia lamblia WB C6 strain C4 resistant to metronidazole and nitazoxanide using microarray technology and quantitative real-time PCR. METHODS In a previous study, we created and characterized the G. lamblia WB C6 clone C4 resistant to nitazoxanide and metronidazole. In this study, using a microarray-based approach, we have identified open-reading frames (ORFs) that were differentially expressed in C4 when compared with its wild-type WB C6. Using quantitative real-time PCR, we have validated the expression patterns of some of those ORFs, focusing on chaperones such as heat-shock proteins in wild-type and C4 trophozoites. In order to induce an antigenic shift, trophozoites of both strains were subjected to a cycle of en- and excystation. Expression of selected genes and resistance to nitazoxanide and metronidazole were investigated after this cycle. RESULTS Forty of a total of 9115 ORFs were found to be up-regulated and 46 to be down-regulated in C4 when compared with wild-type. After a cycle of en- and excystation, resistance of C4 to nitazoxanide and metronidazole was lost. Resistance formation and en-/excystation were correlated with changes in expression of ORFs encoding for major surface antigens such as the variant surface protein TSA417 or AS7 ('antigenic shift'). Moreover, expression patterns of the cytosolic heat-shock protein HSP70 B2, HSP40, and of the previously identified nitazoxanide-binding proteins nitroreductase and protein disulphide isomerase PDI4 were correlated with resistance and loss of resistance after en-/excystation. C4 trophozoites had a higher thermotolerance level than wild-type trophozoites. After en-/excystation, this tolerance was lost. CONCLUSIONS These results suggest that resistance formation in Giardia to nitazoxanide and metronidazole is correlated with altered expression of genes involved in stress response such as heat-shock proteins.
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Affiliation(s)
- Joachim Müller
- Institute of Parasitology, University of Berne, Länggass-Strasse 122, CH-3012 Berne, Switzerland.
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505
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Oelze ML, Kandlbinder A, Dietz KJ. Redox regulation and overreduction control in the photosynthesizing cell: complexity in redox regulatory networks. Biochim Biophys Acta Gen Subj 2008; 1780:1261-72. [PMID: 18439433 DOI: 10.1016/j.bbagen.2008.03.015] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 03/25/2008] [Accepted: 03/27/2008] [Indexed: 01/07/2023]
Abstract
Regulation of the photosynthetic apparatus between efficient energy conversion at low light and avoidance of overreduction and damage development at excess light resembles dangerous navigating between Scylla and Charybdis. Photosynthesis is a high rate redox metabolic pathway that generates redox intermediates with extreme redox potentials and eventually reactive oxygen species and oxidative stress. Therefore it is not surprising that the states of defined redox reactions in the chloroplast provide the predominant information and thus directly or indirectly the decisive signals for the multilevel control of cell activities in the chloroplast, cytoplasm, mitochondrion and nucleus. This review elaborates on the diversity of photosynthesis-derived redox signals such as the plastoquinone and thiol redox state that regulate and coordinate light use efficiency, electron transport activity, metabolic reactions, gene transcription and translation not only in the chloroplast but through retrograde signaling also essentially in all other cell compartments. The synergistic and antagonistic interrelations between the redox-dependent signaling pathways and their interactions with other signals such as abscisic acid and tetrapyrol intermediates constitute a redundant and probably buffered regulatory network to optimize performance of photosynthesis on the cellular and whole leaf level.
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Affiliation(s)
- Marie-Luise Oelze
- Biochemistry and Physiology of Plants, Faculty of Biology-W5, Bielefeld University, 33501 Bielefeld, Germany
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506
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Fulton DC, Stettler M, Mettler T, Vaughan CK, Li J, Francisco P, Gil M, Reinhold H, Eicke S, Messerli G, Dorken G, Halliday K, Smith AM, Smith SM, Zeeman SC. Beta-AMYLASE4, a noncatalytic protein required for starch breakdown, acts upstream of three active beta-amylases in Arabidopsis chloroplasts. THE PLANT CELL 2008; 20:1040-58. [PMID: 18390594 PMCID: PMC2390740 DOI: 10.1105/tpc.107.056507] [Citation(s) in RCA: 233] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Revised: 02/21/2008] [Accepted: 03/20/2008] [Indexed: 05/17/2023]
Abstract
This work investigated the roles of beta-amylases in the breakdown of leaf starch. Of the nine beta-amylase (BAM)-like proteins encoded in the Arabidopsis thaliana genome, at least four (BAM1, -2, -3, and -4) are chloroplastic. When expressed as recombinant proteins in Escherichia coli, BAM1, BAM2, and BAM3 had measurable beta-amylase activity but BAM4 did not. BAM4 has multiple amino acid substitutions relative to characterized beta-amylases, including one of the two catalytic residues. Modeling predicts major differences between the glucan binding site of BAM4 and those of active beta-amylases. Thus, BAM4 probably lost its catalytic capacity during evolution. Total beta-amylase activity was reduced in leaves of bam1 and bam3 mutants but not in bam2 and bam4 mutants. The bam3 mutant had elevated starch levels and lower nighttime maltose levels than the wild type, whereas bam1 did not. However, the bam1 bam3 double mutant had a more severe phenotype than bam3, suggesting functional overlap between the two proteins. Surprisingly, bam4 mutants had elevated starch levels. Introduction of the bam4 mutation into the bam3 and bam1 bam3 backgrounds further elevated the starch levels in both cases. These data suggest that BAM4 facilitates or regulates starch breakdown and operates independently of BAM1 and BAM3. Together, our findings are consistent with the proposal that beta-amylase is a major enzyme of starch breakdown in leaves, but they reveal unexpected complexity in terms of the specialization of protein function.
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Affiliation(s)
- Daniel C Fulton
- Institute of Molecular Plant Sciences, University of Edinburgh, Edinburgh EH9 3JH, United Kingdom
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507
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Meyer Y, Siala W, Bashandy T, Riondet C, Vignols F, Reichheld JP. Glutaredoxins and thioredoxins in plants. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1783:589-600. [DOI: 10.1016/j.bbamcr.2007.10.017] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2007] [Revised: 10/26/2007] [Accepted: 10/30/2007] [Indexed: 12/22/2022]
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508
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Yoshida K, Watanabe C, Kato Y, Sakamoto W, Noguchi K. Influence of chloroplastic photo-oxidative stress on mitochondrial alternative oxidase capacity and respiratory properties: a case study with Arabidopsis yellow variegated 2. PLANT & CELL PHYSIOLOGY 2008; 49:592-603. [PMID: 18296449 DOI: 10.1093/pcp/pcn031] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [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. Although it has been demonstrated that leaf AOX is up-regulated under high-light (HL) conditions, the in vivo mechanism of AOX up-regulation by light is still unknown. In the present study, we examined whether the photo-oxidative stress in the chloroplast modulates mitochondrial respiratory properties, especially the AOX capacity, using Arabidopsis leaf-variegated mutant yellow variegated 2 (var2) and exposing plants to HL. var2 mutants lack FtsH2 metalloprotease required for the repair of damaged PSII. Indeed, var2-1 suffered from photo-oxidative stress even before the HL treatments. While the activities of tricarboxylic acid cycle enzymes and cytochrome c oxidase in var2-1 were almost identical to those in the wild type, the amount of AOX protein and the CN-resistant respiration rate were higher in var2-1. Real-time PCR analysis revealed that HL treatment induced the expression of some energy-dissipating respiratory genes, including AOX1a, NDB2 and UCP5, more strongly in var2-1. Western blotting using var2-1 leaf extracts specific to green or white sectors, containing functional or non-functional photosynthetic apparatus, respectively, revealed that more AOX protein was induced in the green sectors by the HL treatment. These results indicate that photo-oxidative stress by excess light is involved in the regulation of respiratory gene expression and the modulation of respiratory properties, especially the AOX up-regulation.
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Affiliation(s)
- Keisuke Yoshida
- Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan.
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509
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Bartsch S, Monnet J, Selbach K, Quigley F, Gray J, von Wettstein D, Reinbothe S, Reinbothe C. Three thioredoxin targets in the inner envelope membrane of chloroplasts function in protein import and chlorophyll metabolism. Proc Natl Acad Sci U S A 2008; 105:4933-8. [PMID: 18349143 PMCID: PMC2290756 DOI: 10.1073/pnas.0800378105] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2007] [Indexed: 01/30/2023] Open
Abstract
Thioredoxins (Trxs) are ubiquitous small proteins with a redox-active disulfide bridge. In their reduced form, they constitute very efficient protein disulfide oxidoreductases. In chloroplasts, two types of Trxs (f and m) coexist and play central roles in the regulation of the Calvin cycle and other processes. Here, we identified a class of Trx targets in the inner plastid envelope membrane of chloroplasts that share a CxxC motif approximately 73 aa from their carboxyl-terminal end. Members of this group belong to a superfamily of Rieske iron-sulfur proteins involved in protein translocation and chlorophyll metabolism. These proteins include the protein translocon protein TIC55, the precursor NADPH:protochlorophyllide oxidoreductase translocon protein PTC52, which operates as protochlorophyllide a-oxygenase, and the lethal leaf spot protein LLS1, which is identical with pheophorbide a oxygenase. The role of these proteins in dark/light regulation and oxidative control by the Trx system is discussed.
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Affiliation(s)
- Sandra Bartsch
- *Lehrstuhl für Pflanzenphysiologie, Universität Bayreuth, Universitätsstrasse 30, D-95447 Bayreuth, Germany
| | - Julie Monnet
- Unité Mixte de Recherche 5575, Centre d'Etudes et de Recherches sur les Macromolécules Organiques, Université Joseph Fourier et Centre National de la Recherche Scientifique, BP53, F-38041 Grenoble Cedex 9, France
| | - Kristina Selbach
- Unité Mixte de Recherche 5575, Centre d'Etudes et de Recherches sur les Macromolécules Organiques, Université Joseph Fourier et Centre National de la Recherche Scientifique, BP53, F-38041 Grenoble Cedex 9, France
| | - Françoise Quigley
- Unité Mixte de Recherche 5575, Centre d'Etudes et de Recherches sur les Macromolécules Organiques, Université Joseph Fourier et Centre National de la Recherche Scientifique, BP53, F-38041 Grenoble Cedex 9, France
| | - John Gray
- Department of Biological Sciences, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606; and
| | - Diter von Wettstein
- Department of Crop and Soil Sciences and School of Molecular Biosciences, Washington State University, Pullman WA 99164-6420
| | - Steffen Reinbothe
- Unité Mixte de Recherche 5575, Centre d'Etudes et de Recherches sur les Macromolécules Organiques, Université Joseph Fourier et Centre National de la Recherche Scientifique, BP53, F-38041 Grenoble Cedex 9, France
| | - Christiane Reinbothe
- *Lehrstuhl für Pflanzenphysiologie, Universität Bayreuth, Universitätsstrasse 30, D-95447 Bayreuth, Germany
- Unité Mixte de Recherche 5575, Centre d'Etudes et de Recherches sur les Macromolécules Organiques, Université Joseph Fourier et Centre National de la Recherche Scientifique, BP53, F-38041 Grenoble Cedex 9, France
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510
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Traverso JA, Vignols F, Cazalis R, Serrato AJ, Pulido P, Sahrawy M, Meyer Y, Cejudo FJ, Chueca A. Immunocytochemical localization of Pisum sativum TRXs f and m in non-photosynthetic tissues. JOURNAL OF EXPERIMENTAL BOTANY 2008; 59:1267-77. [PMID: 18356145 DOI: 10.1093/jxb/ern037] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Plants are the organisms containing the most complex multigenic family for thioredoxins (TRX). Several types of TRXs are targeted to chloroplasts, which have been classified into four subgroups: m, f, x, and y. Among them, TRXs f and m were the first plastidial TRXs characterized, and their function as redox modulators of enzymes involved in carbon assimilation in the chloroplast has been well-established. Both TRXs, f and m, were named according to their ability to reduce plastidial fructose-1,6-bisphosphatase (FBPase) and malate dehydrogenase (MDH), respectively. Evidence is presented here based on the immunocytochemistry of the localization of f and m-type TRXs from Pisum sativum in non-photosynthetic tissues. Both TRXs showed a different spatial pattern. Whilst PsTRXm was localized to vascular tissues of all the organs analysed (leaves, stems, and roots), PsTRXf was localized to more specific cells next to xylem vessels and vascular cambium. Heterologous complementation analysis of the yeast mutant EMY63, deficient in both yeast TRXs, by the pea plastidial TRXs suggests that PsTRXm, but not PsTRXf, is involved in the mechanism of reactive oxygen species (ROS) detoxification. In agreement with this function, the PsTRXm gene was induced in roots of pea plants in response to hydrogen peroxide.
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Affiliation(s)
- José A Traverso
- Departamento de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín (CSIC), C/ Prof. Albareda 1, E-18008-Granada, Spain.
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511
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Stengel A, Benz P, Balsera M, Soll J, Bölter B. TIC62 redox-regulated translocon composition and dynamics. J Biol Chem 2008; 283:6656-67. [PMID: 18180301 DOI: 10.1074/jbc.m706719200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The preprotein translocon at the inner envelope of chloroplasts (Tic complex) facilitates the import of nuclear-encoded preproteins into the organelle. Seven distinct subunits have been identified so far. For each of those, specific functions have been proposed based on structural prediction or experimental evidence. Three of those subunits possess modules that could act as redox-active regulatory components in the import process. To date, however, the mode of redox regulation of the import process remains enigmatic. To investigate how the chloroplast redox state influences translocon behavior and composition, we studied the Tic component and the putative redox sensor Tic62 in more detail. The experimental results provide evidence that Tic62 can act as a bona fide dehydrogenase in vitro, and that it changes its localization in the chloroplast dependent on the NADP+/NADPH ratio in the stroma. Moreover, the redox state influences the interactions of Tic62 with the translocon and the flavoenzyme ferredoxin-NADP+ oxidoreductase. Additionally, we give initial experimental insights into the Tic62 structure using circular dichroism measurements and demonstrate that the protein consists of two structurally different domains. Our results indicate that Tic62 possesses redox-dependent properties that would allow it to fulfill a role as redox sensor protein in the chloroplast.
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Affiliation(s)
- Anna Stengel
- Munich Center for Integrated Protein Science CiPS, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, D-81377 Munich, Germany
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512
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Howard TP, Metodiev M, Lloyd JC, Raines CA. Thioredoxin-mediated reversible dissociation of a stromal multiprotein complex in response to changes in light availability. Proc Natl Acad Sci U S A 2008; 105:4056-61. [PMID: 18322016 PMCID: PMC2268787 DOI: 10.1073/pnas.0710518105] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2007] [Indexed: 11/18/2022] Open
Abstract
A Calvin cycle multiprotein complex including phosphoribulokinase (PRK), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and a small protein, CP12, has previously been identified. In this article, we have studied this complex in leaves and have shown that dissociation and reassociation of the PRK/GAPDH/CP12 complex occurs in a time frame of minutes, allowing for rapid regulation of enzyme activity. Furthermore, we have shown that the extent of formation and dissociation of the PRK/GAPDH/CP12 complex correlates with the quantity of light. These data provide evidence linking the status of this complex with the rapid and subtle regulation of GAPDH and PRK activities in response to fluctuations in light availability. We have also demonstrated that dissociation of this complex depends on electron transport chain activity and that the major factor involved in the dissociation of the pea complex was thioredoxin f. We show here that both PRK and GAPDH are present in the reduced form in leaves in the dark, but are inactive, demonstrating the role of the PRK/GAPDH/CP12 complex in deactivating these enzymes in response to reductions in light intensity. Based on our data, we propose a model for thioredoxin f-mediated activation of PRK and GAPDH by two mechanisms: directly through reduction of disulfide bonds within these enzymes and indirectly by mediating the breakdown of the complex in response to changes in light intensity.
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Affiliation(s)
- Thomas P. Howard
- Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, United Kingdom
| | - Metodi Metodiev
- Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, United Kingdom
| | - Julie C. Lloyd
- Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, United Kingdom
| | - Christine A. Raines
- Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, United Kingdom
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513
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Two zinc-cluster transcription factors control induction of alternative oxidase in Neurospora crassa. Genetics 2008; 177:1997-2006. [PMID: 18073419 DOI: 10.1534/genetics.107.078212] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The alternative oxidase transfers electrons from ubiquinol to molecular oxygen, providing a mechanism for bypassing the later steps of the standard cytochrome-mediated electron transport chain. The enzyme is found in an array of organisms and in many cases is known to be produced in response to perturbations of the standard chain. Alternative oxidase is encoded in the nucleus but functions in the inner mitochondrial membrane. This implies the existence of a retrograde regulation pathway for communicating from the mitochondrion to the nucleus to induce alternative oxidase expression. Previous studies on alternative oxidase in fungi and plants have shown that a number of genes are required for expression of the enzyme, but the identity of these genes has remained elusive. By gene rescue we have now shown that the aod-2 and aod-5 genes of Neurospora crassa encode transcription factors of the zinc-cluster family. Electrophoretic mobility shift assays show that the DNA-binding domains of the AOD2 and AOD5 proteins act in tandem to bind a sequence element in the alternative oxidase gene promoter that is required for expression. Both proteins contain potential PAS domains near their C terminus, which are found primarily in proteins involved in signal transduction.
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514
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Xing S, Zachgo S. ROXY1 and ROXY2, two Arabidopsis glutaredoxin genes, are required for anther development. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2008; 53:790-801. [PMID: 18036205 DOI: 10.1111/j.1365-313x.2007.03375.x] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Glutaredoxins (GRXs) are small oxidoreductases that are involved in various cellular processes and play a crucial role in responses to oxidative stress. Three GRX subgroups exist in plants, and GRXs with active sites of the CPYC and CGFS types are common to pro- and eukaryotes. In contrast, GRXs with the CC type motif have so far only been identified in land plants. Here, we report that the two CC-type GRXs ROXY1 and ROXY2 together control anther development in Arabidopsis thaliana. Single roxy1 and roxy2 mutants are fertile and produce normal anthers. However, roxy1 roxy2 double mutants are sterile and do not produce pollen. Strikingly, abaxial and adaxial anther lobe differentiation are differently affected, with early lobe differentiation being defective in the adaxial lobes, whereas later steps during pollen mother cell differentiation are disrupted in the abaxial lobes. Expression studies show that ROXY1 and ROXY2 are expressed with overlapping patterns during anther development. Lack of ROXY1 and ROXY2 function affects a large number of anther genes at the transcriptional level. Genetic and RT-PCR data imply that ROXY1/2 function downstream of the early-acting anther gene SPOROCYTELESS/NOZZLE and upstream of DYSFUNCTIONAL TAPETUM1, controlling tapetum development. Mutagenesis of a conserved glutathione-binding glycine in the ROXY1 protein indicates that CC-type GRXs need to interact with glutathione to catalyze essential biosynthetic reactions. Analysis of these two novel anther genes indicates that redox regulation, as well as participating in plant stress defense mechanisms, might play a major role in the control of male gametogenesis.
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Affiliation(s)
- Shuping Xing
- Max Planck Institute for Plant Breeding Research, 50829 Cologne, Germany
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515
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El-Maarouf-Bouteau H, Bailly C. Oxidative signaling in seed germination and dormancy. PLANT SIGNALING & BEHAVIOR 2008; 3:175-82. [PMID: 19513212 PMCID: PMC2634111 DOI: 10.4161/psb.3.3.5539] [Citation(s) in RCA: 181] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2008] [Accepted: 01/08/2008] [Indexed: 05/18/2023]
Abstract
Reactive Oxygen Species (ROS) play a key role in various events of seed life. In orthodox seeds, ROS are produced from embryogenesis to germination, i.e., in metabolically active cells, but also in quiescent dry tissues during after ripening and storage, owing various mechanisms depending on the seed moisture content. Although ROS have been up to now widely considered as detrimental to seeds, recent advances in plant physiology signaling pathways has lead to reconsider their role. ROS accumulation can therefore be also beneficial for seed germination and seedling growth by regulating cellular growth, ensuring a protection against pathogens or controlling the cell redox status. ROS probably also act as a positive signal in seed dormancy release. They interact with abscisic acid and gibberellins transduction pathway and are likely to control numerous transcription factors and properties of specific protein through their carbonylation.
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516
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Berndt C, Lillig CH, Holmgren A. Thioredoxins and glutaredoxins as facilitators of protein folding. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1783:641-50. [PMID: 18331844 DOI: 10.1016/j.bbamcr.2008.02.003] [Citation(s) in RCA: 188] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2008] [Revised: 02/05/2008] [Accepted: 02/06/2008] [Indexed: 12/27/2022]
Abstract
Thiol-disulfide oxidoreductase systems of bacterial cytoplasm and eukaryotic cytosol favor reducing conditions and protein thiol groups, while bacterial periplasm and eukaryotic endoplasmatic reticulum provide oxidizing conditions and a machinery for disulfide bond formation in the secretory pathway. Oxidoreductases of the thioredoxin fold superfamily catalyze steps in oxidative protein folding via protein-protein interactions and covalent catalysis to act as chaperones and isomerases of disulfides to generate a native fold. The active site dithiol/disulfide of thioredoxin fold proteins is CXXC where variations of the residues inside the disulfide ring are known to increase the redox potential like in protein disulfide isomerases. In the catalytic mechanism thioredoxin fold proteins bind to target proteins through conserved backbone-backbone hydrogen bonds and induce conformational changes of the target disulfide followed by nucleophilic attack by the N-terminally located low pK(a) Cys residue. This generates a mixed disulfide covalent bond which subsequently is resolved by attack from the C-terminally located Cys residue. This review will focus on two members of the thioredoxin superfamily of proteins known to be crucial for maintaining a reduced intracellular redox state, thioredoxin and glutaredoxin, and their potential functions as facilitators and regulators of protein folding and chaperone activity.
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Affiliation(s)
- Carsten Berndt
- The Medical Nobel Institute for Biochemistry, Karolinska Institutet, Stockholm, Sweden
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517
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Gupta D, Crosby ME, Almasan A, Macklis RM. Regulation of CD20 expression by radiation-induced changes in intracellular redox status. Free Radic Biol Med 2008; 44:614-23. [PMID: 18060882 PMCID: PMC2917596 DOI: 10.1016/j.freeradbiomed.2007.10.048] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2007] [Revised: 10/12/2007] [Accepted: 10/17/2007] [Indexed: 11/15/2022]
Abstract
Increasing the levels of CD20 expression in cells that harbor low CD20 levels may enhance their responsiveness to CD20-specific antibody therapies. Here, we examined the regulation of CD20 expression after treatment with 0.5-2.0 Gy X-irradiation and hydrogen peroxide (H(2)O(2)), in the presence or absence of known antioxidants, in the Burkitt lymphoma cell lines Daudi and Raji. Irradiation of cells enhanced cell-surface CD20 expression; the kinetics and extent of this change were cell-type specific and time-dependent. The kinetics of reactive oxygen species generation and changes in mitochondrial membrane potential after irradiation were also correlated with changes in CD20 expression. Raji and Daudi cells treated with H(2)O(2) showed a 2-to 2.5-fold increase in CD20 expression at 12 and 20 h, respectively. Buthionine sulfoximine, which depletes glutathione, also increased surface CD20, whereas antioxidants, such as PEG-catalase, PEG-SOD, vitamin C, and amifostine, decreased CD20 expression induced by radiation or H(2)O(2). The antioxidant-mediated decrease in CD20 expression induced by radiation or H(2)O(2) suggests a mechanism involving redox regulation. These results demonstrate the critical role of radiation-induced oxidative stress in CD20 expression and may have implications for defining and improving the efficacy of CD20-targeted antibody therapy and radioimmunotherapy.
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Affiliation(s)
- Damodar Gupta
- Department of Radiation Oncology, Taussig Cancer Center, Cleveland Clinic, Cleveland, OH 44195, USA
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Meredith E. Crosby
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA
- Department of Environmental Health Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Alexandru Almasan
- Department of Radiation Oncology, Taussig Cancer Center, Cleveland Clinic, Cleveland, OH 44195, USA
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Roger M. Macklis
- Department of Radiation Oncology, Taussig Cancer Center, Cleveland Clinic, Cleveland, OH 44195, USA
- Corresponding author. Fax: +1 216 445 7595. (R.M. Macklis)
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518
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Shahpiri A, Svensson B, Finnie C. The NADPH-dependent thioredoxin reductase/thioredoxin system in germinating barley seeds: gene expression, protein profiles, and interactions between isoforms of thioredoxin h and thioredoxin reductase. PLANT PHYSIOLOGY 2008; 146:789-99. [PMID: 18162587 PMCID: PMC2245843 DOI: 10.1104/pp.107.113639] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2007] [Accepted: 12/12/2007] [Indexed: 05/25/2023]
Abstract
The NADPH-dependent thioredoxin reductase (NTR)/thioredoxin (Trx) system catalyzes disulfide bond reduction in the cytoplasm and mitochondrion. Trx h is suggested to play an important role in seed development, germination, and seedling growth. Plants have multiple isoforms of Trx h and NTR; however, little is known about the roles of the individual isoforms. Trx h isoforms from barley (Hordeum vulgare) seeds (HvTrxh1 and HvTrxh2) were characterized previously. In this study, two NTR isoforms (HvNTR1 and HvNTR2) were identified, enabling comparison of gene expression, protein appearance, and interaction between individual NTR and Trx h isoforms in barley embryo and aleurone layers. Although mRNA encoding both Trx h isoforms is present in embryo and aleurone layers, the corresponding proteins differed in spatiotemporal appearance. HvNTR2, but not HvNTR1, gene expression seems to be regulated by gibberellic acid. Recombinant HvNTR1 and HvNTR2 exhibited virtually the same affinity toward HvTrxh1 and HvTrxh2, whereas HvNTR2 has slightly higher catalytic activity than HvNTR1 with both Trx h isoforms, and HvNTR1 has slightly higher catalytic activity toward HvTrxh1 than HvTrxh2. Notably, both NTRs reduced Trx h at the acidic conditions residing in the starchy endosperm during germination. Interspecies reactions between the barley proteins and Escherichia coli Trx or Arabidopsis thaliana NTR, respectively, occurred with 20- to 90-fold weaker affinity. This first investigation of regulation and interactions between members of the NTR/Trx system in barley seed tissues suggests that different isoforms are differentially regulated but may have overlapping roles, with HvNTR2 and HvTrxh1 being the predominant isoforms in the aleurone layer.
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Affiliation(s)
- Azar Shahpiri
- Enzyme and Protein Chemistry, BioCentrum-DTU, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
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519
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Wen F, Xing D, Zhang L. Hydrogen peroxide is involved in high blue light-induced chloroplast avoidance movements in Arabidopsis. JOURNAL OF EXPERIMENTAL BOTANY 2008; 59:2891-901. [PMID: 18550599 DOI: 10.1093/jxb/ern147] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
One of the most important functions of blue light (BL) is to induce chloroplast movements in order to reduce the damage to the photosynthetic machinery under excess light. Hydrogen peroxide (H(2)O(2)), which is commonly generated under various environmental stimuli, can act as a signalling molecule that regulates a number of developmental processes and stress responses. To investigate whether H(2)O(2) is involved in high-fluence BL-induced chloroplast avoidance movements, a laser scanning confocal microscope and a luminescence spectrometer were used to observe H(2)O(2) generation in situ with the assistance of the fluorescence probe dichlorofluorescein diacetate (H(2)DCF-DA). After treatment with high-fluence BL, an enhanced accumulation of H(2)O(2), indicated by the fluorescence intensity of DCF, can be observed in leaf cells of Arabidopsis thaliana. Exogenously applied H(2)O(2) promotes the high-fluence BL-induced chloroplast movements in a concentration-dependent manner within the range of 0-10(-4) M, not only increasing the degree of movements but also accelerating the start of migrations. Moreover, the high-fluence BL-induced H(2)O(2) generation and the subsequent chloroplast movements can be largely abolished by the administration of the H(2)O(2)-specific scavenger catalase and other antioxidants. In addition, in-depth subcellular experiments indicated that high-fluence BL-induced H(2)O(2) generation can be partly abolished by the addition of diphenyleneiodonium (DPI), which is an NADPH oxidase inhibitor, and the blocker of electron transport chain dichlorophenyl dimethylurea (DCMU), respectively. The results presented here suggest that high-fluence BL can induce H(2)O(2) generation at both the plasma membrane and the chloroplast, and that the production of H(2)O(2) is involved in high-fluence BL-induced chloroplast avoidance movements.
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Affiliation(s)
- Feng Wen
- MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, South China Normal University, Guangzhou 510631, China
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520
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Meyer AJ, Fricker MD. Imaging Thiol-Based Redox Processes in Live Cells. SULFUR METABOLISM IN PHOTOTROPHIC ORGANISMS 2008. [DOI: 10.1007/978-1-4020-6863-8_24] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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521
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Chutkow WA, Patwari P, Yoshioka J, Lee RT. Thioredoxin-interacting Protein (Txnip) Is a Critical Regulator of Hepatic Glucose Production. J Biol Chem 2008; 283:2397-406. [DOI: 10.1074/jbc.m708169200] [Citation(s) in RCA: 147] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
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522
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Shibagaki N, Grossman A. The State of Sulfur Metabolism in Algae: From Ecology to Genomics. SULFUR METABOLISM IN PHOTOTROPHIC ORGANISMS 2008. [DOI: 10.1007/978-1-4020-6863-8_13] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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523
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Dietzel L, Steiner S, Schröter Y, Pfannschmidt* T. Retrograde Signalling. PLANT CELL MONOGRAPHS 2008. [DOI: 10.1007/7089_2008_41] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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524
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Rouhier N, Lemaire SD, Jacquot JP. The role of glutathione in photosynthetic organisms: emerging functions for glutaredoxins and glutathionylation. ANNUAL REVIEW OF PLANT BIOLOGY 2008; 59:143-66. [PMID: 18444899 DOI: 10.1146/annurev.arplant.59.032607.092811] [Citation(s) in RCA: 334] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Glutathione, a tripeptide with the sequence gamma-Glu-Cys-Gly, exists either in a reduced form with a free thiol group or in an oxidized form with a disulfide between two identical molecules. We describe here briefly the pathways involved in the synthesis, reduction, polymerization, and degradation of glutathione, as well as its distribution throughout the plant and its redox buffering capacities. The function of glutathione in xenobiotic and heavy metal detoxification, plant development, and plant-pathogen interactions is also briefly discussed. Several lines of evidence indicate that glutathione and glutaredoxins (GRXs) are implicated in the response to oxidative stress through the regeneration of enzymes involved in peroxide and methionine sulfoxide reduction. Finally, emerging functions for plant GRXs and glutathione concern the regulation of protein activity via glutathionylation and the capacity of some GRXs to bind iron sulfur centers and for some of them to transfer FeS clusters into apoproteins.
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Affiliation(s)
- Nicolas Rouhier
- Unité Mixte de Recherches, 1136 INRA-UHP Interaction Arbres-Microorganismes, IFR 110 GEEF, Nancy University, Faculté des Sciences, 54506 Vandoeuvre Cedex, France.
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525
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Meyer AJ, Brach T, Marty L, Kreye S, Rouhier N, Jacquot JP, Hell R. Redox-sensitive GFP in Arabidopsis thaliana is a quantitative biosensor for the redox potential of the cellular glutathione redox buffer. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2007; 52:973-86. [PMID: 17892447 DOI: 10.1111/j.1365-313x.2007.03280.x] [Citation(s) in RCA: 336] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The cellular glutathione redox buffer is assumed to be part of signal transduction pathways transmitting environmental signals during biotic and abiotic stress, and thus is essential for regulation of metabolism and development. Ratiometric redox-sensitive GFP (roGFP) expressed in Arabidopsis thaliana reversibly responds to redox changes induced by incubation with H(2)O(2) or DTT. Kinetic analysis of these redox changes, combined with detailed characterization of roGFP2 in vitro, shows that roGFP2 expressed in the cytosol senses the redox potential of the cellular glutathione buffer via glutaredoxin (GRX) as a mediator of reversible electron flow between glutathione and roGFP2. The sensitivity of roGFP2 toward the glutathione redox potential was tested in vivo through manipulating the glutathione (GSH) content of wild-type plants, through expression of roGFP2 in the cytosol of low-GSH mutants and the endoplasmic reticulum (ER) of wild-type plants, as well as through wounding as an example for stress-induced redox changes. Provided the GSH concentration is known, roGFP2 facilitates the determination of the degree of oxidation of the GSH solution. Assuming sufficient glutathione reductase activity and non-limiting NADPH supply, the observed almost full reduction of roGFP2 in vivo suggests that a 2.5 mm cytosolic glutathione buffer would contain only 25 nm oxidized glutathione disulfide (GSSG). The high sensitivity of roGFP2 toward GSSG via GRX enables the use of roGFP2 for monitoring stress-induced redox changes in vivo in real time. The results with roGFP2 as an artificial GRX target further suggest that redox-triggered changes of biologic processes might be linked directly to the glutathione redox potential via GRX as the mediator.
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Affiliation(s)
- Andreas J Meyer
- Heidelberg Institute of Plant Sciences, University of Heidelberg, 69120 Heidelberg, Germany.
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526
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Vitamin B1 biosynthesis in plants requires the essential iron sulfur cluster protein, THIC. Proc Natl Acad Sci U S A 2007; 104:19637-42. [PMID: 18048325 DOI: 10.1073/pnas.0709597104] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Vitamin B1 (thiamin) is an essential compound in all organisms acting as a cofactor in key metabolic reactions and has furthermore been implicated in responses to DNA damage and pathogen attack in plants. Despite the fact that it was discovered almost a century ago and deficiency is a widespread health problem, much remains to be deciphered about its biosynthesis. The vitamin is composed of a thiazole and pyrimidine heterocycle, which can be synthesized by prokaryotes, fungi, and plants. Plants are the major source of the vitamin in the human diet, yet little is known about the biosynthesis of the compound therein. In particular, it has never been verified whether the pyrimidine heterocycle is derived from purine biosynthesis through the action of the THIC protein as in bacteria, rather than vitamin B6 and histidine as demonstrated for fungi. Here, we identify a homolog of THIC in Arabidopsis and demonstrate its essentiality not only for vitamin B1 biosynthesis, but also plant viability. This step takes place in the chloroplast and appears to be regulated at several levels, including through the presence of a riboswitch in the 3'-untranslated region of THIC. Strong evidence is provided for the involvement of an iron-sulfur cluster in the remarkable chemical rearrangement reaction catalyzed by the THIC protein for which there is no chemical precedent. The results suggest that vitamin B1 biosynthesis in plants is in fact more similar to prokaryotic counterparts and that the THIC protein is likely to be the key regulatory protein in the pathway.
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527
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Mata-Cabana A, Florencio FJ, Lindahl M. Membrane proteins from the cyanobacteriumSynechocystis sp. PCC 6803 interacting with thioredoxin. Proteomics 2007; 7:3953-63. [DOI: 10.1002/pmic.200700410] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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528
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Okegawa Y, Long TA, Iwano M, Takayama S, Kobayashi Y, Covert SF, Shikanai T. A balanced PGR5 level is required for chloroplast development and optimum operation of cyclic electron transport around photosystem I. PLANT & CELL PHYSIOLOGY 2007; 48:1462-71. [PMID: 17913767 DOI: 10.1093/pcp/pcm116] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
PSI cyclic electron transport contributes markedly to photosynthesis and photoprotection in flowering plants. Although the thylakoid protein PGR5 (Proton Gradient Regulation 5) has been shown to be essential for the main route of PSI cyclic electron transport, its exact function remains unclear. In transgenic Arabidopsis plants overaccumulating PGR5 in the thylakoid membrane, chloroplast development was delayed, especially in the cotyledons. Although photosynthetic electron transport was not affected during steady-state photosynthesis, a high level of non-photochemical quenching (NPQ) was transiently induced after a shift of light conditions. This phenotype was explained by elevated activity of PSI cyclic electron transport, which was monitored in an in vitro system using ruptured chloroplasts, and also in leaves. The effect of overaccumulation of PGR5 was specific to the antimycin A-sensitive pathway of PSI cyclic electron transport but not to the NAD(P)H dehydrogenase (NDH) pathway. We propose that a balanced PGR5 level is required for efficient regulation of the rate of antimycin A-sensitive PSI cyclic electron transport, although the rate of PSI cyclic electron transport is probably also regulated by other factors during steady-state photosynthesis.
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Affiliation(s)
- Yuki Okegawa
- Graduate School of Agriculture, Kyushu University, 6-10-1 Hakozaki, Higashiku, Fukuoka, 812-8581 Japan
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529
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Jones AM, Lindow SE, Wildermuth MC. Salicylic acid, yersiniabactin, and pyoverdin production by the model phytopathogen Pseudomonas syringae pv. tomato DC3000: synthesis, regulation, and impact on tomato and Arabidopsis host plants. J Bacteriol 2007; 189:6773-86. [PMID: 17660289 PMCID: PMC2045226 DOI: 10.1128/jb.00827-07] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2007] [Accepted: 07/16/2007] [Indexed: 01/07/2023] Open
Abstract
A genetically tractable model plant pathosystem, Pseudomonas syringae pv. tomato DC3000 on tomato and Arabidopsis thaliana hosts, was used to investigate the role of salicylic acid (SA) and iron acquisition via siderophores in bacterial virulence. Pathogen-induced SA accumulation mediates defense in these plants, and DC3000 contains the genes required for the synthesis of SA, the SA-incorporated siderophore yersiniabactin (Ybt), and the fluorescent siderophore pyoverdin (Pvd). We found that DC3000 synthesizes SA, Ybt, and Pvd under iron-limiting conditions in culture. Synthesis of SA and Ybt by DC3000 requires pchA, an isochorismate synthase gene in the Ybt genomic cluster, and exogenous SA can restore Ybt production by the pchA mutant. Ybt was also produced by DC3000 in planta, suggesting that Ybt plays a role in DC3000 pathogenesis. However, the pchA mutant did not exhibit any growth defect or altered virulence in plants. This lack of phenotype was not attributable to plant-produced SA restoring Ybt production, as the pchA mutant grew similarly to DC3000 in an Arabidopsis SA biosynthetic mutant, and in planta Ybt was not detected in pchA-infected wild-type plants. In culture, no growth defect was observed for the pchA mutant versus DC3000 for any condition tested. Instead, enhanced growth of the pchA mutant was observed under stringent iron limitation and additional stresses. This suggests that SA and Ybt production by DC3000 is costly and that Pvd is sufficient for iron acquisition. Further exploration of the comparative synthesis and utility of Ybt versus Pvd production by DC3000 found siderophore-dependent amplification of ybt gene expression to be absent, suggesting that Ybt may play a yet unknown role in DC3000 pathogenesis.
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Affiliation(s)
- Alexander M Jones
- Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, CA 94720-3102, USA
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530
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Traverso JA, Vignols F, Chueca A. Thioredoxin and Redox Control within the New Concept of Oxidative Signaling. PLANT SIGNALING & BEHAVIOR 2007; 2:426-7. [PMID: 19704622 PMCID: PMC2634235 DOI: 10.4161/psb.2.5.4419] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2007] [Accepted: 05/10/2007] [Indexed: 05/21/2023]
Abstract
During the last decade, plant thioredoxins (TRX) h-type have been shown to be implicated in several new roles like the protection against the oxidative stress by their ability to reduce some antioxidant proteins as peroxiredoxins (PRX) or methionine-sulphoxide-reductases (MSR). However, the concept of the oxidative stress is changing and this fact raises the question of the TRX roles in this new context. In the January issue of Plant Physiology, we have presented two TRXsh from Pisum sativum differently involved in the control of the redox status. PsTRXh1 is an h-type TRX that acts by reducing classical antioxidant proteins. PsTRXh2 seems to be also involved in redox control, however it could act contrary to its counterpart h1. Both proteins may play antagonistic roles in pea in order to lead a better control of the redox status.
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Affiliation(s)
- Jose A Traverso
- Departamento de Bioquimica; Biologia Celular y Molecular de Plantas; Estacion Experimental del Zaidin; Granada, Spain
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531
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Castro-Sowinski S, Matan O, Bonafede P, Okon Y. A thioredoxin of Sinorhizobium meliloti CE52G is required for melanin production and symbiotic nitrogen fixation. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2007; 20:986-93. [PMID: 17724847 DOI: 10.1094/mpmi-20-8-0986] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
A miniTn5-induced mutant of a melanin-producing strain of Sinorhizobium meliloti (CE52G) that does not produce melanin was mapped to a gene identified as a probable thioredoxin gene. It was proved that the thiol-reducing activity of the mutant was affected. Addition to the growth medium of substrates that induce the production of melanin (L-tyrosine, guaiacol, orcinol) increased the thioredoxin-like (trxL) mRNA level in the wild-type strain. The mutant strain was affected in the response to paraquat-induced oxidative stress, symbiotic nitrogen fixation, and both laccase and tyrosinase activities. The importance of thioredoxin in melanin production in bacteria, through the regulation of laccase or tyrosinase activities, or both, by the redox state of structural or catalytic SH groups, is discussed.
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Affiliation(s)
- Susana Castro-Sowinski
- Department of Plant Pathology and Microbiology, The Otto Warburg Minerva Center for Agricultural Biotechnology, The Hebrew University of Jerusalem, Faculty of Agricultural, Food and Environmental Quality Sciences, Rehovot, Israel.
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532
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Pukacka S, Ratajczak E. Ascorbate and glutathione metabolism during development and desiccation of orthodox and recalcitrant seeds of the genus Acer. FUNCTIONAL PLANT BIOLOGY : FPB 2007; 34:601-613. [PMID: 32689388 DOI: 10.1071/fp07013] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2007] [Accepted: 04/04/2007] [Indexed: 05/27/2023]
Abstract
The ascorbate-glutathione system was studied during development and desiccation of seeds of two Acer species differing in desiccation tolerance: Norway maple (Acer platanoides L., orthodox) and sycamore (Acer pseudoplatanus L., recalcitrant). The results showed remarkable differences in the concentration and redox balance of ascorbate and glutathione between these two kinds of seeds during development, and a significant dependence between glutathione content and acquisition of desiccation tolerance in Norway maple seeds. There were relatively small differences between the species in the activities of enzymes of the ascorbate-glutathione cycle: ascorbate peroxidase (APX, EC 1.11.1.11), monodehydroascorbate reductase (MR, EC 1.6.5.4), dehydroascorbate reductase (DHAR, EC 1.8.5.1), and glutathione reductase (GR, EC 1.6.4.2). At the end of seed maturation, ascorbic acid content and the activities of the above enzymes was about the same in both species The electrophoretic pattern of APX isoenzymes was also similar for both species, and the intensity of the bands decreased at the end of seed maturation in both species. When sycamore seeds were desiccated to a moisture content of less than 26%, there was a marked decrease in seed viability and an increase in the production of reactive oxygen species. During desiccation, Norway maple seeds had a more active defence system, which was reflected in a higher glutathione content, a higher glutathione redox status, a higher ascorbate redox status, and higher activities of APX, MR, DHAR, GR and GPX (glutathione peroxidase). During desiccation, sulfhydryl-to-disulfide transition into proteins was more intense in Norway maple seeds than sycamore seeds. All of these results suggest that, in orthodox seeds, the ascorbate-glutathione cycle plays an important role in the acquisition of tolerance to desiccation, in protein maturation, and in protection from reactive oxygen species.
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Affiliation(s)
- Stanislawa Pukacka
- Seed Biochemistry Laboratory, Institute of Dendrology, Polish Academy of Sciences, 62-035 Kórnik, Poland
| | - Ewelina Ratajczak
- Seed Biochemistry Laboratory, Institute of Dendrology, Polish Academy of Sciences, 62-035 Kórnik, Poland
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533
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Müller J, Naguleswaran A, Müller N, Hemphill A. Neospora caninum: functional inhibition of protein disulfide isomerase by the broad-spectrum anti-parasitic drug nitazoxanide and other thiazolides. Exp Parasitol 2007; 118:80-8. [PMID: 17720161 DOI: 10.1016/j.exppara.2007.06.008] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2007] [Revised: 06/18/2007] [Accepted: 06/25/2007] [Indexed: 11/23/2022]
Abstract
Nitazoxanide (NTZ) and several NTZ-derivatives (thiazolides) have been shown to exhibit considerable anti-Neospora caninum tachyzoite activity in vitro. We coupled tizoxanide (TIZ), the deacetylated metabolite, to epoxy-agarose-resin and performed affinity chromatography with N. caninum tachyzoite extracts. Two main protein bands of 52 and 43kDa were isolated. The 52kDa protein was readily recognized by antibodies directed against NcPDI, and mass spectrometry confirmed its identity. Poly-histidine-tagged NcPDI-cDNA was expressed in Escherichia coli and recombinant NcPDI (recNcPDI) was purified by Co2+-affinity chromatography. By applying an enzyme assay based on the measurement of insulin crosslinking activity, recNcPDI exhibited properties reminiscent for PDIs, and its activity was impaired upon the addition of classical PDI inhibitors such as bacitracin (1-2mM), para-chloromercuribenzoic acid (0.1-1mM) and tocinoic acid (0.1-1mM). RecNcPDI-mediated insulin crosslinking was inhibited by NTZ (5-100 microM) in a dose-dependent manner. In addition, the enzymatic activity of recNcPDI was inhibited by those thiazolides that also affected parasite proliferation. Thus, thiazolides readily interfere with NcPDI, and possibly also with PDIs from other microorganisms susceptible to thiazolides.
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Affiliation(s)
- Joachim Müller
- Institute of Parasitology, University of Berne, Länggass-Strasse 122, CH-3012 Berne, Switzerland.
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534
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Alkhalfioui F, Renard M, Vensel WH, Wong J, Tanaka CK, Hurkman WJ, Buchanan BB, Montrichard F. Thioredoxin-linked proteins are reduced during germination of Medicago truncatula seeds. PLANT PHYSIOLOGY 2007; 144:1559-79. [PMID: 17513483 PMCID: PMC1914137 DOI: 10.1104/pp.107.098103] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Germination of cereals is accompanied by extensive change in the redox state of seed proteins. Proteins present in oxidized form in dry seeds are converted to the reduced state following imbibition. Thioredoxin (Trx) appears to play a role in this transition in cereals. It is not known, however, whether Trx-linked redox changes are restricted to cereals or whether they take place more broadly in germinating seeds. To gain information on this point, we have investigated a model legume, Medicago truncatula. Two complementary gel-based proteomic approaches were followed to identify Trx targets in seeds: Proteins were (1) labeled with a thiol-specific probe, monobromobimane (mBBr), following in vitro reduction by an NADP/Trx system, or (2) isolated on a mutant Trx affinity column. Altogether, 111 Trx-linked proteins were identified with few differences between axes and cotyledons. Fifty nine were new, 34 found previously in cereal or peanut seeds, and 18 in other plants or photosynthetic organisms. In parallel, the redox state of proteins assessed in germinating seeds using mBBr revealed that a substantial number of proteins that are oxidized or partly reduced in dry seeds became more reduced upon germination. The patterns were similar for proteins reduced in vivo during germination or in vitro by Trx. In contrast, glutathione and glutaredoxin were less effective as reductants in vitro. Overall, more than half of the potential targets identified with the mBBr labeling procedure were reduced during germination. The results provide evidence that Trx functions in the germination of seeds of dicotyledons as well as monocotyledons.
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Affiliation(s)
- Fatima Alkhalfioui
- Physiologie Moléculaire des Semences, Unité Mixte de Recherche 1191, Université d'Angers, Institut National d'Horticulture, Institut National de la Recherche Agronomique, Anjou Recherche Semences, Angers Cedex 01, France
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535
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Dai S, Friemann R, Glauser DA, Bourquin F, Manieri W, Schürmann P, Eklund H. Structural snapshots along the reaction pathway of ferredoxin–thioredoxin reductase. Nature 2007; 448:92-6. [PMID: 17611542 DOI: 10.1038/nature05937] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2007] [Accepted: 05/17/2007] [Indexed: 11/08/2022]
Abstract
Oxygen-evolving photosynthetic organisms regulate carbon metabolism through a light-dependent redox signalling pathway. Electrons are shuttled from photosystem I by means of ferredoxin (Fdx) to ferredoxin-thioredoxin reductase (FTR), which catalyses the two-electron-reduction of chloroplast thioredoxins (Trxs). These modify target enzyme activities by reduction, regulating carbon flow. FTR is unique in its use of a [4Fe-4S] cluster and a proximal disulphide bridge in the conversion of a light signal into a thiol signal. We determined the structures of FTR in both its one- and its two-electron-reduced intermediate states and of four complexes in the pathway, including the ternary Fdx-FTR-Trx complex. Here we show that, in the first complex (Fdx-FTR) of the pathway, the Fdx [2Fe-2S] cluster is positioned suitably for electron transfer to the FTR [4Fe-4S] centre. After the transfer of one electron, an intermediate is formed in which one sulphur atom of the FTR active site is free to attack a disulphide bridge in Trx and the other sulphur atom forms a fifth ligand for an iron atom in the FTR [4Fe-4S] centre--a unique structure in biology. Fdx then delivers a second electron that cleaves the FTR-Trx heterodisulphide bond, which occurs in the Fdx-FTR-Trx complex. In this structure, the redox centres of the three proteins are aligned to maximize the efficiency of electron transfer from the Fdx [2Fe-2S] cluster to the active-site disulphide of Trxs. These results provide a structural framework for understanding the mechanism of disulphide reduction by an iron-sulphur enzyme and describe previously unknown interaction networks for both Fdx and Trx (refs 4-6).
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Affiliation(s)
- Shaodong Dai
- Howard Hughes Medical Institute, Integrated Department of Immunology, National Jewish Medical and Research Center & University of Colorado Health Sciences Center, 1400 Jackson Street, Denver, Colorado 80206, USA.
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536
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Fermani S, Sparla F, Falini G, Martelli PL, Casadio R, Pupillo P, Ripamonti A, Trost P. Molecular mechanism of thioredoxin regulation in photosynthetic A2B2-glyceraldehyde-3-phosphate dehydrogenase. Proc Natl Acad Sci U S A 2007; 104:11109-14. [PMID: 17573533 PMCID: PMC1904167 DOI: 10.1073/pnas.0611636104] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Chloroplast glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a light-regulated, NAD(P)H-dependent enzyme involved in plant photosynthetic carbon reduction. Unlike lower photosynthetic organisms, which only contain A(4)-GAPDH, the major GAPDH isoform of land plants is made up of A and B subunits, the latter containing a C-terminal extension (CTE) with fundamental regulatory functions. Light-activation of AB-GAPDH depends on the redox state of a pair of cysteines of the CTE, which can form a disulfide bond under control of thioredoxin f, leading to specific inhibition of the NADPH-dependent activity. The tridimensional structure of A(2)B(2)-GAPDH from spinach chloroplasts, crystallized in the oxidized state, shows that each disulfide-containing CTE is docked into a deep cleft between a pair of A and B subunits. The structure of the CTE was derived from crystallographic data and computational modeling and confirmed by site-specific mutagenesis. Structural analysis of oxidized A(2)B(2)-GAPDH and chimeric mutant [A+CTE](4)-GAPDH revealed that Arg-77, which is essential for coenzyme specificity and high NADPH-dependent activity, fails to interact with NADP in these kinetically inhibited GAPDH tetramers and is attracted instead by negative residues of oxidized CTE. Other subtle changes in catalytic domains and overall conformation of the tetramers were noticed in oxidized A(2)B(2)-GAPDH and [A+CTE](4)-GAPDH, compared with fully active A(4)-GAPDH. The CTE is envisioned as a redox-sensitive regulatory domain that can force AB-GAPDH into a kinetically inhibited conformation under oxidizing conditions, which also occur during dark inactivation of the enzyme in vivo.
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Affiliation(s)
- S. Fermani
- *Department of Chemistry, University of Bologna, Via Selmi 2, 40126 Bologna, Italy; and
| | - F. Sparla
- Laboratory of Molecular Plant Physiology and
| | - G. Falini
- *Department of Chemistry, University of Bologna, Via Selmi 2, 40126 Bologna, Italy; and
| | - P. L. Martelli
- Biocomputing Group, Department of Experimental Evolutionary Biology, University of Bologna, Via Irnerio 42, 40126 Bologna, Italy
| | - R. Casadio
- Biocomputing Group, Department of Experimental Evolutionary Biology, University of Bologna, Via Irnerio 42, 40126 Bologna, Italy
| | - P. Pupillo
- Laboratory of Molecular Plant Physiology and
| | - A. Ripamonti
- *Department of Chemistry, University of Bologna, Via Selmi 2, 40126 Bologna, Italy; and
| | - P. Trost
- Laboratory of Molecular Plant Physiology and
- To whom correspondence should be addressed. E-mail:
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537
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Müller J, Sterk M, Hemphill A, Müller N. Characterization of Giardia lamblia WB C6 clones resistant to nitazoxanide and to metronidazole. J Antimicrob Chemother 2007; 60:280-7. [PMID: 17561498 DOI: 10.1093/jac/dkm205] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
OBJECTIVES The characterization of Giardia lamblia WB C6 strains resistant to metronidazole and to the nitro-thiazole nitazoxanide [2-acetolyloxy-N-(5-nitro 2-thiazolyl) benzamide] as the parent compound of thiazolides, a novel class of anti-infective drugs with a broad spectrum of activities against a wide variety of helminths, protozoa and enteric bacteria. METHODS Issuing from G. lamblia WB C6, we have generated two strains exhibiting resistance to nitazoxanide (strain C4) and to metronidazole (strain C5) and determined their susceptibilities to both drugs. Using quantitative RT-PCR, we have analysed the expression of genes that are potentially involved in resistance formation, namely genes encoding pyruvate oxidoreductases (POR1 and POR2), nitroreductase (NR), protein disulphide isomerases (PDI2 and PDI4) and variant surface proteins (VSPs; TSA417). We have cloned and expressed PDI2 and PDI4 in Escherichia coli. Using an enzyme assay based on the polymerization of insulin, we have determined the activities of both enzymes in the presence and absence of nitazoxanide. RESULTS Whereas C4 was cross-resistant to nitazoxanide and to metronidazole, C5 was resistant only to metronidazole. Transcript levels of the potential targets for nitro-drugs POR1, POR2 and NR were only slightly modified, PDI2 transcript levels were increased in both resistant strains and PDI4 levels in C4. This correlated with the findings that the functional activities of recombinant PDI2 and PDI4 were inhibited by nitazoxanide. Moreover, drastic changes were observed in VSP gene expression. CONCLUSIONS These results suggest that resistance formation in Giardia against nitazoxanide and metronidazole is linked, and possibly mediated by, altered gene expression in drug-resistant strains compared with non-resistant strains of Giardia.
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Affiliation(s)
- Joachim Müller
- Institute of Parasitology, University of Berne, Länggass-Strasse 122, CH-3012 Berne, Switzerland.
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538
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Stitt M, Gibon Y, Lunn JE, Piques M. Multilevel genomics analysis of carbon signalling during low carbon availability: coordinating the supply and utilisation of carbon in a fluctuating environment. FUNCTIONAL PLANT BIOLOGY : FPB 2007; 34:526-549. [PMID: 32689382 DOI: 10.1071/fp06249] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2006] [Accepted: 12/06/2006] [Indexed: 06/11/2023]
Abstract
Plants alternate between a net surplus of carbon in the light and a net deficit at night. This is buffered by accumulating starch in the light and degrading it at night. Enough starch is accumulated to support degradation throughout the night, with a small amount remaining at the end of the 24-h diurnal cycle. This review discusses how this balance between the supply and utilisation of carbon is achieved in Arabidopsis. It is important to regulate starch turnover to avoid an acute carbon deficiency. A 2-4 h extension of the night leads to exhaustion of starch, a collapse of sugars, a switch from biosynthesis to catabolism and an acute inhibition of growth by low carbon, which is not immediately reversed when carbon becomes available again. In starchless pgm mutants, where sugars are depleted each night, this leads to a recurring inhibition of growth that is not reversed until 5-6 h into the following light period. Several lines of evidence show that starch accumulation is regulated in response to events that are initiated during periods of low carbon. Starch accumulation is decreased when small amounts of sucrose are included in the growth medium. Sets of sugar-responsive genes were identified by supplying sugars to carbon-starved seedlings, or by illuminating 5-week-old plants in the presence of 350 or 50 ppm [CO2]. Almost all of these genes show large diurnal changes in starchless pgm mutants, which are driven by the depletion of carbon during the night. Many show significant diurnal changes in wild type plants, showing that 'anticipatory' changes in signalling pathways occur before acute carbon limitation develops. However, these diurnal changes of transcripts do not lead to immediate changes of enzyme activities. Whereas an extension of the night leads to major changes of transcripts within 4-6 h, changes in enzyme activities require several days. In pgm, enzyme activities and the levels of >150 metabolites resemble those found in wild type plants after several days in the dark. It is concluded that diurnal changes in transcript levels are integrated, over days, as changes in the levels of enzymes. We hypothesise that this facilitates an adjustment of metabolism to a mid-term shift in the conditions, while ignoring noise due to diurnal changes and day-to-day fluctuations. The rapid adjustment of starch synthesis after a period of acute carbon depletion is a consequence of the transient inhibition of growth. This leads to accumulation of sugars when carbon becomes available again, which triggers a large increase in trehalose-6-phosphate. This signal metabolite promotes thioredoxin-dependent post-translational activation of ADP glucose pyrophosphorylase. Mid-term acclimation to a decreased carbon supply may be mediated by a combination of post-translational regulation, longer-term changes in enzyme activities, and a decrease in the rate of growth.
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Affiliation(s)
- Mark Stitt
- Max-Planck-Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14424 Golm, Germany
| | - Yves Gibon
- Max-Planck-Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14424 Golm, Germany
| | - John E Lunn
- Max-Planck-Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14424 Golm, Germany
| | - Maria Piques
- Max-Planck-Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14424 Golm, Germany
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539
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Ikegami A, Yoshimura N, Motohashi K, Takahashi S, Romano PGN, Hisabori T, Takamiya KI, Masuda T. The CHLI1 subunit of Arabidopsis thaliana magnesium chelatase is a target protein of the chloroplast thioredoxin. J Biol Chem 2007; 282:19282-91. [PMID: 17472958 DOI: 10.1074/jbc.m703324200] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Insertion of magnesium into protoporphyrin IX by magnesium chelatase is a key step in the chlorophyll biosynthetic pathway, which takes place in plant chloroplasts. ATP hydrolysis by the CHLI subunit of magnesium chelatase is an essential component of this reaction, and the activity of this enzyme is a primary determinant of the rate of magnesium insertion into the chlorophyll molecule (tetrapyrrole ring). Higher plant CHLI contains highly conserved cysteine residues and was recently identified as a candidate protein in a proteomic screen of thioredoxin target proteins (Balmer, Y., Koller, A., del Val, G., Manieri, W., Schurmann, P., and Buchanan, B. B. (2003) Proc. Natl. Acad. Sci. U. S. A. 100, 370-375). To study the thioredoxin-dependent regulation of magnesium chelatase, we first investigated the effect of thioredoxin on the ATPase activity of CHLI1, a major isoform of CHLI in Arabidopsis thaliana. The ATPase activity of recombinant CHLI1 was found to be fully inactivated by oxidation and easily recovered by thioredoxin-assisted reduction, suggesting that CHLI1 is a target protein of thioredoxin. Moreover, we identified one crucial disulfide bond located in the C-terminal helical domain of CHLI1 protein, which may regulate the binding of the nucleotide to the N-terminal catalytic domain. The redox state of CHLI was also found to alter in a light-dependent manner in vivo. Moreover, we successfully observed stimulation of the magnesium chelatase activity in isolated chloroplasts by reduction. Our findings strongly suggest that chlorophyll biosynthesis is subject to chloroplast biogenesis regulation networks to coordinate them with the photosynthetic pathways in chloroplasts.
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Affiliation(s)
- Akinori Ikegami
- Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta 4259, Yokohama 226-8501, Japan
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540
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Buchanan BB. Thioredoxin: an unexpected meeting place. PHOTOSYNTHESIS RESEARCH 2007; 92:145-8. [PMID: 17638116 DOI: 10.1007/s11120-007-9196-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Accepted: 05/13/2007] [Indexed: 05/16/2023]
Abstract
For much of the latter part of the 20th century, photosynthesis research at Berkeley was dominated by Daniel Arnon and Melvin Calvin. In this article, I have briefly described how their contributions jointly provided the foundation for our work on thioredoxin and how important Andrew Benson was to this effort.
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Affiliation(s)
- Bob B Buchanan
- Department of Plant and Microbial Biology, University of California, 111 Koshland Hall, Berkeley, CA 94720, USA.
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541
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Patwari P, Lee RT. Thioredoxins, mitochondria, and hypertension. THE AMERICAN JOURNAL OF PATHOLOGY 2007; 170:805-8. [PMID: 17322366 PMCID: PMC1864871 DOI: 10.2353/ajpath.2007.061243] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Endothelial dysfunction, often demonstrated by the loss of the endothelial cell's ability to cause vasodilation in response to appropriate stimuli, is one of the earliest events in the development of atherosclerosis. This has led to intense investigation of the factors affecting both the production and the degradation of NO, the endothelium-derived relaxing factor and a primary mediator of endothelial function. Reactive oxygen species (ROS), particularly superoxide anion, are well known to inhibit NO, and therefore the mechanisms by which endothelium regulates production of ROS are also of high interest. In this issue of The American Journal of Pathology, Zhang et al( 1) demonstrate regulation of such events by a mitochondria-specific thioredoxin, which reduces oxidative stress and increases NO bioavailability, thus preserving vascular endothelial cell function and preventing atherosclerosis development.
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Affiliation(s)
- Parth Patwari
- Partners Research Facility, 65 Landsdowne St., Rm. 280, Cambridge, MA 02139, USA
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542
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Trebst A. Inhibitors in the functional dissection of the photosynthetic electron transport system. PHOTOSYNTHESIS RESEARCH 2007; 92:217-24. [PMID: 17647089 DOI: 10.1007/s11120-007-9213-x] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2007] [Accepted: 06/08/2007] [Indexed: 05/09/2023]
Abstract
The significance of inhibitors and artificial electron acceptor and donor systems as experimental tools for studying the photosynthetic system is described by reviewing early classical articles. The historical development in unravelling the role and sequence of electron carriers and energy conserving sites in the electron transport chain is acknowledged. Emphasis is given to inhibitors of the acceptor side of photosystem II and of the plastoquinol oxidation site in the cytochrome b6/f complex. Their role in regulatory processes under redox control is introduced.
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Affiliation(s)
- Achim Trebst
- Plant Biochemistry, Ruhr-University, 44780 Bochum, Germany.
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543
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Müller J, Wastling J, Sanderson S, Müller N, Hemphill A. A novel Giardia lamblia nitroreductase, GlNR1, interacts with nitazoxanide and other thiazolides. Antimicrob Agents Chemother 2007; 51:1979-86. [PMID: 17438059 PMCID: PMC1891416 DOI: 10.1128/aac.01548-06] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The nitrothiazole analogue nitazoxanide [NTZ; 2-acetolyloxy-N-(5-nitro-2-thiazolyl)benzamide] represents the parent compound of a class of drugs referred to as thiazolides and exhibits a broad spectrum of activities against a wide variety of helminths, protozoa, and enteric bacteria infecting animals and humans. NTZ and other thiazolides are active against a wide range of other intracellular and extracellular protozoan parasites in vitro and in vivo, but their mode of action and respective subcellular target(s) have only recently been investigated. In order to identify potential targets of NTZ and other thiazolides in Giardia lamblia trophozoites, we have developed an affinity chromatography system using the deacetylated derivative of NTZ, tizoxanide (TIZ), as a ligand. Affinity chromatography on TIZ-agarose using cell extracts of G. lamblia trophozoites resulted in the isolation of an approximately 35-kDa polypeptide, which was identified by mass spectrometry as a nitroreductase (NR) homologue (EAA43030.1). NR was overexpressed as a six-histidine-tagged recombinant protein in Escherichia coli, purified, and then characterized using an assay for oxygen-insensitive NRs with dinitrotoluene as a substrate. This demonstrated that the NR was functionally active, and the protein was designated GlNR1. In this assay system, NR activity was severely inhibited by NTZ and other thiazolides, demonstrating that the antigiardial activity of these drugs could be, at least partially, mediated through inhibition of GlNR1.
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Affiliation(s)
- Joachim Müller
- Institute of Parasitology, University of Berne, Länggass-Strasse 122, CH-3012 Berne, Switzerland.
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544
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Lemaire SD, Michelet L, Zaffagnini M, Massot V, Issakidis-Bourguet E. Thioredoxins in chloroplasts. Curr Genet 2007; 51:343-65. [PMID: 17431629 DOI: 10.1007/s00294-007-0128-z] [Citation(s) in RCA: 157] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2007] [Revised: 03/05/2007] [Accepted: 03/09/2007] [Indexed: 01/03/2023]
Abstract
Thioredoxins (TRXs) are small disulfide oxidoreductases of ca. 12 kDa found in all free living organisms. In plants, two chloroplastic TRXs, named TRX f and TRX m, were originally identified as light dependent regulators of several carbon metabolism enzymes including Calvin cycle enzymes. The availability of genome sequences revealed an unsuspected multiplicity of TRXs in photosynthetic eukaryotes, including new chloroplastic TRX types. Moreover, proteomic approaches and focused studies allowed identification of 90 potential chloroplastic TRX targets. Lately, recent studies suggest the existence of a complex interplay between TRXs and other redox regulators such as glutaredoxins (GRXs) or glutathione. The latter is involved in a post-translational modification, named glutathionylation that could be controlled by GRXs. Glutathionylation appears to specifically affect the activity of TRX f and other chloroplastic enzymes and could thereby constitute a previously undescribed regulatory mechanism of photosynthetic metabolism under oxidative stress. After summarizing the initial studies on TRX f and TRX m, this review will focus on the most recent developments with special emphasis on the contributions of genomics and proteomics to the field of TRXs. Finally, new emerging interactions with other redox signaling pathways and perspectives for future studies will also be discussed.
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Affiliation(s)
- Stéphane D Lemaire
- Institut de Biotechnologie des Plantes, Unité Mixte de Recherche 8618, Centre National de la Recherche Scientifique, Univ Paris-Sud, 91405 Orsay Cedex, France.
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545
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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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546
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Wormuth D, Heiber I, Shaikali J, Kandlbinder A, Baier M, Dietz KJ. Redox regulation and antioxidative defence in Arabidopsis leaves viewed from a systems biology perspective. J Biotechnol 2007; 129:229-48. [PMID: 17207878 DOI: 10.1016/j.jbiotec.2006.12.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2006] [Revised: 11/11/2006] [Accepted: 12/04/2006] [Indexed: 12/18/2022]
Abstract
Redox regulation is a central control element in cell metabolism. It is employed to adjust photosynthesis and the antioxidant defence system of leaves to the prevailing environment. During recent years progress has been made in describing the redox-dependent alterations in metabolism, the thiol/disulfide proteome, the redox-dependent and cross-talking signalling pathways and the target genes of redox regulation. Some transcription factors have been identified as proteins that perform thiol/disulfide transitions linked to the redox-regulation of specific plant promoters. In addition first mathematical models have been designed to simulate antioxidant defence and predict its response. Taken together, a profound experimental data set has been generated which allows to approach a systems biology type of understanding of antioxidant defence in photosynthesising cells in the near future. Since oxidative stress is likely to limit plant growth under stress, such a systematic understanding of antioxidant defence will help to define novel targets for breeding stress-tolerant plants.
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Affiliation(s)
- Dennis Wormuth
- Biochemistry and Physiology of Plants, Faculty of Biology, W5, Bielefeld University, 33501 Bielefeld, Germany
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547
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Hajheidari M, Eivazi A, Buchanan BB, Wong JH, Majidi I, Salekdeh GH. Proteomics Uncovers a Role for Redox in Drought Tolerance in Wheat. J Proteome Res 2007; 6:1451-60. [PMID: 17343403 DOI: 10.1021/pr060570j] [Citation(s) in RCA: 153] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Proteomic analysis offers a new approach to identify a broad spectrum of genes that are expressed in living systems. We applied a proteomic approach to study changes in wheat grain in response to drought, a major environmental parameter adversely affecting development and crop yield. Three wheat genotypes differing in genetic background were cultivated in field under well-watered and drought conditions by following a randomized complete block design with four replications. The overall effect of drought was highly significant as determined by grain yield and total dry matter. About 650 spots were reproducibly detected and analyzed on 2-DE gels. Of these, 121 proteins showed significant change under drought condition in at least one of the genotypes. Mass spectrometry analysis using MALDI-TOF/TOF led to the identification of 57 proteins. Two-thirds of identified proteins were thioredoxin (Trx) targets, in accordance with the link between drought and oxidative stress. Further, because of contrasting changes in the tolerant and susceptible genotypes studied, several proteins emerge as key participants in the drought response. In addition to providing new information on the response to water deprivation, the present study offers opportunities to pursue the breeding of wheat with enhanced drought tolerance using identified candidate genetic markers. The 2-DE database of wheat seed proteins is available for public access at http://www.proteome.ir.
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Affiliation(s)
- Mohsen Hajheidari
- Department of Physiology and Proteomics, Agricultural Biotechnology Research, Institute of Iran, Karaj, Iran
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548
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Albrechtová JTP, Vervliet-Scheebaum M, Normann J, Veit J, Wagner E. Metabolic control of transcriptional-translational control loops (TTCL) by circadian oscillations in the redox- and phosphorylation state of cells. BIOL RHYTHM RES 2007. [DOI: 10.1080/09291010600804692] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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549
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Caporaletti D, D'Alessio AC, Rodriguez-Suarez RJ, Senn AM, Duek PD, Wolosiuk RA. Non-reductive modulation of chloroplast fructose-1,6-bisphosphatase by 2-Cys peroxiredoxin. Biochem Biophys Res Commun 2007; 355:722-7. [PMID: 17307139 DOI: 10.1016/j.bbrc.2007.02.013] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2007] [Accepted: 02/02/2007] [Indexed: 02/03/2023]
Abstract
2-Cys peroxiredoxin (2-Cys Prx) is a large group of proteins that participate in cell proliferation, differentiation, apoptosis, and photosynthesis. In the prevailing view, this ubiquitous peroxidase poises the concentration of H2O2 and, in so doing, regulates signal transduction pathways or protects macromolecules against oxidative damage. Here, we describe the first purification of 2-Cys Prx from higher plants and subsequently we show that the native and the recombinant forms of rapeseed leaves stimulate the activity of chloroplast fructose-1,6-bisphosphatase (CFBPase), a key enzyme of the photosynthetic CO2 assimilation. The absence of reductants, the strict requirement of both fructose 1,6-bisphosphate and Ca2+, and the response of single mutants C174S and C179S CFBPase bring forward clear differences with the well-known stimulation mediated by reduced thioredoxin via the regulatory 170's loop of CFBPase. Taken together, these findings provide an unprecedented insight into chloroplast enzyme regulation wherein both 2-Cys Prx and the 170's loop of CFBPase exhibit novel functions.
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Affiliation(s)
- Daniel Caporaletti
- Instituto Leloir, Patricias Argentinas 435, C1405BWE Buenos Aires, Argentina
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550
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Petros AK, Reddi AR, Kennedy ML, Hyslop AG, Gibney BR. Femtomolar Zn(II) affinity in a peptide-based ligand designed to model thiolate-rich metalloprotein active sites. Inorg Chem 2007; 45:9941-58. [PMID: 17140191 DOI: 10.1021/ic052190q] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Metal-ligand interactions are critical components of metalloprotein assembly, folding, stability, electrochemistry, and catalytic function. Research over the past 3 decades on the interaction of metals with peptide and protein ligands has progressed from the characterization of amino acid-metal and polypeptide-metal complexes to the design of folded protein scaffolds containing multiple metal cofactors. De novo metalloprotein design has emerged as a valuable tool both for the modular synthesis of these complex metalloproteins and for revealing the fundamental tenets of metalloprotein structure-function relationships. Our research has focused on using the coordination chemistry of de novo designed metalloproteins to probe the interactions of metal cofactors with protein ligands relevant to biological phenomena. Herein, we present a detailed thermodynamic analysis of Fe(II), Co(II), Zn(II), and[4Fe-4S]2(+/+) binding to IGA, a 16 amino acid peptide ligand containing four cysteine residues, H2N-KLCEGG-CIGCGAC-GGW-CONH2. These studies were conducted to delineate the inherent metal-ion preferences of this unfolded tetrathiolate peptide ligand as well as to evaluate the role of the solution pH on metal-peptide complex speciation. The [4Fe-4S]2(+/+)-IGA complex is both an excellent peptide-based synthetic analogue for natural ferredoxins and is flexible enough to accommodate mononuclear metal-ion binding. Incorporation of a single ferrous ion provides the FeII-IGA complex, a spectroscopic model of a reduced rubredoxin active site that possesses limited stability in aqueous buffers. As expected based on the Irving-Williams series and hard-soft acid-base theory, the Co(II) and Zn(II) complexes of IGA are significantly more stable than the Fe(II) complex. Direct proton competition experiments, coupled with determinations of the conditional dissociation constants over a range of pH values, fully define the thermodynamic stabilities and speciation of each MII-IGA complex. The data demonstrate that FeII-IGA and CoII-IGA have formation constant values of 5.0 x 10(8) and 4.2 x 10(11) M-1, which are highly attenuated at physiological pH values. The data also evince that the formation constant for ZnII-IGA is 8.0 x 10(15) M-1, a value that exceeds the tightest natural protein Zn(II)-binding affinities. The formation constant demonstrates that the metal-ligand binding energy of a ZnII(S-Cys)4 site can stabilize a metalloprotein by -21.6 kcal/mol. Rigorous thermodynamic analyses such as those demonstrated here are critical to current research efforts in metalloprotein design, metal-induced protein folding, and metal-ion trafficking.
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Affiliation(s)
- Amy K Petros
- Department of Chemistry, Columbia University, MC 3121, New York, New York 10027, USA
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