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Yoshida K, Hisabori T. Divergent Protein Redox Dynamics and Their Relationship with Electron Transport Efficiency during Photosynthesis Induction. PLANT & CELL PHYSIOLOGY 2024; 65:737-747. [PMID: 38305687 PMCID: PMC11138366 DOI: 10.1093/pcp/pcae013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2023] [Revised: 01/08/2024] [Accepted: 01/31/2024] [Indexed: 02/03/2024]
Abstract
Various chloroplast proteins are activated/deactivated during the light/dark cycle via the redox regulation system. Although the photosynthetic electron transport chain provides reducing power to redox-sensitive proteins via the ferredoxin (Fd)/thioredoxin (Trx) pathway for their enzymatic activity control, how the redox states of individual proteins are linked to electron transport efficiency remains uncharacterized. Here we addressed this subject with a focus on the photosynthetic induction phase. We used Arabidopsis plants, in which the amount of Fd-Trx reductase (FTR), a core component in the Fd/Trx pathway, was genetically altered. Several chloroplast proteins showed different redox shift responses toward low- and high-light treatments. The light-dependent reduction of Calvin-Benson cycle enzymes fructose 1,6-bisphosphatase (FBPase) and sedoheptulose 1,7-bisphosphatase (SBPase) was partially impaired in the FTR-knockdown ftrb mutant. Simultaneous analyses of chlorophyll fluorescence and P700 absorbance change indicated that the induction of the electron transport reactions was delayed in the ftrb mutant. FTR overexpression also mildly affected the reduction patterns of FBPase and SBPase under high-light conditions, which were accompanied by the modification of electron transport properties. Accordingly, the redox states of FBPase and SBPase were linearly correlated with electron transport rates. In contrast, ATP synthase was highly reduced even when electron transport reactions were not fully induced. Furthermore, the redox response of proton gradient regulation 5-like photosynthetic phenotype1 (PGRL1; a protein involved in cyclic electron transport) did not correlate with electron transport rates. Our results provide insights into the working dynamics of the redox regulation system and their differential associations with photosynthetic electron transport efficiency.
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Affiliation(s)
- Keisuke Yoshida
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Nagatsuta-cho 4259, Midori-ku, Yokohama, 226-8501 Japan
| | - Toru Hisabori
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Nagatsuta-cho 4259, Midori-ku, Yokohama, 226-8501 Japan
- Internantional Research Frontiers Initiative, Tokyo Institute of Technology, Nagatsuta-cho 4259, Midori-ku, Yokohama, 226-8501 Japan
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2
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Fukushi Y, Yokochi Y, Hisabori T, Yoshida K. Overexpression of thioredoxin-like protein ACHT2 leads to negative feedback control of photosynthesis in Arabidopsis thaliana. JOURNAL OF PLANT RESEARCH 2024; 137:445-453. [PMID: 38367196 PMCID: PMC11082001 DOI: 10.1007/s10265-024-01519-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Accepted: 01/04/2024] [Indexed: 02/19/2024]
Abstract
Thioredoxin (Trx) is a small redox mediator protein involved in the regulation of various chloroplast functions by modulating the redox state of Trx target proteins in ever-changing light environments. Using reducing equivalents produced by the photosynthetic electron transport chain, Trx reduces the disulfide bonds on target proteins and generally turns on their activities. While the details of the protein-reduction mechanism by Trx have been well investigated, the oxidation mechanism that counteracts it has long been unclear. We have recently demonstrated that Trx-like proteins such as Trx-like2 and atypical Cys His-rich Trx (ACHT) can function as protein oxidation factors in chloroplasts. Our latest study on transgenic Arabidopsis plants indicated that the ACHT isoform ACHT2 is involved in regulating the thermal dissipation of light energy. To understand the role of ACHT2 in vivo, we characterized phenotypic changes specifically caused by ACHT2 overexpression in Arabidopsis. ACHT2-overexpressing plants showed growth defects, especially under high light conditions. This growth phenotype was accompanied with the impaired reductive activation of Calvin-Benson cycle enzymes, enhanced thermal dissipation of light energy, and decreased photosystem II activity. Overall, ACHT2 overexpression promoted protein oxidation that led to the inadequate activation of Calvin-Benson cycle enzymes in light and consequently induced negative feedback control of the photosynthetic electron transport chain. This study highlights the importance of the balance between protein reduction and oxidation in chloroplasts for optimal photosynthetic performance and plant growth.
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Affiliation(s)
- Yuka Fukushi
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, 226-8501, Japan
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, 226-8501, Japan
| | - Yuichi Yokochi
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, 226-8501, Japan
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, 226-8501, Japan
| | - Toru Hisabori
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, 226-8501, Japan
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, 226-8501, Japan
- International Research Frontier Initiative, Tokyo Institute of Technology, Yokohama, 226-8501, Japan
| | - Keisuke Yoshida
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, 226-8501, Japan.
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, 226-8501, Japan.
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3
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Hoh D, Froehlich JE, Kramer DM. Redox regulation in chloroplast thylakoid lumen: The pmf changes everything, again. PLANT, CELL & ENVIRONMENT 2023. [PMID: 38111217 DOI: 10.1111/pce.14789] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Revised: 11/28/2023] [Accepted: 12/05/2023] [Indexed: 12/20/2023]
Abstract
Photosynthesis is the foundation of life on Earth. However, if not well regulated, it can also generate excessive reactive oxygen species (ROS), which can cause photodamage. Regulation of photosynthesis is highly dynamic, responding to both environmental and metabolic cues, and occurs at many levels, from light capture to energy storage and metabolic processes. One general mechanism of regulation involves the reversible oxidation and reduction of protein thiol groups, which can affect the activity of enzymes and the stability of proteins. Such redox regulation has been well studied in stromal enzymes, but more recently, evidence has emerged of redox control of thylakoid lumenal enzymes. This review/hypothesis paper summarizes the latest research and discusses several open questions and challenges to achieving effective redox control in the lumen, focusing on the distinct environments and regulatory components of the thylakoid lumen, including the need to transport electrons across the thylakoid membrane, the effects of pH changes by the proton motive force (pmf) in the stromal and lumenal compartments, and the observed differences in redox states. These constraints suggest that activated oxygen species are likely to be major regulatory contributors to lumenal thiol redox regulation, with key components and processes yet to be discovered.
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Affiliation(s)
- Donghee Hoh
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan, USA
| | - John E Froehlich
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan, USA
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, USA
| | - David M Kramer
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan, USA
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, USA
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The ferredoxin/thioredoxin pathway constitutes an indispensable redox-signaling cascade for light-dependent reduction of chloroplast stromal proteins. J Biol Chem 2022; 298:102650. [PMID: 36448836 PMCID: PMC9712825 DOI: 10.1016/j.jbc.2022.102650] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2022] [Revised: 10/18/2022] [Accepted: 10/20/2022] [Indexed: 12/02/2022] Open
Abstract
To ensure efficient photosynthesis, chloroplast proteins need to be flexibly regulated under fluctuating light conditions. Thiol-based redox regulation plays a key role in reductively activating several chloroplast proteins in a light-dependent manner. The ferredoxin (Fd)/thioredoxin (Trx) pathway has long been recognized as the machinery that transfers reducing power generated by photosynthetic electron transport reactions to redox-sensitive target proteins; however, its biological importance remains unclear, because the complete disruption of the Fd/Trx pathway in plants has been unsuccessful to date. Especially, recent identifications of multiple redox-related factors in chloroplasts, as represented by the NADPH-Trx reductase C, have raised a controversial proposal that other redox pathways work redundantly with the Fd/Trx pathway. To address these issues directly, we used CRISPR/Cas9 gene editing to create Arabidopsis mutant plants in which the activity of the Fd/Trx pathway was completely defective. The mutants generated showed severe growth inhibition. Importantly, these mutants almost entirely lost the ability to reduce several redox-sensitive proteins in chloroplast stroma, including four Calvin-Benson cycle enzymes, NADP-malate dehydrogenase, and Rubisco activase, under light conditions. These striking phenotypes were further accompanied by abnormally developed chloroplasts and a drastic decline in photosynthetic efficiency. These results indicate that the Fd/Trx pathway is indispensable for the light-responsive activation of diverse stromal proteins and photoautotrophic growth of plants. Our data also suggest that the ATP synthase is exceptionally reduced by other pathways in a redundant manner. This study provides an important insight into how the chloroplast redox-regulatory system operates in vivo.
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García-Cañas R, Florencio FJ, López-Maury L. Back to the future: Transplanting the chloroplast TrxF-FBPase-SBPase redox system to cyanobacteria. FRONTIERS IN PLANT SCIENCE 2022; 13:1052019. [PMID: 36518499 PMCID: PMC9742560 DOI: 10.3389/fpls.2022.1052019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Accepted: 10/31/2022] [Indexed: 06/17/2023]
Abstract
Fructose-1,6-bisphosphatase (FBPase) and sedoheptulose-1,7-bisphosphatase (SBPase) are two essential activities in the Calvin-Benson-Bassham cycle that catalyze two irreversible reactions and are key for proper regulation and functioning of the cycle. These two activities are codified by a single gene in all cyanobacteria, although some cyanobacteria contain an additional gene coding for a FBPase. Mutants lacking the gene coding for SBP/FBPase protein are not able to grow photoautotrophically and require glucose to survive. As this protein presents both activities, we have tried to elucidate which of the two are required for photoautrophic growth in Synechocystis sp PCC 6803. For this, the genes coding for plant FBPase and SBPase were introduced in a SBP/FBPase mutant strain, and the strains were tested for growth in the absence of glucose. Ectopic expression of only a plant SBPase gene did not allow growth in the absence of glucose although allowed mutation of both Synechocystis' FBPase genes. When both plant FBPase and SBPase genes were expressed, photoautrophic growth of the SBP/FBPase mutants was restored. This complementation was partial as the strain only grew in low light, but growth was impaired at higher light intensities. Redox regulation of the Calvin-Benson-Bassham cycle is essential to properly coordinate light reactions to carbon fixation in the chloroplast. Two of the best characterized proteins that are redox-regulated in the cycle are FBPase and SBPase. These two proteins are targets of the FTR-Trx redox system with Trx f being the main reductant in vivo. Introduction of the TrxF gene improves growth of the complemented strain, suggesting that the redox state of the proteins may be the cause of this phenotype. The redox state of the plant proteins was also checked in these strains, and it shows that the cyanobacterial redox system is able to reduce all of them (SBPase, FBPase, and TrxF) in a light-dependent manner. Thus, the TrxF-FBPase-SBPase plant chloroplast system is active in cyanobacteria despite that these organisms do not contain proteins related to them. Furthermore, our system opens the possibility to study specificity of the Trx system in vivo without the complication of the different isoforms present in plants.
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Affiliation(s)
- Raquel García-Cañas
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla- CSIC, Sevilla, Spain
- Departamento de Bioquímica Vegetal y Biología Molecular, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
| | - Francisco J. Florencio
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla- CSIC, Sevilla, Spain
- Departamento de Bioquímica Vegetal y Biología Molecular, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
| | - Luis López-Maury
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla- CSIC, Sevilla, Spain
- Departamento de Bioquímica Vegetal y Biología Molecular, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
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Riaz A, Deng F, Chen G, Jiang W, Zheng Q, Riaz B, Mak M, Zeng F, Chen ZH. Molecular Regulation and Evolution of Redox Homeostasis in Photosynthetic Machinery. Antioxidants (Basel) 2022; 11:antiox11112085. [PMID: 36358456 PMCID: PMC9686623 DOI: 10.3390/antiox11112085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 10/14/2022] [Accepted: 10/20/2022] [Indexed: 01/14/2023] Open
Abstract
The recent advances in plant biology have significantly improved our understanding of reactive oxygen species (ROS) as signaling molecules in the redox regulation of complex cellular processes. In plants, free radicals and non-radicals are prevalent intra- and inter-cellular ROS, catalyzing complex metabolic processes such as photosynthesis. Photosynthesis homeostasis is maintained by thiol-based systems and antioxidative enzymes, which belong to some of the evolutionarily conserved protein families. The molecular and biological functions of redox regulation in photosynthesis are usually to balance the electron transport chain, photosystem II, photosystem I, mesophyll and bundle sheath signaling, and photo-protection regulating plant growth and productivity. Here, we review the recent progress of ROS signaling in photosynthesis. We present a comprehensive comparative bioinformatic analysis of redox regulation in evolutionary distinct photosynthetic cells. Gene expression, phylogenies, sequence alignments, and 3D protein structures in representative algal and plant species revealed conserved key features including functional domains catalyzing oxidation and reduction reactions. We then discuss the antioxidant-related ROS signaling and important pathways for achieving homeostasis of photosynthesis. Finally, we highlight the importance of plant responses to stress cues and genetic manipulation of disturbed redox status for balanced and enhanced photosynthetic efficiency and plant productivity.
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Affiliation(s)
- Adeel Riaz
- Hubei Collaborative Innovation Center for Grain Industry, College of Agriculture, Yangtze University, Jingzhou 414000, China
| | - Fenglin Deng
- Hubei Collaborative Innovation Center for Grain Industry, College of Agriculture, Yangtze University, Jingzhou 414000, China
| | - Guang Chen
- College of Agriculture and Biotechnology, Zhejiang University, Hangzhou 310058, China
| | - Wei Jiang
- Hubei Collaborative Innovation Center for Grain Industry, College of Agriculture, Yangtze University, Jingzhou 414000, China
| | - Qingfeng Zheng
- Hubei Collaborative Innovation Center for Grain Industry, College of Agriculture, Yangtze University, Jingzhou 414000, China
| | - Bisma Riaz
- Department of Biotechnology, University of Okara, Okara, Punjab 56300, Pakistan
| | - Michelle Mak
- School of Science, Western Sydney University, Penrith, NSW 2751, Australia
| | - Fanrong Zeng
- Hubei Collaborative Innovation Center for Grain Industry, College of Agriculture, Yangtze University, Jingzhou 414000, China
- Correspondence: (F.Z.); (Z.-H.C.)
| | - Zhong-Hua Chen
- School of Science, Western Sydney University, Penrith, NSW 2751, Australia
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW 2751, Australia
- Correspondence: (F.Z.); (Z.-H.C.)
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7
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Sekiguchi T, Yoshida K, Wakabayashi KI, Hisabori T. Dissipation of the proton electrochemical gradient in chloroplasts promotes the oxidation of ATP synthase by thioredoxin-like proteins. J Biol Chem 2022; 298:102541. [PMID: 36174673 PMCID: PMC9626944 DOI: 10.1016/j.jbc.2022.102541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 09/15/2022] [Accepted: 09/21/2022] [Indexed: 12/05/2022] Open
Abstract
Chloroplast FoF1-ATP synthase (CFoCF1) uses an electrochemical gradient of protons across the thylakoid membrane (ΔμH+) as an energy source in the ATP synthesis reaction. CFoCF1 activity is regulated by the redox state of a Cys pair on its central axis, that is, the γ subunit (CF1-γ). When the ΔμH+ is formed by the photosynthetic electron transfer chain under light conditions, CF1-γ is reduced by thioredoxin (Trx), and the entire CFoCF1 enzyme is activated. The redox regulation of CFoCF1 is a key mechanism underlying the control of ATP synthesis under light conditions. In contrast, the oxidative deactivation process involving CFoCF1 has not been clarified. In the present study, we analyzed the oxidation of CF1-γ by two physiological oxidants in the chloroplast, namely the proteins Trx-like 2 and atypical Cys-His-rich Trx. Using the thylakoid membrane containing the reduced form of CFoCF1, we were able to assess the CF1-γ oxidation ability of these Trx-like proteins. Our kinetic analysis indicated that these proteins oxidized CF1-γ with a higher efficiency than that achieved by a chemical oxidant and typical chloroplast Trxs. Additionally, the CF1-γ oxidation rate due to Trx-like proteins and the affinity between them were changed markedly when ΔμH+ formation across the thylakoid membrane was manipulated artificially. Collectively, these results indicate that the formation status of the ΔμH+ controls the redox regulation of CFoCF1 to prevent energetic disadvantages in plants.
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Affiliation(s)
- Takatoshi Sekiguchi
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Nagatsuta-cho 4259-R1-8, Midori-Ku, Yokohama 226-8503, Japan; School of Life Science and Technology, Tokyo Institute of Technology, Nagatsuta-cho 4259-R1-8, Midori-ku, Yokohama 226-8503, Japan
| | - Keisuke Yoshida
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Nagatsuta-cho 4259-R1-8, Midori-Ku, Yokohama 226-8503, Japan; School of Life Science and Technology, Tokyo Institute of Technology, Nagatsuta-cho 4259-R1-8, Midori-ku, Yokohama 226-8503, Japan
| | - Ken-Ichi Wakabayashi
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Nagatsuta-cho 4259-R1-8, Midori-Ku, Yokohama 226-8503, Japan; School of Life Science and Technology, Tokyo Institute of Technology, Nagatsuta-cho 4259-R1-8, Midori-ku, Yokohama 226-8503, Japan
| | - Toru Hisabori
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Nagatsuta-cho 4259-R1-8, Midori-Ku, Yokohama 226-8503, Japan; School of Life Science and Technology, Tokyo Institute of Technology, Nagatsuta-cho 4259-R1-8, Midori-ku, Yokohama 226-8503, Japan.
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8
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Verification of the Relationship between Redox Regulation of Thioredoxin Target Proteins and Their Proximity to Thylakoid Membranes. Antioxidants (Basel) 2022; 11:antiox11040773. [PMID: 35453458 PMCID: PMC9032623 DOI: 10.3390/antiox11040773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 04/07/2022] [Accepted: 04/11/2022] [Indexed: 02/04/2023] Open
Abstract
Thioredoxin (Trx) is a key protein of the redox regulation system in chloroplasts, where it modulates various enzyme activities. Upon light irradiation, Trx reduces the disulfide bonds of Trx target proteins (thereby turning on their activities) using reducing equivalents obtained from the photosynthetic electron transport chain. This reduction process involves a differential response, i.e., some Trx target proteins in the stroma respond slowly to the change in redox condition caused by light/dark changes, while the ATP synthase γ subunit (CF1-γ) located on the surface of thylakoid membrane responds with high sensitivity. The factors that determine this difference in redox kinetics are not yet known, although here, we hypothesize that it is due to each protein’s localization in the chloroplast, i.e., the reducing equivalents generated under light conditions can be transferred more efficiently to the proteins on thylakoid membrane than to stromal proteins. To explore this possibility, we anchored SBPase, one of the stromal Trx target proteins, to the thylakoid membrane in Arabidopsis thaliana. Analyses of the redox behaviors of the anchored and unanchored proteins showed no significant difference in their reduction kinetics, implying that protein sensitivity to redox regulation is determined by other factors.
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9
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In vivo oxidation by thioredoxin regulates chloroplast enzyme activity. Proc Natl Acad Sci U S A 2022; 119:2121408119. [PMID: 35115333 PMCID: PMC8851521 DOI: 10.1073/pnas.2121408119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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10
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Oxidative regulation of chloroplast enzymes by thioredoxin and thioredoxin-like proteins in Arabidopsis thaliana. Proc Natl Acad Sci U S A 2021; 118:2114952118. [PMID: 34907017 PMCID: PMC8713810 DOI: 10.1073/pnas.2114952118] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/02/2021] [Indexed: 11/30/2022] Open
Abstract
Plants modulate photosynthesis activity in response to the surrounding environment. It is well known that the redox-responsive protein thioredoxin (Trx) activates photosynthesis-related enzymes in the light. However, the factors involved in deactivating them are not well understood. Recent in vitro experiments suggest that several Trx and Trx-like proteins serve as oxidation factors for Trx-targeted proteins; thus, we examined their functions in vivo. Consequently, we found that f-type Trx and two types of Trx-like proteins, Trx-like 2 and atypical Cys His-rich Trx, were involved in oxidative deactivation of photosynthesis-related enzymes (e.g., fructose-1,6-bisphosphatase, Rubisco activase, and the ATP synthase γ-subunit). Thus, this study reveals the functions of oxidation factors in vivo and elucidates the regulation system for photosynthesis in the dark. Thioredoxin (Trx) is a protein that mediates the reducing power transfer from the photosynthetic electron transport system to target enzymes in chloroplasts and regulates their activities. Redox regulation governed by Trx is a system that is central to the adaptation of various chloroplast functions to the ever-changing light environment. However, the factors involved in the opposite reaction (i.e., the oxidation of various enzymes) have yet to be revealed. Recently, it has been suggested that Trx and Trx-like proteins could oxidize Trx-targeted proteins in vitro. To elucidate the in vivo function of these proteins as oxidation factors, we generated mutant plant lines deficient in Trx or Trx-like proteins and studied how the proteins are involved in oxidative regulation in chloroplasts. We found that f-type Trx and two types of Trx-like proteins, Trx-like 2 and atypical Cys His-rich Trx (ACHT), seemed to serve as oxidation factors for Trx-targeted proteins, such as fructose-1,6-bisphosphatase, Rubisco activase, and the γ-subunit of ATP synthase. In addition, ACHT was found to be involved in regulating nonphotochemical quenching, which is the mechanism underlying the thermal dissipation of excess light energy. Overall, these results indicate that Trx and Trx-like proteins regulate chloroplast functions in concert by controlling the redox state of various photosynthesis-related proteins in vivo.
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11
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Yoshida K, Hisabori T. Biochemical Basis for Redox Regulation of Chloroplast-Localized Phosphofructokinase from Arabidopsis thaliana. PLANT & CELL PHYSIOLOGY 2021; 62:401-410. [PMID: 33416847 DOI: 10.1093/pcp/pcaa174] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Accepted: 12/20/2020] [Indexed: 05/10/2023]
Abstract
Various proteins in plant chloroplasts are subject to thiol-based redox regulation, allowing light-responsive control of chloroplast functions. Most redox-regulated proteins are known to be reductively activated in the light in a thioredoxin (Trx)-dependent manner, but its regulatory network remains incompletely understood. Using a biochemical procedure, we here show that a specific form of phosphofructokinase (PFK) is a novel redox-regulated protein whose activity is suppressed upon reduction. PFK is a key enzyme in the glycolytic pathway. In Arabidopsis thaliana, PFK5 is targeted to chloroplasts and uniquely contains an insertion sequence harboring two Cys residues (Cys152 and Cys157) in the N-terminal region. Redox shift assays using a thiol-modifying reagent indicated that PFK5 is efficiently reduced by a specific type of Trx, namely, Trx-f. PFK5 enzyme activity was lowered with the Trx-f-dependent reduction. PFK5 redox regulation was bidirectional; PFK5 was also oxidized and activated by the recently identified Trx-like2/2-Cys peroxiredoxin pathway. Mass spectrometry-based peptide mapping analysis revealed that Cys152 and Cys157 are critical for the intramolecular disulfide bond formation in PFK5. The involvement of Cys152 and Cys157 in PFK5 redox regulation was further supported by a site-directed mutagenesis study. PFK5 catalyzes the reverse reaction of fructose 1,6-bisphosphatase (FBPase), which is reduced and activated specifically by Trx-f. Our data suggest that PFK5 redox regulation, together with that of FBPase, constitutes a checkpoint for switching light/dark metabolism in chloroplasts.
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Affiliation(s)
- Keisuke Yoshida
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Nagatsuta-cho 4259-R1-8, Midori-ku, Yokohama, 226-8503 Japan
| | - Toru Hisabori
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Nagatsuta-cho 4259-R1-8, Midori-ku, Yokohama, 226-8503 Japan
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12
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Le Moigne T, Gurrieri L, Crozet P, Marchand CH, Zaffagnini M, Sparla F, Lemaire SD, Henri J. Crystal structure of chloroplastic thioredoxin z defines a type-specific target recognition. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 107:434-447. [PMID: 33930214 DOI: 10.1111/tpj.15300] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 04/13/2021] [Accepted: 04/22/2021] [Indexed: 06/12/2023]
Abstract
Thioredoxins (TRXs) are ubiquitous disulfide oxidoreductases structured according to a highly conserved fold. TRXs are involved in a myriad of different processes through a common chemical mechanism. Plant TRXs evolved into seven types with diverse subcellular localization and distinct protein target selectivity. Five TRX types coexist in the chloroplast, with yet scarcely described specificities. We solved the crystal structure of a chloroplastic z-type TRX, revealing a conserved TRX fold with an original electrostatic surface potential surrounding the redox site. This recognition surface is distinct from all other known TRX types from plant and non-plant sources and is exclusively conserved in plant z-type TRXs. We show that this electronegative surface endows thioredoxin z (TRXz) with a capacity to activate the photosynthetic Calvin-Benson cycle enzyme phosphoribulokinase. The distinct electronegative surface of TRXz thereby extends the repertoire of TRX-target recognitions.
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Affiliation(s)
- Théo Le Moigne
- Laboratoire de Biologie Computationnelle et Quantitative, Institut de Biologie Paris-Seine, UMR 7238, CNRS, Sorbonne Université, 4 Place Jussieu, Paris, 75005, France
- Faculty of Sciences, Doctoral School of Plant Sciences, Université Paris-Saclay, Saint-Aubin, 91190, France
- Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, UMR 8226, CNRS, Sorbonne Université, 13 Rue Pierre et Marie Curie, Paris, 75005, France
| | - Libero Gurrieri
- Department of Pharmacy and Biotechnology, University of Bologna, Via Irnerio 42, Bologna, 40126, Italy
| | - Pierre Crozet
- Laboratoire de Biologie Computationnelle et Quantitative, Institut de Biologie Paris-Seine, UMR 7238, CNRS, Sorbonne Université, 4 Place Jussieu, Paris, 75005, France
- Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, UMR 8226, CNRS, Sorbonne Université, 13 Rue Pierre et Marie Curie, Paris, 75005, France
- Sorbonne Université, Polytech Sorbonne, Paris, 75005, France
| | - Christophe H Marchand
- Laboratoire de Biologie Computationnelle et Quantitative, Institut de Biologie Paris-Seine, UMR 7238, CNRS, Sorbonne Université, 4 Place Jussieu, Paris, 75005, France
- Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, UMR 8226, CNRS, Sorbonne Université, 13 Rue Pierre et Marie Curie, Paris, 75005, France
- Plateforme de Protéomique, Institut de Biologie Physico-Chimique, FR 550, CNRS, 13 Rue Pierre et Marie Curie, Paris, 75005, France
| | - Mirko Zaffagnini
- Department of Pharmacy and Biotechnology, University of Bologna, Via Irnerio 42, Bologna, 40126, Italy
| | - Francesca Sparla
- Department of Pharmacy and Biotechnology, University of Bologna, Via Irnerio 42, Bologna, 40126, Italy
| | - Stéphane D Lemaire
- Laboratoire de Biologie Computationnelle et Quantitative, Institut de Biologie Paris-Seine, UMR 7238, CNRS, Sorbonne Université, 4 Place Jussieu, Paris, 75005, France
- Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, UMR 8226, CNRS, Sorbonne Université, 13 Rue Pierre et Marie Curie, Paris, 75005, France
| | - Julien Henri
- Laboratoire de Biologie Computationnelle et Quantitative, Institut de Biologie Paris-Seine, UMR 7238, CNRS, Sorbonne Université, 4 Place Jussieu, Paris, 75005, France
- Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes, Institut de Biologie Physico-Chimique, UMR 8226, CNRS, Sorbonne Université, 13 Rue Pierre et Marie Curie, Paris, 75005, France
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13
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Yokochi Y, Yoshida K, Hahn F, Miyagi A, Wakabayashi KI, Kawai-Yamada M, Weber APM, Hisabori T. Redox regulation of NADP-malate dehydrogenase is vital for land plants under fluctuating light environment. Proc Natl Acad Sci U S A 2021; 118:e2016903118. [PMID: 33531363 PMCID: PMC8017969 DOI: 10.1073/pnas.2016903118] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Many enzymes involved in photosynthesis possess highly conserved cysteine residues that serve as redox switches in chloroplasts. These redox switches function to activate or deactivate enzymes during light-dark transitions and have the function of fine-tuning their activities according to the intensity of light. Accordingly, many studies on chloroplast redox regulation have been conducted under the hypothesis that "fine regulation of the activities of these enzymes is crucial for efficient photosynthesis." However, the impact of the regulatory system on plant metabolism is still unclear. To test this hypothesis, we here studied the impact of the ablation of a redox switch in chloroplast NADP-malate dehydrogenase (MDH). By genome editing, we generated a mutant plant whose MDH lacks one of its redox switches and is active even in dark conditions. Although NADPH consumption by MDH in the dark is expected to be harmful to plant growth, the mutant line did not show any phenotypic differences under standard long-day conditions. In contrast, the mutant line showed severe growth retardation under short-day or fluctuating light conditions. These results indicate that thiol-switch redox regulation of MDH activity is crucial for maintaining NADPH homeostasis in chloroplasts under these conditions.
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Affiliation(s)
- Yuichi Yokochi
- Laboratory of Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, 226-8503 Yokohama, Japan
- School of Life Science and Technology, Tokyo Institute of Technology, 226-8503 Yokohama, Japan
| | - Keisuke Yoshida
- Laboratory of Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, 226-8503 Yokohama, Japan
- School of Life Science and Technology, Tokyo Institute of Technology, 226-8503 Yokohama, Japan
| | - Florian Hahn
- Institute of Plant Biochemistry, Cluster of Excellence on Plant Sciences, Center for Synthetic Life Sciences, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Atsuko Miyagi
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 338-8570 Saitama, Japan
| | - Ken-Ichi Wakabayashi
- Laboratory of Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, 226-8503 Yokohama, Japan
- School of Life Science and Technology, Tokyo Institute of Technology, 226-8503 Yokohama, Japan
| | - Maki Kawai-Yamada
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 338-8570 Saitama, Japan
| | - Andreas P M Weber
- Institute of Plant Biochemistry, Cluster of Excellence on Plant Sciences, Center for Synthetic Life Sciences, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| | - Toru Hisabori
- Laboratory of Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, 226-8503 Yokohama, Japan;
- School of Life Science and Technology, Tokyo Institute of Technology, 226-8503 Yokohama, Japan
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14
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Ji H, Liu D, Zhang Z, Sun J, Han B, Li Z. A bacterial F-box effector suppresses SAR immunity through mediating the proteasomal degradation of OsTrxh2 in rice. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 104:1054-1072. [PMID: 32881160 DOI: 10.1111/tpj.14980] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 08/06/2020] [Accepted: 08/10/2020] [Indexed: 06/11/2023]
Abstract
Plant bacterial pathogens usually cause diseases by secreting and translocating numerous virulence effectors into host cells and suppressing various host immunity pathways. It has been demonstrated that the extensive ubiquitin systems of host cells are frequently interfered with or hijacked by numerous pathogenic bacteria, through various strategies. Some type-III secretion system (T3SS) effectors of plant pathogens have been demonstrated to impersonate the F-box protein (FBP) component of the SKP1/CUL1/F-box (SCF) E3 ubiquitin system for their own benefit. Although numerous putative eukaryotic-like F-box effectors have been screened for different bacterial pathogens by bioinformatics analyses, the targets of most F-box effectors in host immune systems remain unknown. Here, we show that XopI, a putative F-box effector of African Xoo (Xanthomonas oryzae pv. oryzae) strain BAI3, strongly inhibits the host's OsNPR1-dependent resistance to Xoo. The xopI knockout mutant displays lower virulence in Oryza sativa (rice) than BAI3. Mechanistically, we identify a thioredoxin protein, OsTrxh2, as an XopI-interacting protein in rice. Although OsTrxh2 positively regulates rice immunity by catalyzing the dissociation of OsNPR1 into monomers in rice, the XopI effector serves as an F-box adapter to form an OSK1-XopI-OsTrxh2 interaction complex, and further disrupts OsNPR1-mediated resistance through proteasomal degradation of OsTrxh2. Our results indicate that XopI targets OsTrxh2 and further represses OsNPR1-dependent signaling, thereby subverting systemic acquired resistance (SAR) immunity in rice.
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Affiliation(s)
- Hongtao Ji
- Institute of Integrative Plant Biology, School of Life Sciences, Jiangsu Normal University, Xuzhou, 221116, China
| | - Delong Liu
- Institute of Integrative Plant Biology, School of Life Sciences, Jiangsu Normal University, Xuzhou, 221116, China
| | - Zhaoxin Zhang
- The State Key Laboratory of Pharmaceutical Biotechnology, School of life Sciences, Nanjing University, Nanjing, 210023, China
| | - Jiawen Sun
- Institute of Integrative Plant Biology, School of Life Sciences, Jiangsu Normal University, Xuzhou, 221116, China
| | - Bing Han
- Institute of Plant Protection, Dezhou Academy of Agricultural Sciences, Dezhou, 253015, China
| | - Zongyun Li
- Institute of Integrative Plant Biology, School of Life Sciences, Jiangsu Normal University, Xuzhou, 221116, China
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15
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Yoshida K, Ohtaka K, Hirai MY, Hisabori T. Biochemical insight into redox regulation of plastidial 3-phosphoglycerate dehydrogenase from Arabidopsis thaliana. J Biol Chem 2020; 295:14906-14915. [PMID: 32848019 PMCID: PMC7606689 DOI: 10.1074/jbc.ra120.014263] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 08/22/2020] [Indexed: 12/22/2022] Open
Abstract
Thiol-based redox regulation is a post-translational protein modification for controlling enzyme activity by switching oxidation/reduction states of Cys residues. In plant cells, numerous proteins involved in a wide range of biological systems have been suggested as the target of redox regulation; however, our knowledge on this issue is still incomplete. Here we report that 3-phosphoglycerate dehydrogenase (PGDH) is a novel redox-regulated protein. PGDH catalyzes the first committed step of Ser biosynthetic pathway in plastids. Using an affinity chromatography-based method, we found that PGDH physically interacts with thioredoxin (Trx), a key factor of redox regulation. The in vitro studies using recombinant proteins from Arabidopsis thaliana showed that a specific PGDH isoform, PGDH1, forms the intramolecular disulfide bond under nonreducing conditions, which lowers PGDH enzyme activity. MS and site-directed mutagenesis analyses allowed us to identify the redox-active Cys pair that is mainly involved in disulfide bond formation in PGDH1; this Cys pair is uniquely found in land plant PGDH. Furthermore, we revealed that some plastidial Trx subtypes support the reductive activation of PGDH1. The present data show previously uncharacterized regulatory mechanisms of PGDH and expand our understanding of the Trx-mediated redox-regulatory network in plants.
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Affiliation(s)
- Keisuke Yoshida
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan.
| | - Kinuka Ohtaka
- RIKEN Center for Sustainable Resource Science, Yokohama, Japan; Department of Chemical and Biological Sciences, Faculty of Science, Japan Women's University, Tokyo, Japan
| | | | - Toru Hisabori
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan.
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16
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Sytykiewicz H, Łukasik I, Goławska S, Sprawka I, Goławski A, Sławianowska J, Kmieć K. Expression of Thioredoxin/Thioredoxin Reductase System Genes in Aphid-Challenged Maize Seedlings. Int J Mol Sci 2020; 21:ijms21176296. [PMID: 32878074 PMCID: PMC7503728 DOI: 10.3390/ijms21176296] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 08/27/2020] [Accepted: 08/29/2020] [Indexed: 11/16/2022] Open
Abstract
Thioredoxins (Trxs) and thioredoxin reductases (TrxRs) encompass a highly complex network involved in sustaining thiol-based redox homeostasis in plant tissues. The purpose of the study was to gain a new insight into transcriptional reprogramming of the several genes involved in functioning of Trx/TrxR system in maize (Zea mays L.) seedlings, exposed to the bird cherry-oat aphid (Rhopalosiphum padi L.) or the rose-grass aphid (Metopolophium dirhodum Walk.) infestation. The biotests were performed on two maize genotypes (susceptible Złota Karłowa and relatively resistant Waza). The application of real-time qRT-PCR technique allowed to identify a molecular mechanism triggered in more resistant maize plants, linked to upregulation of thioredoxins-encoding genes (Trx-f, Trx-h, Trx-m, Trx-x) and thioredoxin reductase genes (Ftr1, Trxr2). Significant enhancement of TrxR activity in aphid-infested Waza seedlings was also demonstrated. Furthermore, we used an electrical penetration graph (EPG) recordings of M. dirhodum stylet activities in seedlings of the two studied maize varieties. Duration of phloem phase (E1 and E2 models) of rose-grass aphids was about three times longer while feeding in Waza plants, compared to Złota Karłowa cv. The role of activation of Trx/TrxR system in maintaining redox balance and counteracting oxidative-induced damages of macromolecules in aphid-stressed maize plants is discussed.
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Affiliation(s)
- Hubert Sytykiewicz
- Institute of Biological Sciences, Faculty of Exact and Natural Sciences, Siedlce University of Natural Sciences and Humanities, 14 Prusa St., 08-110 Siedlce, Poland; (I.Ł.); (S.G.); (I.S.); (A.G.); (J.S.)
- Correspondence: ; Tel.: +48-25-643-12-98
| | - Iwona Łukasik
- Institute of Biological Sciences, Faculty of Exact and Natural Sciences, Siedlce University of Natural Sciences and Humanities, 14 Prusa St., 08-110 Siedlce, Poland; (I.Ł.); (S.G.); (I.S.); (A.G.); (J.S.)
| | - Sylwia Goławska
- Institute of Biological Sciences, Faculty of Exact and Natural Sciences, Siedlce University of Natural Sciences and Humanities, 14 Prusa St., 08-110 Siedlce, Poland; (I.Ł.); (S.G.); (I.S.); (A.G.); (J.S.)
| | - Iwona Sprawka
- Institute of Biological Sciences, Faculty of Exact and Natural Sciences, Siedlce University of Natural Sciences and Humanities, 14 Prusa St., 08-110 Siedlce, Poland; (I.Ł.); (S.G.); (I.S.); (A.G.); (J.S.)
| | - Artur Goławski
- Institute of Biological Sciences, Faculty of Exact and Natural Sciences, Siedlce University of Natural Sciences and Humanities, 14 Prusa St., 08-110 Siedlce, Poland; (I.Ł.); (S.G.); (I.S.); (A.G.); (J.S.)
| | - Julia Sławianowska
- Institute of Biological Sciences, Faculty of Exact and Natural Sciences, Siedlce University of Natural Sciences and Humanities, 14 Prusa St., 08-110 Siedlce, Poland; (I.Ł.); (S.G.); (I.S.); (A.G.); (J.S.)
| | - Katarzyna Kmieć
- Department of Plant Protection, Faculty of Horticulture and Landscape Architecture, University of Life Sciences in Lublin, 7 Leszczyńskiego St., 20-069 Lublin, Poland;
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17
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Regulatory thiol oxidation in chloroplast metabolism, oxidative stress response and environmental signaling in plants. Biochem J 2020; 477:1865-1878. [DOI: 10.1042/bcj20190124] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Revised: 05/04/2020] [Accepted: 05/05/2020] [Indexed: 12/28/2022]
Abstract
The antagonism between thiol oxidation and reduction enables efficient control of protein function and is used as central mechanism in cellular regulation. The best-studied mechanism is the dithiol-disulfide transition in the Calvin Benson Cycle in photosynthesis, including mixed disulfide formation by glutathionylation. The adjustment of the proper thiol redox state is a fundamental property of all cellular compartments. The glutathione redox potential of the cytosol, stroma, matrix and nucleoplasm usually ranges between −300 and −320 mV. Thiol reduction proceeds by short electron transfer cascades consisting of redox input elements and redox transmitters such as thioredoxins. Thiol oxidation ultimately is linked to reactive oxygen species (ROS) and reactive nitrogen species (RNS). Enhanced ROS production under stress shifts the redox network to more positive redox potentials. ROS do not react randomly but primarily with few specific redox sensors in the cell. The most commonly encountered reaction within the redox regulatory network however is the disulfide swapping. The thiol oxidation dynamics also involves transnitrosylation. This review compiles present knowledge on this network and its central role in sensing environmental cues with focus on chloroplast metabolism.
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18
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Yoshida K, Yokochi Y, Hisabori T. New Light on Chloroplast Redox Regulation: Molecular Mechanism of Protein Thiol Oxidation. FRONTIERS IN PLANT SCIENCE 2019; 10:1534. [PMID: 31824547 PMCID: PMC6882916 DOI: 10.3389/fpls.2019.01534] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 11/01/2019] [Indexed: 05/21/2023]
Abstract
Thiol-based redox regulation is a posttranslational protein modification that plays a key role in adjusting chloroplast functions in response to changing light conditions. Redox-sensitive target proteins are reduced upon illumination, which turns on (or off in a certain case) their enzyme activities. A redox cascade via ferredoxin, ferredoxin-thioredoxin reductase, and thioredoxin has been classically recognized as the key system for transmitting the light-induced reductive signal to target proteins. By contrast, the molecular mechanism underlying target protein oxidation, which is observed during light to dark transitions, remains undetermined over the past several decades. Recently, the factors and pathways for protein thiol oxidation in chloroplasts have been reported, finally shedding light on this long-standing issue. We identified thioredoxin-like2 as one of the protein-oxidation factors in chloroplasts. This protein is characterized by its higher redox potential than that of canonical thioredoxin, that is more favorable for target protein oxidation. Furthermore, 2-Cys peroxiredoxin and hydrogen peroxide are also involved in the overall protein-oxidation machinery. Here we summarize the newly uncovered "dark side" of chloroplast redox regulation, giving an insight into how plants rest their photosynthetic activity at night.
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Affiliation(s)
- Keisuke Yoshida
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan
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