Thioredoxin-dependent regulatory networks in chloroplasts under fluctuating light conditions

Plants have adopted a number of mechanisms to restore redox homeostasis in the chloroplast under fluctuating light conditions in nature. Chloroplast thioredoxin systems are crucial components of this redox network, mediating environmental signals to chloroplast proteins. In the reduced state, thioredoxins control the structure and function of proteins by reducing disulfide bridges in the redox active site of a protein. Subsequently, an oxidized thioredoxin is reduced by a thioredoxin reductase, the two enzymes together forming a thioredoxin system. Plant chloroplasts have versatile thioredoxin systems, including two reductases dependent on ferredoxin and NADPH as reducing power, respectively, several types of thioredoxins, and the system to deliver thiol redox signals to the thylakoid membrane and lumen. Light controls the activity of chloroplast thioredoxin systems in two ways. First, light reactions activate the thioredoxin systems via donation of electrons to oxidized ferredoxin and NADP + , and second, light induces production of reactive oxygen species in chloroplasts which deactivate the components of the thiol redox network. The diversity and partial redundancy of chloroplast thioredoxin systems enable chloroplast metabolism to rapidly respond to ever-changing environmental conditions and to raise plant fitness in natural growth conditions.

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Cell Signaling with Extracellular Thioredoxin and Thioredoxin-Like Proteins: Insight into Their Mechanisms of Action

Oxidative Medicine and Cellular Longevity ◽

10.1155/2017/8475125 ◽

2017 ◽

Vol 2017 ◽

pp. 1-11 ◽

Cited By ~ 10

Author(s):

Thierry Léveillard ◽

Najate Aït-Ali

Keyword(s):

Communication Systems ◽

Intron Retention ◽

Single Gene ◽

Redox Homeostasis ◽

Cell Communication ◽

Thioredoxin Reductase ◽

Reducing Power ◽

Pentose Phosphate ◽

Adult T Cell Leukemia ◽

Thioredoxin System

Thioredoxins are small thiol-oxidoreductase enzymes that control cellular redox homeostasis. Paradoxically, human thioredoxin (TXN1) was first identified as the adult T cell leukemia-derived factor (ADF), a secreted protein. ADF has been implicated in a wide variety of cell-to-cell communication systems acting as a cytokine or a chemokine. TRX80 is a truncated TXN1 protein with cytokine activity. The unconventional secretion mechanism of these extracellular thioredoxins is unknown. The thioredoxin system is relying on glucose metabolism through the pentose phosphate pathway that provides reducing power in the form of NADPH, the cofactor of thioredoxin reductase (TXNRD). While a complete extracellular TXN system is present in the blood in the form of circulating TXN1 and TXNDR1, the source of extracellular NADPH remains a mystery. In the absence of redox regenerating capacity, extracellular thioredoxins may rather be prooxidant agents. Rod-derived cone viability factor (RdCVF) is the product of intron retention of the nucleoredoxin-like 1 (NXNL1) gene, a secreted truncated thioredoxin-like protein. The other product encoded by the gene, RdCVFL, is an enzymatically active thioredoxin. This is a very singular example of positive feedback of a superthioredoxin system encoded by a single gene likely emerging during evolution from metabolic constraints on redox signaling.

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Overlapping Roles of the Cytoplasmic and Mitochondrial Redox Regulatory Systems in the Yeast Saccharomyces cerevisiae

Eukaryotic Cell ◽

10.1128/ec.4.2.392-400.2005 ◽

2005 ◽

Vol 4 (2) ◽

pp. 392-400 ◽

Cited By ~ 60

Author(s):

Eleanor W. Trotter ◽

Chris M. Grant

Keyword(s):

Oxidative Stress ◽

Saccharomyces Cerevisiae ◽

Redox State ◽

Redox Homeostasis ◽

Thioredoxin Reductase ◽

Normal Growth ◽

Growth Conditions ◽

Reduced Form ◽

Yeast Saccharomyces Cerevisiae ◽

Thioredoxin System

ABSTRACT Thioredoxins are small, highly conserved oxidoreductases which are required to maintain the redox homeostasis of the cell. Saccharomyces cerevisiae contains a cytoplasmic thioredoxin system (TRX1, TRX2, and TRR1) as well as a complete mitochondrial thioredoxin system, comprising a thioredoxin (TRX3) and a thioredoxin reductase (TRR2). In the present study we have analyzed the functional overlap between the two systems. By constructing mutant strains with deletions of both the mitochondrial and cytoplasmic systems (trr1 trr2 and trx1 trx2 trx3), we show that cells can survive in the absence of both systems. Analysis of the redox state of the cytoplasmic thioredoxins reveals that they are maintained independently of the mitochondrial system. Similarly, analysis of the redox state of Trx3 reveals that it is maintained in the reduced form in wild-type cells and in mutants lacking components of the cytoplasmic thioredoxin system (trx1 trx2 or trr1). Surprisingly, the redox state of Trx3 is also unaffected by the loss of the mitochondrial thioredoxin reductase (trr2) and is largely maintained in the reduced form unless cells are exposed to an oxidative stress. Since glutathione reductase (Glr1) has been shown to colocalize to the cytoplasm and mitochondria, we examined whether loss of GLR1 influences the redox state of Trx3. During normal growth conditions, deletion of TRR2 and GLR1 was found to result in partial oxidation of Trx3, indicating that both Trr2 and Glr1 are required to maintain the redox state of Trx3. The oxidation of Trx3 in this double mutant is even more pronounced during oxidative stress or respiratory growth conditions. Taken together, these data indicate that Glr1 and Trr2 have an overlapping function in the mitochondria.

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Fluctuating light experiments and semi-automated plant phenotyping enabled by self-built growth racks and simple upgrades to the IMAGING-PAM

Plant Methods ◽

10.1186/s13007-019-0546-1 ◽

2019 ◽

Vol 15 (1) ◽

Cited By ~ 1

Author(s):

Dominik Schneider ◽

Laura S. Lopez ◽

Meng Li ◽

Joseph D. Crawford ◽

Helmut Kirchhoff ◽

...

Keyword(s):

Data Analysis ◽

Low Cost ◽

Growth Conditions ◽

Research Field ◽

Constant Light ◽

Plant Phenotyping ◽

Natural Light ◽

Light Conditions ◽

Fluctuating Light ◽

Science Labs

Abstract Background Over the last years, several plant science labs have started to employ fluctuating growth light conditions to simulate natural light regimes more closely. Many plant mutants reveal quantifiable effects under fluctuating light despite being indistinguishable from wild-type plants under standard constant light. Moreover, many subtle plant phenotypes become intensified and thus can be studied in more detail. This observation has caused a paradigm shift within the photosynthesis research community and an increasing number of scientists are interested in using fluctuating light growth conditions. However, high installation costs for commercial controllable LED setups as well as costly phenotyping equipment can make it hard for small academic groups to compete in this emerging field. Results We show a simple do-it-yourself approach to enable fluctuating light growth experiments. Our results using previously published fluctuating light sensitive mutants, stn7 and pgr5, confirm that our low-cost setup yields similar results as top-prized commercial growth regimes. Moreover, we show how we increased the throughput of our Walz IMAGING-PAM, also found in many other departments around the world. We have designed a Python and R-based open source toolkit that allows for semi-automated sample segmentation and data analysis thereby reducing the processing bottleneck of large experimental datasets. We provide detailed instructions on how to build and functionally test each setup. Conclusions With material costs well below USD$1000, it is possible to setup a fluctuating light rack including a constant light control shelf for comparison. This allows more scientists to perform experiments closer to natural light conditions and contribute to an emerging research field. A small addition to the IMAGING-PAM hardware not only increases sample throughput but also enables larger-scale plant phenotyping with automated data analysis.

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Auranofin exerts broad-spectrum bactericidal activities by targeting thiol-redox homeostasis

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1504022112 ◽

2015 ◽

Vol 112 (14) ◽

pp. 4453-4458 ◽

Cited By ~ 129

Author(s):

Michael B. Harbut ◽

Catherine Vilchèze ◽

Xiaozhou Luo ◽

Mary E. Hensler ◽

Hui Guo ◽

...

Keyword(s):

Redox Homeostasis ◽

Thioredoxin Reductase ◽

Redox Balance ◽

Resistant Bacteria ◽

Gram Positive ◽

Antibiotic Resistant ◽

Gram Positive Bacteria ◽

Bactericidal Activities ◽

Orally Bioavailable ◽

Thiol Redox

Infections caused by antibiotic-resistant bacteria are a rising public health threat and make the identification of new antibiotics a priority. From a cell-based screen for bactericidal compounds againstMycobacterium tuberculosisunder nutrient-deprivation conditions we identified auranofin, an orally bioavailable FDA-approved antirheumatic drug, as having potent bactericidal activities against both replicating and nonreplicatingM. tuberculosis. We also found that auranofin is active against other Gram-positive bacteria, includingBacillus subtilisandEnterococcus faecalis, and drug-sensitive and drug-resistant strains ofEnterococcus faeciumandStaphylococcus aureus. Our biochemical studies showed that auranofin inhibits the bacterial thioredoxin reductase, a protein essential in many Gram-positive bacteria for maintaining the thiol-redox balance and protecting against reactive oxidative species. Auranofin decreases the reducing capacity of target bacteria, thereby sensitizing them to oxidative stress. Finally, auranofin was efficacious in a murine model of methicillin-resistantS. aureusinfection. These results suggest that the thioredoxin-mediated redox cascade of Gram-positive pathogens is a valid target for the development of antibacterial drugs, and that the existing clinical agent auranofin may be repurposed to aid in the treatment of several important antibiotic-resistant pathogens.

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Fluctuating light experiments and semi-automated plant phenotyping enabled by self-built growth racks and simple upgrades to the IMAGING-PAM

10.1101/795476 ◽

2019 ◽

Cited By ~ 1

Author(s):

Dominik Schneider ◽

Laura S. Lopez ◽

Meng Li ◽

Joseph D. Crawford ◽

Helmut Kirchhoff ◽

...

Keyword(s):

Data Analysis ◽

Low Cost ◽

Growth Conditions ◽

Research Field ◽

Constant Light ◽

Plant Phenotyping ◽

Natural Light ◽

Light Conditions ◽

Fluctuating Light ◽

Science Labs

AbstractBackgroundOver the last years, several plant science labs have started to employ fluctuating growth light conditions to simulate natural light regimes more closely. Many plant mutants reveal quantifiable effects under fluctuating light despite being indistinguishable from wild-type plants under standard constant light. Moreover, many subtle plant phenotypes become intensified and thus can be studied in more detail. This observation has caused a paradigm shift within the photosynthesis research community and an increasing number of scientists are interested in using fluctuating light growth conditions. However, high installation costs for commercial controllable LED setups as well as costly phenotyping equipment can make it hard for small academic groups to compete in this emerging field.ResultsWe show a simple do-it-yourself approach to enable fluctuating light growth experiments. Our results using previously published fluctuating light sensitive mutants, stn7 and pgr5, confirm that our low-cost setup yields similar results as top-prized commercial growth regimes. Moreover, we show how we increased the throughput of our Walz IMAGING-PAM, also found in many other departments around the world. We have designed a Python and R-based open source toolkit that allows for semi-automated sample segmentation and data analysis thereby reducing the processing bottleneck of large experimental datasets. We provide detailed instructions on how to build and functionally test each setup.ConclusionsWith material costs well below USD$1000, it is possible to setup a fluctuating light rack including a constant light control shelf for comparison. This allows more scientists to perform experiments closer to natural light conditions and contribute to an emerging research field. A small addition to the IMAGING-PAM hardware not only increases sample throughput but also enables larger-scale plant phenotyping with automated data analysis.

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Redox Systems in Botrytis cinerea: Impact on Development and Virulence

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-01-14-0012-r ◽

2014 ◽

Vol 27 (8) ◽

pp. 858-874 ◽

Cited By ~ 34

Author(s):

Anne Viefhues ◽

Jens Heller ◽

Nora Temme ◽

Paul Tudzynski

Keyword(s):

Botrytis Cinerea ◽

Redox Homeostasis ◽

Thioredoxin Reductase ◽

Redox System ◽

Redox Status ◽

Redox Systems ◽

Gene Encoding ◽

Cellular Redox ◽

Thioredoxin System ◽

The Impact

The thioredoxin system is of great importance for maintenance of cellular redox homeostasis. Here, we show that it has a severe influence on virulence of Botrytis cinerea, demonstrating that redox processes are important for host-pathogen interactions in this necrotrophic plant pathogen. The thioredoxin system is composed of two enzymes, the thioredoxin and the thioredoxin reductase. We identified two genes encoding for thioredoxins (bctrx1, bctrx2) and one gene encoding for a thioredoxin reductase (bctrr1) in the genome of B. cinerea. Knockout mutants of bctrx1 and bctrr1 were severely impaired in virulence and more sensitive to oxidative stress. Additionally, Δbctrr1 showed enhanced H2O2 production and retarded growth. To investigate the impact of the second major cellular redox system, glutathione, we generated deletion mutants for two glutathione reductase genes. The effects were only marginal; deletion of bcglr1 resulted in reduced germination and, correspondingly, to retarded infection as well as reduced growth on minimal medium, whereas bcglr2 deletion had no distinctive phenotype. In summary, we showed that the balanced redox status maintained by the thioredoxin system is essential for development and pathogenesis of B. cinerea, whereas the second major cellular redox system, the glutathione system, seems to have only minor impact on these processes.

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Staphylococcus aureus NrdH Redoxin Is a Reductant of the Class Ib Ribonucleotide Reductase

Journal of Bacteriology ◽

10.1128/jb.00539-10 ◽

2010 ◽

Vol 192 (19) ◽

pp. 4963-4972 ◽

Cited By ~ 22

Author(s):

Inbal Rabinovitch ◽

Michaela Yanku ◽

Adva Yeheskel ◽

Gerald Cohen ◽

Ilya Borovok ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Ribonucleotide Reductase ◽

Thioredoxin Reductase ◽

Reducing Power ◽

Anaerobic Growth ◽

Structural Motif ◽

Thiol Redox ◽

Class Ib

ABSTRACT Staphylococci contain a class Ib NrdEF ribonucleotide reductase (RNR) that is responsible, under aerobic conditions, for the synthesis of deoxyribonucleotide precursors for DNA synthesis and repair. The genes encoding that RNR are contained in an operon consisting of three genes, nrdIEF, whereas many other class Ib RNR operons contain a fourth gene, nrdH, that determines a thiol redoxin protein, NrdH. We identified a 77-amino-acid open reading frame in Staphylococcus aureus that resembles NrdH proteins. However, S. aureus NrdH differs significantly from the canonical NrdH both in its redox-active site, C-P-P-C instead of C-M/V-Q-C, and in the absence of the C-terminal [WF]SGFRP[DE] structural motif. We show that S. aureus NrdH is a thiol redox protein. It is not essential for aerobic or anaerobic growth and appears to have a marginal role in protection against oxidative stress. In vitro, S. aureus NrdH was found to be an efficient reductant of disulfide bonds in low-molecular-weight substrates and proteins using dithiothreitol as the source of reducing power and an effective reductant for the homologous class Ib RNR employing thioredoxin reductase and NADPH as the source of the reducing power. Its ability to reduce NrdEF is comparable to that of thioredoxin-thioredoxin reductase. Hence, S. aureus contains two alternative thiol redox proteins, NrdH and thioredoxin, with both proteins being able to function in vitro with thioredoxin reductase as the immediate hydrogen donors for the class Ib RNR. It remains to be clarified under which in vivo physiological conditions the two systems are used.

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Regulation of cyclic electron flow by chloroplast NADPH-dependent thioredoxin system

10.1101/261560 ◽

2018 ◽

Author(s):

Lauri Nikkanen ◽

Jouni Toivola ◽

Andrea Trotta ◽

Manuel Guinea Diaz ◽

Mikko Tikkanen ◽

...

Keyword(s):

Carbon Fixation ◽

Electron Flow ◽

Proton Pumping ◽

Cyclic Electron Flow ◽

Light Conditions ◽

Oxidoreductase Activity ◽

Atp Production ◽

Fluctuating Light ◽

Thioredoxin System

ABSTRACTLinear electron transport in the thylakoid membrane drives both photosynthetic NADPH and ATP production, while cyclic electron flow (CEF) around photosystem I only promotes the translocation of protons from stroma to thylakoid lumen. The chloroplast NADH-dehydrogenase-like complex (NDH) participates in one CEF route transferring electrons from ferredoxin back to the plastoquinone pool with concomitant proton pumping to the lumen. CEF has been proposed to balance the ratio of ATP/NADPH production and to control the redox poise particularly in fluctuating light conditions, but the mechanisms regulating the NDH complex remain unknown. We have investigated potential regulation of the CEF pathways by the chloroplast NADPH-thioredoxin reductase (NTRC) in vivo by using an Arabidopsis knockout line of NTRC as well as lines overexpressing NTRC. Here we present biochemical and biophysical evidence showing that NTRC activates the NDH-dependent CEF and regulates the generation of proton motive force, thylakoid conductivity to protons and redox balance between the thylakoid electron transfer chain and the stroma during changes in light conditions. Further, protein–protein interaction assays suggest a putative thioredoxin-target site in close proximity to the ferredoxin binding domain of NDH, thus providing a plausible mechanism for regulation of the NDH ferredoxin:plastoquinone oxidoreductase activity by NTRC.One sentence summaryChloroplast thioredoxins regulate photosynthetic cyclic electron flow that balances the activities of light and carbon fixation reactions and improves plant fitness under fluctuating light conditions.

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Mycobacterium tuberculosis Thioredoxin Reductase Is Essential for Thiol Redox Homeostasis but Plays a Minor Role in Antioxidant Defense

PLoS Pathogens ◽

10.1371/journal.ppat.1005675 ◽

2016 ◽

Vol 12 (6) ◽

pp. e1005675 ◽

Cited By ~ 31

Author(s):

Kan Lin ◽

Kathryn M. O'Brien ◽

Carolina Trujillo ◽

Ruojun Wang ◽

Joshua B. Wallach ◽

...

Keyword(s):

Mycobacterium Tuberculosis ◽

Antioxidant Defense ◽

Redox Homeostasis ◽

Thioredoxin Reductase ◽

Minor Role ◽

Thiol Redox ◽

A Minor

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NTRC Effects on Non-Photochemical Quenching Depends on PGR5

Antioxidants ◽

10.3390/antiox10060900 ◽

2021 ◽

Vol 10 (6) ◽

pp. 900

Author(s):

Belen Naranjo ◽

Jan-Ferdinand Penzler ◽

Thilo Rühle ◽

Dario Leister

Keyword(s):

Steady State ◽

Electron Flow ◽

Thioredoxin Reductase ◽

Energy Utilization ◽

Photochemical Quenching ◽

Additive Effects ◽

Light Conditions ◽

Fluctuating Light ◽

Non Photochemical Quenching ◽

Transient And Steady State

Non-photochemical quenching (NPQ) protects plants from the detrimental effects of excess light. NPQ is rapidly induced by the trans-thylakoid proton gradient during photosynthesis, which in turn requires PGR5/PGRL1-dependent cyclic electron flow (CEF). Thus, Arabidopsis thaliana plants lacking either protein cannot induce transient NPQ and die under fluctuating light conditions. Conversely, the NADPH-dependent thioredoxin reductase C (NTRC) is required for efficient energy utilization and plant growth, and in its absence, transient and steady-state NPQ is drastically increased. How NTRC influences NPQ and functionally interacts with CEF is unclear. Therefore, we generated the A. thaliana line pgr5 ntrc, and found that the inactivation of PGR5 suppresses the high transient and steady-state NPQ and impaired growth phenotypes observed in the ntrc mutant under short-day conditions. This implies that NTRC negatively influences PGR5 activity and, accordingly, the lack of NTRC is associated with decreased levels of PGR5, possibly pointing to a mechanism to restrict upregulation of PGR5 activity in the absence of NTRC. When exposed to high light intensities, pgr5 ntrc plants display extremely impaired photosynthesis and growth, indicating additive effects of lack of both proteins. Taken together, these findings suggest that the interplay between NTRC and PGR5 is relevant for photoprotection and that NTRC might regulate PGR5 activity.

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