A Differential Redox Regulation of the Pathways Metabolizing Glyceraldehyde-3-Phosphate Tunes the Production of Reducing Power in the Cytosol of Plant Cells

Thiol-based redox regulation ensures light-responsive control of chloroplast functions. Light-derived signal is transferred in the form of reducing power from the photosynthetic electron transport chain to several redox-sensitive target proteins. Two types of protein, ferredoxin-thioredoxin reductase (FTR) and thioredoxin (Trx), are well recognized as the mediators of reducing power. However, it remains unclear which step in a series of redox-relay reactions is the critical bottleneck for determining the rate of target protein reduction. To address this, the redox behaviors of FTR, Trx, and target proteins were extensively characterized in vitro and in vivo. The FTR/Trx redox cascade was reconstituted in vitro using recombinant proteins from Arabidopsis. On the basis of this assay, we found that the FTR catalytic subunit and f-type Trx are rapidly reduced after the drive of reducing power transfer, irrespective of the presence or absence of their downstream target proteins. By contrast, three target proteins, fructose 1,6-bisphosphatase (FBPase), sedoheptulose 1,7-bisphosphatase (SBPase), and Rubisco activase (RCA) showed different reduction patterns; in particular, SBPase was reduced at a low rate. The in vivo study using Arabidopsis plants showed that the Trx family is commonly and rapidly reduced upon high light irradiation, whereas FBPase, SBPase, and RCA are differentially and slowly reduced. Both of these biochemical and physiological findings suggest that reducing power transfer from Trx to its target proteins is a rate-limiting step for chloroplast redox regulation, conferring distinct light-responsive redox behaviors on each of the targets.

Download Full-text

Biosynthesis of Sulfur-Containing Small Biomolecules in Plants

International Journal of Molecular Sciences ◽

10.3390/ijms21103470 ◽

2020 ◽

Vol 21 (10) ◽

pp. 3470 ◽

Cited By ~ 3

Author(s):

Yumi Nakai ◽

Akiko Maruyama-Nakashita

Keyword(s):

Redox Regulation ◽

Early Stage ◽

Plant Cells ◽

Essential Element ◽

Thiol Group ◽

Sulfur Transfer ◽

Transfer Processes ◽

Characteristic Features ◽

Small Biomolecules ◽

Sulfur Containing

Sulfur is an essential element required for plant growth. It can be found as a thiol group of proteins or non-protein molecules, and as various sulfur-containing small biomolecules, including iron-sulfur (Fe/S) clusters, molybdenum cofactor (Moco), and sulfur-modified nucleotides. Thiol-mediated redox regulation has been well investigated, whereas biosynthesis pathways of the sulfur-containing small biomolecules have not yet been clearly described. In order to understand overall sulfur transfer processes in plant cells, it is important to elucidate the relationships among various sulfur delivery pathways as well as to investigate their interactions. In this review, we summarize the information from recent studies on the biosynthesis pathways of several sulfur-containing small biomolecules and the proteins participating in these processes. In addition, we show characteristic features of gene expression in Arabidopsis at the early stage of sulfate depletion from the medium, and we provide insights into sulfur transfer processes in plant cells.

Download Full-text

Distinct electron transfer from ferredoxin–thioredoxin reductase to multiple thioredoxin isoforms in chloroplasts

Biochemical Journal ◽

10.1042/bcj20161089 ◽

2017 ◽

Vol 474 (8) ◽

pp. 1347-1360 ◽

Cited By ~ 31

Author(s):

Keisuke Yoshida ◽

Toru Hisabori

Keyword(s):

Electron Transfer ◽

Redox Regulation ◽

Thioredoxin Reductase ◽

Reducing Power ◽

Redox Potentials ◽

Regulation Network ◽

Electron Transfers ◽

Kinetics Of

Thiol-based redox regulation is considered to support light-responsive control of various chloroplast functions. The redox cascade via ferredoxin–thioredoxin reductase (FTR)/thioredoxin (Trx) has been recognized as a key to transmitting reducing power; however, Arabidopsis thaliana genome sequencing has revealed that as many as five Trx subtypes encoded by a total of 10 nuclear genes are targeted to chloroplasts. Because each Trx isoform seems to have a distinct target selectivity, the electron distribution from FTR to multiple Trxs is thought to be the critical branch point for determining the consequence of chloroplast redox regulation. In the present study, we aimed to comprehensively characterize the kinetics of electron transfer from FTR to 10 Trx isoforms. We prepared the recombinant FTR protein from Arabidopsis in the heterodimeric form containing the Fe–S cluster. By reconstituting the FTR/Trx system in vitro, we showed that FTR prepared here was enzymatically active and suitable for uncovering biochemical features of chloroplast redox regulation. A series of redox state determinations using the thiol-modifying reagent, 4-acetamido-4′-maleimidylstilbene-2,2′-disulfonate, indicated that all chloroplast Trx isoforms are commonly reduced by FTR; however, significantly different efficiencies were evident. These differences were apparently correlated with the distinct midpoint redox potentials among Trxs. Even when the experiments were performed under conditions of hypothetical in vivo stoichiometry of FTR and Trxs, a similar trend in distinguishable electron transfers was observed. These data highlight an aspect of highly organized circuits in the chloroplast redox regulation network.

Download Full-text

NTRC-dependent redox balance of 2-Cys peroxiredoxins is needed for optimal function of the photosynthetic apparatus

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1706003114 ◽

2017 ◽

Vol 114 (45) ◽

pp. 12069-12074 ◽

Cited By ~ 43

Author(s):

Juan Manuel Pérez-Ruiz ◽

Belén Naranjo ◽

Valle Ojeda ◽

Manuel Guinea ◽

Francisco Javier Cejudo

Keyword(s):

Redox Regulation ◽

Photosynthetic Apparatus ◽

Reducing Power ◽

Redox Balance ◽

Light Energy ◽

Energy Utilization ◽

Antioxidant Systems ◽

Redox Systems ◽

Triple Mutant ◽

Low Efficiency

Thiol-dependent redox regulation allows the rapid adaptation of chloroplast function to unpredictable changes in light intensity. Traditionally, it has been considered that chloroplast redox regulation relies on photosynthetically reduced ferredoxin (Fd), thioredoxins (Trxs), and an Fd-dependent Trx reductase (FTR), the Fd-FTR-Trxs system, which links redox regulation to light. More recently, a plastid-localized NADPH-dependent Trx reductase (NTR) with a joint Trx domain, termed NTRC, was identified. NTRC efficiently reduces 2-Cys peroxiredoxins (Prxs), thus having antioxidant function, but also participates in redox regulation of metabolic pathways previously established to be regulated by Trxs. Thus, the NTRC, 2-Cys Prxs, and Fd-FTR-Trxs redox systems may act concertedly, but the nature of the relationship between them is unknown. Here we show that decreased levels of 2-Cys Prxs suppress the phenotype of the Arabidopsis thaliana ntrc KO mutant. The excess of oxidized 2-Cys Prxs in NTRC-deficient plants drains reducing power from chloroplast Trxs, which results in low efficiency of light energy utilization and impaired redox regulation of Calvin–Benson cycle enzymes. Moreover, the dramatic phenotype of the ntrc-trxf1f2 triple mutant, lacking NTRC and f-type Trxs, was also suppressed by decreased 2-Cys Prxs contents, as the ntrc-trxf1f2-Δ2cp mutant partially recovered the efficiency of light energy utilization and exhibited WT rate of CO2 fixation and growth phenotype. The suppressor phenotype was not caused by compensatory effects of additional chloroplast antioxidant systems. It is proposed that the Fd-FTR-Trx and NTRC redox systems are linked by the redox balance of 2-Cys Prxs, which is crucial for chloroplast function.

Download Full-text

Redox regulation of chloroplastic G6PDH activity by thioredoxin occurs through structural changes modifying substrate accessibility and cofactor binding

Biochemical Journal ◽

10.1042/bj20130337 ◽

2013 ◽

Vol 457 (1) ◽

pp. 117-125 ◽

Cited By ~ 12

Author(s):

Guillaume Née ◽

Magali Aumont-Nicaise ◽

Mirko Zaffagnini ◽

Sylvie Nessler ◽

Marielle Valerio-Lepiniec ◽

...

Keyword(s):

Active Site ◽

Redox Regulation ◽

Structural Changes ◽

Reducing Power ◽

G6pdh Activity ◽

Metabolic Processes ◽

Cofactor Binding ◽

Glucose 6 Phosphate Dehydrogenase

G6PDH (glucose-6-phosphate dehydrogenase) generates NADPH used as reducing power in many metabolic processes. We studied the mechanism by which thioredoxin redox regulates plastidial Arabidopsis G6PDH1 activity and found that it changes substrate accessibility and cofactor binding to its active site.

Download Full-text

Redox signals as a language of interorganellar communication in plant cells

Open Life Sciences ◽

10.2478/s11535-013-0243-4 ◽

2013 ◽

Vol 8 (12) ◽

pp. 1153-1163 ◽

Cited By ~ 3

Author(s):

Tomasz Kopczewski ◽

Elżbieta Kuźniak

Keyword(s):

Redox Regulation ◽

Biological Effects ◽

Physiological Responses ◽

Plant Cells ◽

Enzymatic Antioxidants ◽

Oxygen Species ◽

Redox Systems ◽

Disulfide Exchange ◽

Redox Active

AbstractPlants are redox systems and redox-active compounds control and regulate all aspects of their life. Recent studies have shown that changes in reactive oxygen species (ROS) concentration mediated by enzymatic and non-enzymatic antioxidants are transferred into redox signals used by plants to activate various physiological responses. An overview of the main antioxidants and redox signaling in plant cells is presented. In this review, the biological effects of ROS and related redox signals are discussed in the context of acclimation to changing environmental conditions. Special attention is paid to the role of thiol/disulfide exchange via thioredoxins (Trxs), glutaredoxins (Grxs) and peroxiredoxins (Prxs) in the redox regulatory network. In plants, chloroplasts and mitochondria occupying a chloroplasts and mitochondria play key roles in cellular metabolism as well as in redox regulation and signaling. The integrated redox functions of these organelles are discussed with emphasis on the importance of the chloroplast and mitochondrion to the nucleus retrograde signaling in acclimatory and stress response.

Download Full-text

Up-regulation of bundle sheath electron transport capacity under limiting light in C4Setaria viridis

10.1101/2021.02.10.430537 ◽

2021 ◽

Author(s):

Maria Ermakova ◽

Chandra Bellasio ◽

Duncan Fitzpatrick ◽

Robert T. Furbank ◽

Fikret Mamedov ◽

...

Keyword(s):

Electron Transport ◽

Photosystem Ii ◽

Redox Regulation ◽

Light Harvesting ◽

Electron Flow ◽

Crop Improvement ◽

Reducing Power ◽

Bundle Sheath ◽

Transport Capacity ◽

Shade Acclimation

AbstractC4 photosynthesis is a biochemical pathway that operates across mesophyll and bundle sheath (BS) cells to increase CO2 concentration at the site of CO2 fixation. C4 plants benefit from high irradiance but their efficiency decreases under shade causing a loss of productivity in crop canopies. We investigated shade acclimation responses of a model NADP-ME monocot Setaria viridis focussing on cell-specific electron transport capacity. Plants grown under low light (LL) maintained CO2 assimilation rates similar to high light plants but had an increased chlorophyll and light-harvesting-protein content, predominantly in BS cells. Photosystem II (PSII) protein abundance, oxygen-evolving activity and the PSII/PSI ratio all increased in LL BS cells indicating a higher capacity for linear electron flow. PSI, ATP synthase, Cytochrome b6f and the chloroplastic NAD(P) dehydrogenase complex, which constitute the BS cyclic electron flow machinery, were all upregulated in LL plants. A decline in PEP carboxylase activity in mesophyll cells and a consequent shortage of reducing power in BS chloroplasts was associated with the more oxidised redox state of the plastoquinone pool in LL plants and the formation of PSII - light-harvesting complex II supercomplexes with an increased oxygen evolution rate. Our results provide evidence of a redox regulation of the supramolecular composition of Photosystem II in BS cells in response to shading. This newly identified link contributes to understanding the regulation of PSII activity in C4 plants and will support strategies for crop improvement including the engineering of C4 photosynthesis into C3 plants.Significance statementThe efficiency of C4 photosynthesis decreases under low irradiance causing a loss of productivity in crop canopies. We investigate shade acclimation of a model NADP-ME monocot, analysing cell-specific protein expression and electron transport capacity. We propose a regulatory pathway controlling abundance and activity of Photosystem II in bundle sheath cells in response to irradiance.

Download Full-text

Thioredoxin regulates G6PDH activity by changing redox states of OpcA in the nitrogen-fixing cyanobacterium Anabaena sp. PCC 7120

Biochemical Journal ◽

10.1042/bcj20170869 ◽

2018 ◽

Vol 475 (6) ◽

pp. 1091-1105 ◽

Cited By ~ 7

Author(s):

Shoko Mihara ◽

Hitomi Wakao ◽

Keisuke Yoshida ◽

Akiyoshi Higo ◽

Kazunori Sugiura ◽

...

Keyword(s):

Redox Regulation ◽

Reducing Power ◽

Spectrometric Analysis ◽

Nitrogen Fixing ◽

G6pdh Activity ◽

Redox States ◽

Anabaena 7120 ◽

Cyanobacterium Anabaena ◽

Anabaena Sp ◽

Pcc 7120

Glucose 6-phosphate dehydrogenase (G6PDH) catalyzes the first reaction in the oxidative pentose phosphate pathway. In green plant chloroplasts, G6PDH is a unique redox-regulated enzyme, since it is inactivated under the reducing conditions. This regulation is accomplished using a redox-active cysteine pair, which is conserved in plant G6PDH. The inactivation of this enzyme under conditions of light must be beneficial to prevent release of CO2 from the photosynthetic carbon fixation cycle. In the filamentous, heterocyst-forming, nitrogen-fixing cyanobacterium Anabaena sp. PCC 7120 (Anabaena 7120), G6PDH plays a pivotal role in providing reducing power for nitrogenase, and its activity is also reported to be suppressed by reduction, though Anabaena G6PDH does not conserve the critical cysteines for regulation. Based on the thorough analyses of the redox regulation mechanisms of G6PDH from Anabaena 7120 and its activator protein OpcA, we found that m-type thioredoxin regulates G6PDH activity by changing the redox states of OpcA. Mass spectrometric analysis and mutagenesis studies indicate that Cys393 and Cys399 of OpcA are responsible for the redox regulation property of this protein. Moreover, in vivo analyses of the redox states of OpcA showed that more than half of the OpcA is present as an oxidized form, even under conditions of light, when cells are cultured under the nitrogen-fixing conditions. This redox regulation of OpcA might be necessary to provide reducing power for nitrogenase by G6PDH in heterocysts even during the day.

Download Full-text

Autophagy Is Involved in the Viability of Overexpressing Thioredoxin o1 Tobacco BY-2 Cells under Oxidative Conditions

Antioxidants ◽

10.3390/antiox10121884 ◽

2021 ◽

Vol 10 (12) ◽

pp. 1884

Author(s):

Sabrina De Brasi-Velasco ◽

Omar López-Vidal ◽

María Carmen Martí ◽

Ana Ortiz-Espín ◽

Francisca Sevilla ◽

...

Keyword(s):

Gene Expression ◽

Redox Regulation ◽

Plant Cells ◽

Dot Blot ◽

Functional Interaction ◽

H2o2 Treatment ◽

Useful Components ◽

In Vitro Interaction

Autophagy is an essential process for the degradation of non-useful components, although the mechanism involved in its regulation is less known in plants than in animal systems. Redox regulation of autophagy components is emerging as a possible key mechanism with thioredoxins (TRXs) proposed as involved candidates. In this work, using overexpressing PsTRXo1 tobacco cells (OEX), which present higher viability than non-overexpressing cells after H2O2 treatment, we examine the functional interaction of autophagy and PsTRXo1 in a collaborative response. OEX cells present higher gene expression of the ATG (Autophagy related) marker ATG4 and higher protein content of ATG4, ATG8, and lipidated ATG8 as well as higher ATG4 activity than control cells, supporting the involvement of autophagy in their response to H2O2. In this oxidative situation, autophagy occurs in OEX cells as is evident from an accumulation of autolysosomes and ATG8 immunolocalization when the E-64d autophagy inhibitor is used. Interestingly, cell viability decreases in the presence of the inhibitor, pointing to autophagy as being involved in cell survival. The in vitro interaction of ATG4 and PsTRXo1 proteins is confirmed by dot-blot and co-immunoprecipitation assays as well as the redox regulation of ATG4 activity by PsTRXo1. These findings extend the role of TRXs in mediating the redox regulation of the autophagy process in plant cells.

Download Full-text

The chloroplast 2-cysteine peroxiredoxin functions as thioredoxin oxidase in redox regulation of chloroplast metabolism

10.1101/317107 ◽

2018 ◽

Author(s):

Mohamad-Javad Vaseghi ◽

Kamel Chibani ◽

Wilena Telman ◽

Michael Liebthal ◽

Melanie Gerken ◽

...

Keyword(s):

Redox Regulation ◽

Plant Cells ◽

Decisive Role ◽

Oxidative Inactivation ◽

Fluctuating Light ◽

Fructose 1,6 Bisphosphatase ◽

Chloroplast Metabolism ◽

Electron Sink ◽

Kinetics Of

AbstractThiol-dependent redox regulation controls central processes in plant cells including photosynthesis. Thioredoxins reductively activate e.g. Calvin-Benson cycle enzymes. However the mechanism of oxidative inactivation is unknown despite its importance for efficient regulation. Here, the abundant 2-cysteine peroxiredoxin (2-CysPrx), but not its site-directed variants, mediates rapid inactivation of reductively activated fructose-1,6-bisphosphatase and NADPH-dependent malate dehydrogenase (MDH) in the presence of the proper thioredoxins. Deactivation of phosphoribulokinase and MDH was compromised in 2cysprxAB mutants plants upon light/dark transition compared to wildtype. The decisive role of 2cysprxAB in regulating photosynthesis was evident from reoxidation kinetics of ferredoxin upon darkening of intact leaves since its half time decreased 3.5-times in 2cysprxAB. The disadvantage of inefficient deactivation turned into an advantage in fluctuating light. The results show that the 2-CysPrx serves as electron sink in the thiol network important to oxidize reductively activated proteins and represents the missing link in the reversal of thioredoxin-dependent regulation.

Download Full-text