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Kobayashi R, Yamamoto H, Ishibashi K, Shikanai T. Critical role of cyclic electron transport around photosystem I in the maintenance of photosystem I activity. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2024; 118:2141-2153. [PMID: 38558422 DOI: 10.1111/tpj.16735] [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: 09/19/2023] [Revised: 03/05/2024] [Accepted: 03/14/2024] [Indexed: 04/04/2024]
Abstract
In angiosperms, cyclic electron transport around photosystem I (PSI) is mediated by two pathways that depend on the PROTON GRADIENT REGULATION 5 (PGR5) protein and the chloroplast NADH dehydrogenase-like (NDH) complex, respectively. In the Arabidopsis double mutants defective in both pathways, plant growth and photosynthesis are impaired. The pgr5-1 mutant used in the original study is a missense allele and accumulates low levels of PGR5 protein. In this study, we generated two knockout (KO) alleles, designated as pgr5-5 and pgr5-6, using the CRISPR-Cas9 technology. Although both KO alleles showed a severe reduction in P700 similar to the pgr5-1 allele, NPQ induction was less severely impaired in the KO alleles than in the pgr5-1 allele. In the pgr5-1 allele, the second mutation affecting NPQ size was mapped to ~21 cM south of the pgr5-1 locus. Overexpression of the pgr5-1 allele, encoding the glycine130-to-serine change, complemented the pgr5-5 phenotype, suggesting that the pgr5-1 mutation destabilizes PGR5 but that the mutant protein retains partial functionality. Using two KO alleles, we created the double mutants with two chlororespiratory reduction (crr) mutants defective in the NDH complex. The growth of the double mutants was notably impaired. In the double mutant seedlings that survived on the medium containing sucrose, PSI activity evaluated by the P700 oxidation was severely impaired, whereas PSII activity was only mildly impaired. Cyclic electron transport around PSI is required to maintain PSI activity.
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Affiliation(s)
- Ryouhei Kobayashi
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
| | - Hiroshi Yamamoto
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
| | - Kota Ishibashi
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
| | - Toshiharu Shikanai
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
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2
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Shikanai T. Molecular Genetic Dissection of the Regulatory Network of Proton Motive Force in Chloroplasts. PLANT & CELL PHYSIOLOGY 2024; 65:537-550. [PMID: 38150384 DOI: 10.1093/pcp/pcad157] [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: 10/16/2023] [Revised: 11/27/2023] [Accepted: 12/08/2023] [Indexed: 12/29/2023]
Abstract
The proton motive force (pmf) generated across the thylakoid membrane rotates the Fo-ring of ATP synthase in chloroplasts. The pmf comprises two components: membrane potential (∆Ψ) and proton concentration gradient (∆pH). Acidification of the thylakoid lumen resulting from ∆pH downregulates electron transport in the cytochrome b6f complex. This process, known as photosynthetic control, is crucial for protecting photosystem I (PSI) from photodamage in response to fluctuating light. To optimize the balance between efficient photosynthesis and photoprotection, it is necessary to regulate pmf. Cyclic electron transport around PSI and pseudo-cyclic electron transport involving flavodiiron proteins contribute to the modulation of pmf magnitude. By manipulating the ratio between the two components of pmf, it is possible to modify the extent of photosynthetic control without affecting the pmf size. This adjustment can be achieved by regulating the movement of ions (such as K+ and Cl-) across the thylakoid membrane. Since ATP synthase is the primary consumer of pmf in chloroplasts, its activity must be precisely regulated to accommodate other mechanisms involved in pmf optimization. Although fragments of information about each regulatory process have been accumulated, a comprehensive understanding of their interactions is lacking. Here, I summarize current knowledge of the network for pmf regulation, mainly based on genetic studies.
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Affiliation(s)
- Toshiharu Shikanai
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto, 606-8502 Japan
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3
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Penzler JF, Naranjo B, Walz S, Marino G, Kleine T, Leister D. A pgr5 suppressor screen uncovers two distinct suppression mechanisms and links cytochrome b6f complex stability to PGR5. THE PLANT CELL 2024:koae098. [PMID: 38781425 DOI: 10.1093/plcell/koae098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Accepted: 03/13/2024] [Indexed: 05/25/2024]
Abstract
PROTON GRADIENT REGULATION5 (PGR5) is thought to promote cyclic electron flow, and its deficiency impairs photosynthetic control and increases photosensitivity of photosystem (PS) I, leading to seedling lethality under fluctuating light (FL). By screening for Arabidopsis (Arabidopsis thaliana) suppressor mutations that rescue the seedling lethality of pgr5 plants under FL, we identified a portfolio of mutations in 12 different genes. These mutations affect either PSII function, cytochrome b6f (cyt b6f) assembly, plastocyanin (PC) accumulation, the CHLOROPLAST FRUCTOSE-1,6-BISPHOSPHATASE1 (cFBP1), or its negative regulator ATYPICAL CYS HIS-RICH THIOREDOXIN2 (ACHT2). The characterization of the mutants indicates that the recovery of viability can in most cases be explained by the restoration of PSI donor side limitation, which is caused by reduced electron flow to PSI due to defects in PSII, cyt b6f, or PC. Inactivation of cFBP1 or its negative regulator ACHT2 results in increased levels of the NADH dehydrogenase-like complex. This increased activity may be responsible for suppressing the pgr5 phenotype under FL conditions. Plants that lack both PGR5 and DE-ETIOLATION-INDUCED PROTEIN1 (DEIP1)/NEW TINY ALBINO1 (NTA1), previously thought to be essential for cyt b6f assembly, are viable and accumulate cyt b6f. We suggest that PGR5 can have a negative effect on the cyt b6f complex and that DEIP1/NTA1 can ameliorate this negative effect.
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Affiliation(s)
- Jan-Ferdinand Penzler
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Planegg-Martinsried D-82152, Germany
| | - Belén Naranjo
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Planegg-Martinsried D-82152, Germany
| | - Sabrina Walz
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Planegg-Martinsried D-82152, Germany
| | - Giada Marino
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Planegg-Martinsried D-82152, Germany
| | - Tatjana Kleine
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Planegg-Martinsried D-82152, Germany
| | - Dario Leister
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, Planegg-Martinsried D-82152, Germany
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4
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Tikhonov AN. The cytochrome b 6f complex: plastoquinol oxidation and regulation of electron transport in chloroplasts. PHOTOSYNTHESIS RESEARCH 2024; 159:203-227. [PMID: 37369875 DOI: 10.1007/s11120-023-01034-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Accepted: 06/12/2023] [Indexed: 06/29/2023]
Abstract
In oxygenic photosynthetic systems, the cytochrome b6f (Cytb6f) complex (plastoquinol:plastocyanin oxidoreductase) is a heart of the hub that provides connectivity between photosystems (PS) II and I. In this review, the structure and function of the Cytb6f complex are briefly outlined, being focused on the mechanisms of a bifurcated (two-electron) oxidation of plastoquinol (PQH2). In plant chloroplasts, under a wide range of experimental conditions (pH and temperature), a diffusion of PQH2 from PSII to the Cytb6f does not limit the intersystem electron transport. The overall rate of PQH2 turnover is determined mainly by the first step of the bifurcated oxidation of PQH2 at the catalytic site Qo, i.e., the reaction of electron transfer from PQH2 to the Fe2S2 cluster of the high-potential Rieske iron-sulfur protein (ISP). This point has been supported by the quantum chemical analysis of PQH2 oxidation within the framework of a model system including the Fe2S2 cluster of the ISP and surrounding amino acids, the low-potential heme b6L, Glu78 and 2,3,5-trimethylbenzoquinol (the tail-less analog of PQH2). Other structure-function relationships and mechanisms of electron transport regulation of oxygenic photosynthesis associated with the Cytb6f complex are briefly outlined: pH-dependent control of the intersystem electron transport and the regulatory balance between the operation of linear and cyclic electron transfer chains.
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Affiliation(s)
- Alexander N Tikhonov
- Department of Biophysics, Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow, Russian Federation, 119991.
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5
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Ozawa SI, Zhang G, Sakamoto W. Dysfunction of Chloroplast Protease Activity Mitigates pgr5 Phenotype in the Green Algae Chlamydomonas reinhardtii. PLANTS (BASEL, SWITZERLAND) 2024; 13:606. [PMID: 38475453 DOI: 10.3390/plants13050606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Revised: 02/16/2024] [Accepted: 02/18/2024] [Indexed: 03/14/2024]
Abstract
Researchers have described protection mechanisms against the photoinhibition of photosystems under strong-light stress. Cyclic Electron Flow (CEF) mitigates electron acceptor-side limitation, and thus contributes to Photosystem I (PSI) protection. Chloroplast protease removes damaged protein to assist with protein turn over, which contributes to the quality control of Photosystem II (PSII). The PGR5 protein is involved in PGR5-dependent CEF. The FTSH protein is a chloroplast protease which effectively degrades the damaged PSII reaction center subunit, D1 protein. To investigate how the PSI photoinhibition phenotype in pgr5 would be affected by adding the ftsh mutation, we generated double-mutant pgr5ftsh via crossing, and its phenotype was characterized in the green algae Chlamydomonas reinhardtii. The cells underwent high-light incubation as well as low-light incubation after high-light incubation. The time course of Fv/Fm values in pgr5ftsh showed the same phenotype with ftsh1-1. The amplitude of light-induced P700 photo-oxidation absorbance change was measured. The amplitude was maintained at a low value in the control and pgr5ftsh during high-light incubation, but was continuously decreased in pgr5. During the low-light incubation after high-light incubation, amplitude was more rapidly recovered in pgr5ftsh than pgr5. We concluded that the PSI photoinhibition by the pgr5 mutation is mitigated by an additional ftsh1-1 mutation, in which plastoquinone pool would be less reduced due to damaged PSII accumulation.
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Affiliation(s)
- Shin-Ichiro Ozawa
- Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan
| | - Guoxian Zhang
- College of Land and Environment, Shenyang Agricultural University, Shenyang 110866, China
| | - Wataru Sakamoto
- Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan
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Hehenberger E, Guo J, Wilken S, Hoadley K, Sudek L, Poirier C, Dannebaum R, Susko E, Worden AZ. Phosphate Limitation Responses in Marine Green Algae Are Linked to Reprogramming of the tRNA Epitranscriptome and Codon Usage Bias. Mol Biol Evol 2023; 40:msad251. [PMID: 37987557 PMCID: PMC10735309 DOI: 10.1093/molbev/msad251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 11/14/2023] [Accepted: 11/16/2023] [Indexed: 11/22/2023] Open
Abstract
Marine algae are central to global carbon fixation, and their productivity is dictated largely by resource availability. Reduced nutrient availability is predicted for vast oceanic regions as an outcome of climate change; however, there is much to learn regarding response mechanisms of the tiny picoplankton that thrive in these environments, especially eukaryotic phytoplankton. Here, we investigate responses of the picoeukaryote Micromonas commoda, a green alga found throughout subtropical and tropical oceans. Under shifting phosphate availability scenarios, transcriptomic analyses revealed altered expression of transfer RNA modification enzymes and biased codon usage of transcripts more abundant during phosphate-limiting versus phosphate-replete conditions, consistent with the role of transfer RNA modifications in regulating codon recognition. To associate the observed shift in the expression of the transfer RNA modification enzyme complement with the transfer RNAs encoded by M. commoda, we also determined the transfer RNA repertoire of this alga revealing potential targets of the modification enzymes. Codon usage bias was particularly pronounced in transcripts encoding proteins with direct roles in managing phosphate limitation and photosystem-associated proteins that have ill-characterized putative functions in "light stress." The observed codon usage bias corresponds to a proposed stress response mechanism in which the interplay between stress-induced changes in transfer RNA modifications and skewed codon usage in certain essential response genes drives preferential translation of the encoded proteins. Collectively, we expose a potential underlying mechanism for achieving growth under enhanced nutrient limitation that extends beyond the catalog of up- or downregulated protein-encoding genes to the cell biological controls that underpin acclimation to changing environmental conditions.
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Affiliation(s)
- Elisabeth Hehenberger
- Ocean EcoSystems Biology Unit, RD3, GEOMAR Helmholtz Centre for Ocean Research, 24148 Kiel, DE
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, 370 05 České Budějovice, CZ
| | - Jian Guo
- Ocean Sciences Department, University of California Santa Cruz, Santa Cruz, CA 95064, USA
| | - Susanne Wilken
- Ocean Sciences Department, University of California Santa Cruz, Santa Cruz, CA 95064, USA
| | - Kenneth Hoadley
- Ocean EcoSystems Biology Unit, RD3, GEOMAR Helmholtz Centre for Ocean Research, 24148 Kiel, DE
| | - Lisa Sudek
- Ocean Sciences Department, University of California Santa Cruz, Santa Cruz, CA 95064, USA
| | - Camille Poirier
- Ocean EcoSystems Biology Unit, RD3, GEOMAR Helmholtz Centre for Ocean Research, 24148 Kiel, DE
| | - Richard Dannebaum
- Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Edward Susko
- Department of Mathematics and Statistics, Dalhousie University, Halifax, Nova Scotia B3H 4R2, CA
| | - Alexandra Z Worden
- Ocean EcoSystems Biology Unit, RD3, GEOMAR Helmholtz Centre for Ocean Research, 24148 Kiel, DE
- Ocean Sciences Department, University of California Santa Cruz, Santa Cruz, CA 95064, USA
- Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, MA 02543, USA
- Max Planck Institute for Evolutionary Biology, 24306 Plön, DE
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7
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Tikhonov AN. Electron Transport in Chloroplasts: Regulation and Alternative Pathways of Electron Transfer. BIOCHEMISTRY. BIOKHIMIIA 2023; 88:1438-1454. [PMID: 38105016 DOI: 10.1134/s0006297923100036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 07/09/2023] [Accepted: 07/09/2023] [Indexed: 12/19/2023]
Abstract
This work represents an overview of electron transport regulation in chloroplasts as considered in the context of structure-function organization of photosynthetic apparatus in plants. Main focus of the article is on bifurcated oxidation of plastoquinol by the cytochrome b6f complex, which represents the rate-limiting step of electron transfer between photosystems II and I. Electron transport along the chains of non-cyclic, cyclic, and pseudocyclic electron flow, their relationships to generation of the trans-thylakoid difference in electrochemical potentials of protons in chloroplasts, and pH-dependent mechanisms of regulation of the cytochrome b6f complex are considered. Redox reactions with participation of molecular oxygen and ascorbate, alternative mediators of electron transport in chloroplasts, have also been discussed.
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8
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Kozuleva MA, Ivanov BN. Superoxide Anion Radical Generation in Photosynthetic Electron Transport Chain. BIOCHEMISTRY. BIOKHIMIIA 2023; 88:1045-1060. [PMID: 37758306 DOI: 10.1134/s0006297923080011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 06/16/2023] [Accepted: 06/18/2023] [Indexed: 10/03/2023]
Abstract
This review analyzes data available in the literature on the rates, characteristics, and mechanisms of oxygen reduction to a superoxide anion radical at the sites of photosynthetic electron transport chain where this reduction has been established. The existing assumptions about the role of the components of these sites in this process are critically examined using thermodynamic approaches and results of the recent studies. The process of O2 reduction at the acceptor side of PSI, which is considered the main site of this process taking place in the photosynthetic chain, is described in detail. Evolution of photosynthetic apparatus in the context of controlling the leakage of electrons to O2 is explored. The reasons limiting application of the results obtained with the isolated segments of the photosynthetic chain to estimate the rates of O2 reduction at the corresponding sites in the intact thylakoid membrane are discussed.
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Affiliation(s)
- Marina A Kozuleva
- Institute of Basic Biological Problems, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
| | - Boris N Ivanov
- Institute of Basic Biological Problems, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
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Dai J, Zheng M, He Y, Zhou Y, Wang M, Chen B. Real-time response counterattack strategy of tolerant microalgae Chlorella vulgaris MBFJNU-1 in original swine wastewater and free ammonia. BIORESOURCE TECHNOLOGY 2023; 377:128945. [PMID: 36958682 DOI: 10.1016/j.biortech.2023.128945] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 03/14/2023] [Accepted: 03/20/2023] [Indexed: 06/18/2023]
Abstract
This work was the first time to systematically clarify the potential tolerance mechanism of an indigenous Chlorella vulgaris MBFJNU-1 towards the free ammonia (FA) during the original swine wastewater (OSW) treatment by transcriptome analysis using C. vulgaris UETX395 as the control group. The obtained results showed that C. vulgaris MBFJNU-1 was found to be more resistant to the high levels of FA (115 mg/L) and OSW in comparison to C. vulgaris UETX395 (38 mg/L). Moreover, the transcriptomic results stated that some key pathways from arginine biosynthesis, electron generation and transmission, ATP synthesis in chloroplasts, and glutathione synthesis of C. vulgaris MBFJNU-1 were greatly related with the OSW and FA. Additionally, C. vulgaris MBFJNU-1 in OSW and FA performed similar results in the common differentially expressed genes from these mentioned pathways. Overall, these obtained results deliver essential details in microalgal biotechnology to treat swine wastewater and high free ammonia wastewater.
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Affiliation(s)
- Jingxuan Dai
- College of Life Science, Fujian Normal University, Fuzhou 350117, China
| | - Mingmin Zheng
- College of Life Science, Fujian Normal University, Fuzhou 350117, China; Engineering Research Center of Industrial Microbiology, Ministry of Education, Fujian Normal University, Fuzhou 350117, China.
| | - Yongjin He
- College of Life Science, Fujian Normal University, Fuzhou 350117, China; Engineering Research Center of Industrial Microbiology, Ministry of Education, Fujian Normal University, Fuzhou 350117, China
| | - Youcai Zhou
- College of Life Science, Fujian Normal University, Fuzhou 350117, China
| | - Mingzi Wang
- College of Life Science, Fujian Normal University, Fuzhou 350117, China; Engineering Research Center of Industrial Microbiology, Ministry of Education, Fujian Normal University, Fuzhou 350117, China
| | - Bilian Chen
- College of Life Science, Fujian Normal University, Fuzhou 350117, China; Engineering Research Center of Industrial Microbiology, Ministry of Education, Fujian Normal University, Fuzhou 350117, China
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10
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Saroussi S, Redekop P, Karns DAJ, Thomas DC, Wittkopp TM, Posewitz MC, Grossman AR. Restricting electron flow at cytochrome b6f when downstream electron acceptors are severely limited. PLANT PHYSIOLOGY 2023; 192:789-804. [PMID: 36960590 PMCID: PMC10231464 DOI: 10.1093/plphys/kiad185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 02/21/2023] [Accepted: 02/22/2023] [Indexed: 06/01/2023]
Abstract
Photosynthetic organisms frequently experience abiotic stress that restricts their growth and development. Under such circumstances, most absorbed solar energy cannot be used for CO2 fixation and can cause the photoproduction of reactive oxygen species (ROS) that can damage the photosynthetic reaction centers of PSI and PSII, resulting in a decline in primary productivity. This work describes a biological "switch" in the green alga Chlamydomonas reinhardtii that reversibly restricts photosynthetic electron transport (PET) at the cytochrome b6f (Cyt b6f) complex when the capacity for accepting electrons downstream of PSI is severely limited. We specifically show this restriction in STARCHLESS6 (sta6) mutant cells, which cannot synthesize starch when they are limited for nitrogen (growth inhibition) and subjected to a dark-to-light transition. This restriction represents a form of photosynthetic control that causes diminished electron flow to PSI and thereby prevents PSI photodamage but does not appear to rely on a ΔpH. Furthermore, when electron flow is restricted, the plastid alternative oxidase (PTOX) becomes active, functioning as an electron valve that dissipates some excitation energy absorbed by PSII and allows the formation of a proton motive force (PMF) that would drive some ATP production (potentially sustaining PSII repair and nonphotochemical quenching [NPQ]). The restriction at the Cyt b6f complex can be gradually relieved with continued illumination. This study provides insights into how PET responds to a marked reduction in availability of downstream electron acceptors and the protective mechanisms involved.
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Affiliation(s)
- Shai Saroussi
- Department of Plant Biology, The Carnegie Institution for Science, Stanford, CA 94305, USA
| | - Petra Redekop
- Department of Plant Biology, The Carnegie Institution for Science, Stanford, CA 94305, USA
| | - Devin A J Karns
- Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO 80401, USA
| | - Dylan C Thomas
- Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO 80401, USA
| | - Tyler M Wittkopp
- Department of Plant Biology, The Carnegie Institution for Science, Stanford, CA 94305, USA
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Matthew C Posewitz
- Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO 80401, USA
| | - Arthur R Grossman
- Department of Plant Biology, The Carnegie Institution for Science, Stanford, CA 94305, USA
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11
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Milrad Y, Nagy V, Elman T, Fadeeva M, Tóth SZ, Yacoby I. A PSII photosynthetic control is activated in anoxic cultures of green algae following illumination. Commun Biol 2023; 6:514. [PMID: 37173420 PMCID: PMC10182038 DOI: 10.1038/s42003-023-04890-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Accepted: 05/01/2023] [Indexed: 05/15/2023] Open
Abstract
Photosynthetic hydrogen production from microalgae is considered to have potential as a renewable energy source. Yet, the process has two main limitations holding it back from scaling up; (i) electron loss to competing processes, mainly carbon fixation and (ii) sensitivity to O2 which diminishes the expression and the activity of the hydrogenase enzyme catalyzing H2 production. Here we report a third, hitherto unknown challenge: We found that under anoxia, a slow-down switch is activated in photosystem II (PSII), diminishing the maximal photosynthetic productivity by three-fold. Using purified PSII and applying in vivo spectroscopic and mass spectrometric techniques on Chlamydomonas reinhardtii cultures, we show that this switch is activated under anoxia, within 10 s of illumination. Furthermore, we show that the recovery to the initial rate takes place following 15 min of dark anoxia, and propose a mechanism in which, modulation in electron transfer at the acceptor site of PSII diminishes its output. Such insights into the mechanism broaden our understanding of anoxic photosynthesis and its regulation in green algae and inspire new strategies to improve bio-energy yields.
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Affiliation(s)
- Yuval Milrad
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv, 69978, Israel
| | - Valéria Nagy
- Institute of Plant Biology, Biological Research Centre, Szeged, Temesvári krt. 62, H-6726 Szeged, Hungary
| | - Tamar Elman
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv, 69978, Israel
| | - Maria Fadeeva
- Department of Biochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv, 69978, Israel
| | - Szilvia Z Tóth
- Institute of Plant Biology, Biological Research Centre, Szeged, Temesvári krt. 62, H-6726 Szeged, Hungary
| | - Iftach Yacoby
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv, 69978, Israel.
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12
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Ozawa SI, Buchert F, Reuys R, Hippler M, Takahashi Y. Algal PETC-Pro171-Leu suppresses electron transfer in cytochrome b6f under acidic lumenal conditions. PLANT PHYSIOLOGY 2023; 191:1803-1817. [PMID: 36516417 PMCID: PMC10022631 DOI: 10.1093/plphys/kiac575] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Accepted: 11/22/2022] [Indexed: 06/17/2023]
Abstract
Linear photosynthetic electron flow (LEF) produces NADPH and generates a proton electrochemical potential gradient across the thylakoid membrane to synthesize ATP, both of which are required for CO2 fixation. As cellular demand for ATP and NADPH varies, cyclic electron flow (CEF) between Photosystem I and the cytochrome b6f complex (b6f) produces extra ATP. b6f regulates LEF and CEF via photosynthetic control, which is a pH-dependent b6f slowdown of plastoquinol oxidation at the lumenal site. This protection mechanism is triggered at more alkaline lumen pH in the pgr1 (proton gradient regulation 1) mutant of the vascular plant Arabidopsis (Arabidopsis thaliana), which contains a Pro194Leu substitution in the b6f Rieske Iron-sulfur protein Photosynthetic Electron Transfer C (PETC) subunit. In this work, we introduced the equivalent pgr1 mutation in the green alga Chlamydomonas reinhardtii to generate PETC-P171L. Consistent with the pgr1 phenotype, PETC-P171L displayed impaired NPQ induction along with slower photoautotrophic growth under high light conditions. Our data provide evidence that the ΔpH component in PETC-P171L depends on oxygen availability. Only under low oxygen conditions was the ΔpH component sufficient to trigger a phenotype in algal PETC-P171L where the mutant b6f was more restricted to oxidize the plastoquinol pool and showed diminished electron flow through the b6f complex. These results demonstrate that photosynthetic control of different stringency are established in C. reinhardtii depending on the cellular metabolism, and the lumen pH-sensitive PETC-P171L was generated to read out various associated effects.
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Affiliation(s)
| | - Felix Buchert
- Institute of Plant Biology and Biotechnology, University of Münster, 48143 Münster, Germany
| | - Ruby Reuys
- Institute of Plant Biology and Biotechnology, University of Münster, 48143 Münster, Germany
| | - Michael Hippler
- Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan
- Institute of Plant Biology and Biotechnology, University of Münster, 48143 Münster, Germany
| | - Yuichiro Takahashi
- Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan
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Structure of Photosystem I Supercomplex Isolated from a Chlamydomonas reinhardtii Cytochrome b6f Temperature-Sensitive Mutant. Biomolecules 2023; 13:biom13030537. [PMID: 36979472 PMCID: PMC10046768 DOI: 10.3390/biom13030537] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 02/22/2023] [Accepted: 03/11/2023] [Indexed: 03/18/2023] Open
Abstract
The unicellular green alga, Chlamydomonas reinhardtii, has been widely used as a model system to study photosynthesis. Its possibility to generate and analyze specific mutants has made it an excellent tool for mechanistic and biogenesis studies. Using negative selection of ultraviolet (UV) irradiation–mutated cells, we isolated a mutant (TSP9) with a single amino acid mutation in the Rieske protein of the cytochrome b6f complex. The W143R mutation in the petC gene resulted in total loss of cytochrome b6f complex function at the non-permissive temperature of 37 °C and recovery at the permissive temperature of 25 °C. We then isolated photosystem I (PSI) and photosystem II (PSII) supercomplexes from cells grown at the non-permissive temperature and determined the PSI structure with high-resolution cryogenic electron microscopy. There were several structural alterations compared with the structures obtained from wild-type cells. Our structural data suggest that the mutant responded by excluding the Lhca2, Lhca9, PsaL, and PsaH subunits. This structural alteration prevents state two transition, where LHCII migrates from PSII to bind to the PSI complex. We propose this as a possible response mechanism triggered by the TSP9 phenotype at the non-permissive temperature.
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14
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Li N, Wong WS, Feng L, Wang C, Wong KS, Zhang N, Yang W, Jiang Y, Jiang L, He JX. The thylakoid membrane protein NTA1 is an assembly factor of the cytochrome b 6f complex essential for chloroplast development in Arabidopsis. PLANT COMMUNICATIONS 2023; 4:100509. [PMID: 36560880 PMCID: PMC9860185 DOI: 10.1016/j.xplc.2022.100509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 12/18/2022] [Accepted: 12/21/2022] [Indexed: 06/17/2023]
Abstract
The cytochrome b6f (Cyt b6f) complex is a multisubunit protein complex in chloroplast thylakoid membranes required for photosynthetic electron transport. Here we report the isolation and characterization of the new tiny albino 1 (nta1) mutant in Arabidopsis, which has severe defects in Cyt b6f accumulation and chloroplast development. Gene cloning revealed that the nta1 phenotype was caused by disruption of a single nuclear gene, NTA1, which encodes an integral thylakoid membrane protein conserved across green algae and plants. Overexpression of NTA1 completely rescued the nta1 phenotype, and knockout of NTA1 in wild-type plants recapitulated the mutant phenotype. Loss of NTA1 function severely impaired the accumulation of multiprotein complexes related to photosynthesis in thylakoid membranes, particularly the components of Cyt b6f. NTA1 was shown to directly interact with four subunits (Cyt b6/PetB, PetD, PetG, and PetN) of Cyt b6f through the DUF1279 domain and C-terminal sequence to mediate their assembly. Taken together, our results identify NTA1 as a new and key regulator of chloroplast development that plays essential roles in assembly of the Cyt b6f complex by interacting with multiple Cyt b6f subunits.
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Affiliation(s)
- Na Li
- School of Life Sciences and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China
| | - Wing Shing Wong
- School of Life Sciences and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China
| | - Lei Feng
- School of Life Sciences and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China
| | - Chunming Wang
- School of Life Sciences and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China
| | - King Shing Wong
- School of Life Sciences and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China
| | - Nianhui Zhang
- Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan, China
| | - Wei Yang
- School of Life Sciences and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China
| | - Yueming Jiang
- Guangdong Provincial Key Laboratory of Applied Botany & Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement, Core Botanical Gardens, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
| | - Liwen Jiang
- School of Life Sciences and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China
| | - Jun-Xian He
- School of Life Sciences and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China.
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15
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Zhang S, Zou B, Cao P, Su X, Xie F, Pan X, Li M. Structural insights into photosynthetic cyclic electron transport. MOLECULAR PLANT 2023; 16:187-205. [PMID: 36540023 DOI: 10.1016/j.molp.2022.12.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 12/17/2022] [Accepted: 12/18/2022] [Indexed: 06/17/2023]
Abstract
During photosynthesis, light energy is utilized to drive sophisticated biochemical chains of electron transfers, converting solar energy into chemical energy that feeds most life on earth. Cyclic electron transfer/flow (CET/CEF) plays an essential role in efficient photosynthesis, as it balances the ATP/NADPH ratio required in various regulatory and metabolic pathways. Photosystem I, cytochrome b6f, and NADH dehydrogenase (NDH) are large multisubunit protein complexes embedded in the thylakoid membrane of the chloroplast and key players in NDH-dependent CEF pathway. Furthermore, small mobile electron carriers serve as shuttles for electrons between these membrane protein complexes. Efficient electron transfer requires transient interactions between these electron donors and acceptors. Structural biology has been a powerful tool to advance our knowledge of this important biological process. A number of structures of the membrane-embedded complexes, soluble electron carrier proteins, and transient complexes composed of both have now been determined. These structural data reveal detailed interacting patterns of these electron donor-acceptor pairs, thus allowing us to visualize the different parts of the electron transfer process. This review summarizes the current state of structural knowledge of three membrane complexes and their interaction patterns with mobile electron carrier proteins.
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Affiliation(s)
- Shumeng Zhang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Baohua Zou
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Peng Cao
- Faculty of Environment and Life, Beijing University of Technology, Beijing, China
| | - Xiaodong Su
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Fen Xie
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Xiaowei Pan
- College of Life Science, Capital Normal University, Beijing, China
| | - Mei Li
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
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16
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Penzler JF, Marino G, Reiter B, Kleine T, Naranjo B, Leister D. Commonalities and specialties in photosynthetic functions of PROTON GRADIENT REGULATION5 variants in Arabidopsis. PLANT PHYSIOLOGY 2022; 190:1866-1882. [PMID: 35946785 PMCID: PMC9614465 DOI: 10.1093/plphys/kiac362] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 07/13/2022] [Indexed: 05/19/2023]
Abstract
The PROTON GRADIENT REGULATION5 (PGR5) protein is required for trans-thylakoid proton gradient formation and acclimation to fluctuating light (FL). PGR5 functionally interacts with two other thylakoid proteins, PGR5-like 1 (PGRL1) and 2 (PGRL2); however, the molecular details of these interactions are largely unknown. In the Arabidopsis (Arabidopsis thaliana) pgr5-1 mutant, the PGR5G130S protein accumulates in only small amounts. In this work, we generated a knockout allele of PGR5 (pgr5-Cas) using CRISPR-Cas9 technology. Like pgr5-1, pgr5-Cas is seedling-lethal under FL, but photosynthesis and particularly cyclic electron flow, as well as chlorophyll content, are less severely affected in both pgr5-Cas and pgrl1ab (which lacks PGRL1 and PGR5) than in pgr5-1. These differences are associated with changes in the levels of 260 proteins, including components of the Calvin-Benson cycle, photosystems II and I, and the NDH complex, in pgr5-1 relative to the wild type (WT), pgr5-Cas, and pgrl1ab. Some of the differences between pgr5-1 and the other mutant lines could be tentatively assigned to second-site mutations in the pgr5-1 line, identified by whole-genome sequencing. However, others, particularly the more pronounced photosynthetic defects and PGRL1 depletion (compared to pgr5-Cas), are clearly due to specific negative effects of the amino-acid substitution in PGR5G130S, as demonstrated by complementation analysis. Moreover, pgr5-1 and pgr5-Cas plants are less tolerant to long-term exposure to high light than pgrl1ab plants. These results imply that, in addition to the previously reported necessity of PGRL1 for optimal PGR5 function, PGR5 is required alongside PGRL1 to avoid harmful effects on plant performance.
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Affiliation(s)
| | | | - Bennet Reiter
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, D-82152 Planegg-Martinsried, Germany
| | - Tatjana Kleine
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, D-82152 Planegg-Martinsried, Germany
| | | | - Dario Leister
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, D-82152 Planegg-Martinsried, Germany
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17
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Leister D, Marino G, Minagawa J, Dann M. An ancient function of PGR5 in iron delivery? TRENDS IN PLANT SCIENCE 2022; 27:971-980. [PMID: 35618596 DOI: 10.1016/j.tplants.2022.04.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2021] [Revised: 03/29/2022] [Accepted: 04/26/2022] [Indexed: 06/15/2023]
Abstract
In all phototrophic organisms, the photosynthetic apparatus must be protected from light-induced damage. One important mechanism that mitigates photodamage in plants is antimycin A (AA)-sensitive cyclic electron flow (CEF), the evolution of which remains largely obscure. Here we show that proton gradient regulation 5 (PGR5), a key protein involved in AA-sensitive CEF, displays intriguing commonalities - including sequence and structural features - with a group of ferritin-like proteins. We therefore propose that PGR5 may originally have been involved in prokaryotic iron mobilization and delivery, which facilitated a primordial type of CEF as a side effect. The abandonment of the bacterioferritin system during the transformation of cyanobacterial endosymbionts into chloroplasts might have allowed PGR5 to functionally specialize in CEF.
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Affiliation(s)
- Dario Leister
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, D-82152 Planegg-Martinsried, Germany
| | - Giada Marino
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, D-82152 Planegg-Martinsried, Germany
| | - Jun Minagawa
- Division of Environmental Photobiology, National Institute for Basic Biology, Okazaki 444-8585, Japan
| | - Marcel Dann
- Plant Molecular Biology, Faculty of Biology, Ludwig-Maximilians-Universität München, D-82152 Planegg-Martinsried, Germany; Division of Environmental Photobiology, National Institute for Basic Biology, Okazaki 444-8585, Japan.
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18
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Takahashi H. Cyclic electron flow A to Z. JOURNAL OF PLANT RESEARCH 2022; 135:539-541. [PMID: 35727481 DOI: 10.1007/s10265-022-01402-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Affiliation(s)
- Hiroko Takahashi
- Department of Biochemistry and Molecular Biology, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570, Japan.
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19
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Cryo-EM structures of the Synechocystis sp. PCC 6803 cytochrome b6f complex with and without the regulatory PetP subunit. Biochem J 2022; 479:1487-1503. [PMID: 35726684 PMCID: PMC9342900 DOI: 10.1042/bcj20220124] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2022] [Revised: 06/01/2022] [Accepted: 06/21/2022] [Indexed: 11/17/2022]
Abstract
In oxygenic photosynthesis, the cytochrome b6f (cytb6f) complex links the linear electron transfer (LET) reactions occurring at photosystems I and II and generates a transmembrane proton gradient via the Q-cycle. In addition to this central role in LET, cytb6f also participates in a range of processes including cyclic electron transfer (CET), state transitions and photosynthetic control. Many of the regulatory roles of cytb6f are facilitated by auxiliary proteins that differ depending upon the species, yet because of their weak and transient nature the structural details of these interactions remain unknown. An apparent key player in the regulatory balance between LET and CET in cyanobacteria is PetP, a ∼10 kDa protein that is also found in red algae but not in green algae and plants. Here, we used cryogenic electron microscopy to determine the structure of the Synechocystis sp. PCC 6803 cytb6f complex in the presence and absence of PetP. Our structures show that PetP interacts with the cytoplasmic side of cytb6f, displacing the C-terminus of the PetG subunit and shielding the C-terminus of cytochrome b6, which binds the heme cn cofactor that is suggested to mediate CET. The structures also highlight key differences in the mode of plastoquinone binding between cyanobacterial and plant cytb6f complexes, which we suggest may reflect the unique combination of photosynthetic and respiratory electron transfer in cyanobacterial thylakoid membranes. The structure of cytb6f from a model cyanobacterial species amenable to genetic engineering will enhance future site-directed mutagenesis studies of structure-function relationships in this crucial ET complex.
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20
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Ho TTH, Schwier C, Elman T, Fleuter V, Zinzius K, Scholz M, Yacoby I, Buchert F, Hippler M. Photosystem I light-harvesting proteins regulate photosynthetic electron transfer and hydrogen production. PLANT PHYSIOLOGY 2022; 189:329-343. [PMID: 35157085 PMCID: PMC9070821 DOI: 10.1093/plphys/kiac055] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 01/23/2022] [Indexed: 05/06/2023]
Abstract
Linear electron flow (LEF) and cyclic electron flow (CEF) compete for light-driven electrons transferred from the acceptor side of photosystem I (PSI). Under anoxic conditions, such highly reducing electrons also could be used for hydrogen (H2) production via electron transfer between ferredoxin and hydrogenase in the green alga Chlamydomonas reinhardtii. Partitioning between LEF and CEF is regulated through PROTON-GRADIENT REGULATION5 (PGR5). There is evidence that partitioning of electrons also could be mediated via PSI remodeling processes. This plasticity is linked to the dynamics of PSI-associated light-harvesting proteins (LHCAs) LHCA2 and LHCA9. These two unique light-harvesting proteins are distinct from all other LHCAs because they are loosely bound at the PSAL pole. Here, we investigated photosynthetic electron transfer and H2 production in single, double, and triple mutants deficient in PGR5, LHCA2, and LHCA9. Our data indicate that lhca2 and lhca9 mutants are efficient in photosynthetic electron transfer, that LHCA2 impacts the pgr5 phenotype, and that pgr5/lhca2 is a potent H2 photo-producer. In addition, pgr5/lhca2 and pgr5/lhca9 mutants displayed substantially different H2 photo-production kinetics. This indicates that the absence of LHCA2 or LHCA9 impacts H2 photo-production independently, despite both being attached at the PSAL pole, pointing to distinct regulatory capacities.
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Affiliation(s)
- Thi Thu Hoai Ho
- Institute of Plant Biology and Biotechnology, University of Münster, Münster 48143, Germany
- Faculty of Fisheries, University of Agriculture and Forestry, Hue University, Hue 530000, Vietnam
| | - Chris Schwier
- Institute of Plant Biology and Biotechnology, University of Münster, Münster 48143, Germany
| | - Tamar Elman
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Vera Fleuter
- Institute of Plant Biology and Biotechnology, University of Münster, Münster 48143, Germany
| | - Karen Zinzius
- Institute of Plant Biology and Biotechnology, University of Münster, Münster 48143, Germany
| | - Martin Scholz
- Institute of Plant Biology and Biotechnology, University of Münster, Münster 48143, Germany
| | - Iftach Yacoby
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Felix Buchert
- Institute of Plant Biology and Biotechnology, University of Münster, Münster 48143, Germany
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21
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Zhou Q, Wang C, Yamamoto H, Shikanai T. PTOX-dependent safety valve does not oxidize P700 during photosynthetic induction in the Arabidopsis pgr5 mutant. PLANT PHYSIOLOGY 2022; 188:1264-1276. [PMID: 34792607 PMCID: PMC8825263 DOI: 10.1093/plphys/kiab541] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 10/15/2021] [Indexed: 05/19/2023]
Abstract
Plastid terminal oxidase (PTOX) accepts electrons from plastoquinol to reduce molecular oxygen to water. We introduced the gene encoding Chlamydomonas reinhardtii (Cr)PTOX2 into the Arabidopsis (Arabidopsis thaliana) wild-type (WT) and proton gradient regulation5 (pgr5) mutant defective in cyclic electron transport around photosystem I (PSI). The accumulation of CrPTOX2 only mildly affected photosynthetic electron transport in the WT background during steady-state photosynthesis but partly complemented the induction of nonphotochemical quenching (NPQ) in the pgr5 background. During the induction of photosynthesis by actinic light (AL) of 130 µmol photons m-2 s-1, the high level of PSII yield (Y(II)) was induced immediately after the onset of AL in WT plants accumulating CrPTOX2. NPQ was more rapidly induced in the transgenic plants than in WT plants. P700 was also oxidized immediately after the onset of AL. Although CrPTOX2 does not directly induce a proton concentration gradient (ΔpH) across the thylakoid membrane, the coupled reaction of PSII generated ΔpH to induce NPQ and the downregulation of the cytochrome b6f complex. Rapid induction of Y(II) and NPQ was also observed in the pgr5 plants accumulating CrPTOX2. In contrast to the WT background, P700 was not oxidized in the pgr5 background. Although the thylakoid lumen was acidified by CrPTOX2, PGR5 was essential for oxidizing P700. In addition to acidification of the thylakoid lumen to downregulate the cytochrome b6f complex (donor-side regulation), PGR5 may be required for draining electrons from PSI by transferring them to the plastoquinone pool. We propose a reevaluation of the contribution of this acceptor-side regulation by PGR5 in the photoprotection of PSI.
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Affiliation(s)
- Qi Zhou
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Caijuan Wang
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Hiroshi Yamamoto
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Toshiharu Shikanai
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
- Author for communication:
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22
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Electron transfer via cytochrome b6f complex displays sensitivity to Antimycin A upon STT7 kinase activation. Biochem J 2022; 479:111-127. [PMID: 34981811 DOI: 10.1042/bcj20210802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 12/23/2021] [Accepted: 01/04/2022] [Indexed: 11/17/2022]
Abstract
The cytochrome b6f complex (b6f) has been initially considered as the ferredoxin-plastoquinone reductase (FQR) during cyclic electron flow (CEF) with photosystem I that is inhibited by antimycin A (AA). The binding of AA to the b6f Qi-site is aggravated by heme-ci, which challenged the FQR function of b6f during CEF. Alternative models suggest that PROTON GRADIENT REGULATION5 (PGR5) is involved in a b6f-independent, AA-sensitive FQR. Here, we show in Chlamydomonas reinhardtii that the b6f is conditionally inhibited by AA in vivo and that the inhibition did not require PGR5. Instead, activation of the STT7 kinase upon anaerobic treatment induced the AA sensitivity of b6f which was absent in stt7-1. However, a lock in State 2 due to persisting phosphorylation in the phosphatase double mutant pph1;pbcp did not increase AA sensitivity of electron transfer. The latter required a redox poise, supporting the view that state transitions and CEF are not coercively coupled. This suggests that the b6f-interacting kinase is required for structure-function modulation of the Qi-site under CEF favoring conditions. We propose that PGR5 and STT7 independently sustain AA-sensitive FQR activity of the b6f. Accordingly, PGR5-mediated electron injection into an STT7-modulated Qi-site drives a Mitchellian Q cycle in CEF conditions.
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23
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Trinh MDL, Masuda S. Chloroplast pH Homeostasis for the Regulation of Photosynthesis. FRONTIERS IN PLANT SCIENCE 2022; 13:919896. [PMID: 35693183 PMCID: PMC9174948 DOI: 10.3389/fpls.2022.919896] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 05/04/2022] [Indexed: 05/16/2023]
Abstract
The pH of various chloroplast compartments, such as the thylakoid lumen and stroma, is light-dependent. Light illumination induces electron transfer in the photosynthetic apparatus, coupled with proton translocation across the thylakoid membranes, resulting in acidification and alkalization of the thylakoid lumen and stroma, respectively. Luminal acidification is crucial for inducing regulatory mechanisms that protect photosystems against photodamage caused by the overproduction of reactive oxygen species (ROS). Stromal alkalization activates enzymes involved in the Calvin-Benson-Bassham (CBB) cycle. Moreover, proton translocation across the thylakoid membranes generates a proton gradient (ΔpH) and an electric potential (ΔΨ), both of which comprise the proton motive force (pmf) that drives ATP synthase. Then, the synthesized ATP is consumed in the CBB cycle and other chloroplast metabolic pathways. In the dark, the pH of both the chloroplast stroma and thylakoid lumen becomes neutral. Despite extensive studies of the above-mentioned processes, the molecular mechanisms of how chloroplast pH can be maintained at proper levels during the light phase for efficient activation of photosynthesis and other metabolic pathways and return to neutral levels during the dark phase remain largely unclear, especially in terms of the precise control of stromal pH. The transient increase and decrease in chloroplast pH upon dark-to-light and light-to-dark transitions have been considered as signals for controlling other biological processes in plant cells. Forward and reverse genetic screening approaches recently identified new plastid proteins involved in controlling ΔpH and ΔΨ across the thylakoid membranes and chloroplast proton/ion homeostasis. These proteins have been conserved during the evolution of oxygenic phototrophs and include putative photosynthetic protein complexes, proton transporters, and/or their regulators. Herein, we summarize the recently identified protein players that control chloroplast pH and influence photosynthetic efficiency in plants.
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Affiliation(s)
- Mai Duy Luu Trinh
- Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Shinji Masuda
- Department of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
- *Correspondence: Shinji Masuda,
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24
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Solymosi D, Shevela D, Allahverdiyeva Y. Nitric oxide represses photosystem II and NDH-1 in the cyanobacterium Synechocystis sp. PCC 6803. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2022; 1863:148507. [PMID: 34728155 DOI: 10.1016/j.bbabio.2021.148507] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Revised: 10/20/2021] [Accepted: 10/27/2021] [Indexed: 11/16/2022]
Abstract
Photosynthetic electron transfer comprises a series of light-induced redox reactions catalysed by multiprotein machinery in the thylakoid. These protein complexes possess cofactors susceptible to redox modifications by reactive small molecules. The gaseous radical nitric oxide (NO), a key signalling molecule in green algae and plants, has earlier been shown to bind to Photosystem (PS) II and obstruct electron transfer in plants. The effects of NO on cyanobacterial bioenergetics however, have long remained obscure. In this study, we exposed the model cyanobacterium Synechocystis sp. PCC 6803 to NO under anoxic conditions and followed changes in whole-cell fluorescence and oxidoreduction of P700 in vivo. Our results demonstrate that NO blocks photosynthetic electron transfer in cells by repressing PSII, PSI, and likely the NDH dehydrogenase-like complex 1 (NDH-1). We propose that iron‑sulfur clusters of NDH-1 complex may be affected by NO to such an extent that ferredoxin-derived electron injection to the plastoquinone pool, and thus cyclic electron transfer, may be inhibited. These findings reveal the profound effects of NO on Synechocystis cells and demonstrate the importance of controlled NO homeostasis in cyanobacteria.
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Affiliation(s)
- Daniel Solymosi
- Molecular Plant Biology, Department of Life Technologies, University of Turku, Turku, FI 20014, Finland
| | - Dmitry Shevela
- Chemical Biological Centre, Department of Chemistry, Umeå University, 90187 Umeå, Sweden
| | - Yagut Allahverdiyeva
- Molecular Plant Biology, Department of Life Technologies, University of Turku, Turku, FI 20014, Finland.
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25
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Vilyanen D, Naydov I, Ivanov B, Borisova-Mubarakshina M, Kozuleva M. Inhibition of plastoquinol oxidation at the cytochrome b 6f complex by dinitrophenyl ether of iodonitrothymol (DNP-INT) depends on irradiance and H + uptake by thylakoid membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2022; 1863:148506. [PMID: 34751144 DOI: 10.1016/j.bbabio.2021.148506] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 10/08/2021] [Accepted: 10/19/2021] [Indexed: 11/26/2022]
Abstract
Inhibitory analysis is a useful tool for studying reactions in the photosynthetic apparatus. After introducing by Aachim Trebst in 1978, dinitrophenylether of iodonitrothymol (DNP-INT), a competitive inhibitor of plastoquinol oxidation at the cytochrome (cyt.) b6f complex, has been widely applied to study reactions occurring in the plastoquinone pool and the cyt. b6f complex. Here we examine the inhibitory efficiency of DNP-INT by implementing three approaches to estimate the extent of blockage of electron flow from the plastoquinone pool to photosystem I in isolated thylakoids from spinach (Spinacia oleracea). We confirm that DNP-INT is a potent inhibitor of electron flow to photosystem I and demonstrate that inhibitory action of DNP-INT depends on irradiance and H+ uptake by thylakoid membranes. Based on these findings, we infer that affinity of the quinol-oxidizing site of the cyt. b6f complex to DNP-INT is increased in the light due to hydrogen bonding between DNP-INT molecules and acidic amino acid residue(s), which is (are) protonated in the light.
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Affiliation(s)
- Daria Vilyanen
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino, Russia
| | - Ilya Naydov
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino, Russia
| | - Boris Ivanov
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino, Russia
| | - Maria Borisova-Mubarakshina
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino, Russia
| | - Marina Kozuleva
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino, Russia.
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Caspy I, Schwartz T, Bayro-Kaiser V, Fadeeva M, Kessel A, Ben-Tal N, Nelson N. Dimeric and high-resolution structures of Chlamydomonas Photosystem I from a temperature-sensitive Photosystem II mutant. Commun Biol 2021; 4:1380. [PMID: 34887518 PMCID: PMC8660910 DOI: 10.1038/s42003-021-02911-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Accepted: 11/19/2021] [Indexed: 11/30/2022] Open
Abstract
Water molecules play a pivotal functional role in photosynthesis, primarily as the substrate for Photosystem II (PSII). However, their importance and contribution to Photosystem I (PSI) activity remains obscure. Using a high-resolution cryogenic electron microscopy (cryo-EM) PSI structure from a Chlamydomonas reinhardtii temperature-sensitive photoautotrophic PSII mutant (TSP4), a conserved network of water molecules - dating back to cyanobacteria - was uncovered, mainly in the vicinity of the electron transport chain (ETC). The high-resolution structure illustrated that the water molecules served as a ligand in every chlorophyll that was missing a fifth magnesium coordination in the PSI core and in the light-harvesting complexes (LHC). The asymmetric distribution of the water molecules near the ETC branches modulated their electrostatic landscape, distinctly in the space between the quinones and FX. The data also disclosed the first observation of eukaryotic PSI oligomerisation through a low-resolution PSI dimer that was comprised of PSI-10LHC and PSI-8LHC. Caspy et al. report the structure of PSI from a temperature-sensitive photoautotrophic PSII mutant of Chlamydomonas reinhardtii (TSP4), and report the distribution of conserved water molecules in the structure from cyanobacterial to higher plant PSI. They suggest that the asymmetric distribution of water molecules near the electron transfer chain modulates the electron transfer from quinones to FX.
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Affiliation(s)
- Ido Caspy
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Tom Schwartz
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Vinzenz Bayro-Kaiser
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Mariia Fadeeva
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Amit Kessel
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Nir Ben-Tal
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Nathan Nelson
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel.
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Hippler M, Nelson N. The Plasticity of Photosystem I. PLANT & CELL PHYSIOLOGY 2021; 62:1073-1081. [PMID: 33768246 DOI: 10.1093/pcp/pcab046] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2021] [Accepted: 02/09/2021] [Indexed: 06/12/2023]
Abstract
Most of life's energy comes from sunlight, and thus, photosynthesis underpins the survival of virtually all life forms. The light-driven electron transfer at photosystem I (PSI) is certainly the most important generator of reducing power at the cellular level and thereby largely determines the global amount of enthalpy in living systems (Nelson 2011). The PSI is a light-driven plastocyanin:ferredoxin oxidoreductase, which is embedded into thylakoid membranes of cyanobacteria and chloroplasts of eukaryotic photosynthetic organism. Structural determination of complexes of the photosynthetic machinery is vital for the understanding of its mode of action. Here, we describe new structural and functional insights into PSI and associated light-harvesting proteins, with a focus on the plasticity of PSI.
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Affiliation(s)
- Michael Hippler
- Institute of Plant Biology and Biotechnology, University of Münster, Münster 48143, Germany
- Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Nathan Nelson
- Institute of Plant Science and Resources, Okayama University, Kurashiki, Japan
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28
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Nikkanen L, Solymosi D, Jokel M, Allahverdiyeva Y. Regulatory electron transport pathways of photosynthesis in cyanobacteria and microalgae: Recent advances and biotechnological prospects. PHYSIOLOGIA PLANTARUM 2021; 173:514-525. [PMID: 33764547 DOI: 10.1111/ppl.13404] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2020] [Accepted: 03/12/2021] [Indexed: 06/12/2023]
Abstract
Cyanobacteria and microalgae perform oxygenic photosynthesis where light energy is harnessed to split water into oxygen and protons. This process releases electrons that are used by the photosynthetic electron transport chain to form reducing equivalents that provide energy for the cell metabolism. Constant changes in environmental conditions, such as light availability, temperature, and access to nutrients, create the need to balance the photochemical reactions and the metabolic demands of the cell. Thus, cyanobacteria and microalgae evolved several auxiliary electron transport (AET) pathways to disperse the potentially harmful over-supply of absorbed energy. AET pathways are comprised of electron sinks, e.g. flavodiiron proteins (FDPs) or other terminal oxidases, and pathways that recycle electrons around photosystem I, like NADPH-dehydrogenase-like complexes (NDH) or the ferredoxin-plastoquinone reductase (FQR). Under controlled conditions the need for these AET pathways is decreased and AET can even be energetically wasteful. Therefore, redirecting photosynthetic reducing equivalents to biotechnologically useful reactions, catalyzed by i.e. innate hydrogenases or heterologous enzymes, offers novel possibilities to apply photosynthesis research.
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Affiliation(s)
- Lauri Nikkanen
- Molecular Plant Biology, Department of Life Technologies, University of Turku, Turku, Finland
| | - Daniel Solymosi
- Molecular Plant Biology, Department of Life Technologies, University of Turku, Turku, Finland
| | - Martina Jokel
- Molecular Plant Biology, Department of Life Technologies, University of Turku, Turku, Finland
| | - Yagut Allahverdiyeva
- Molecular Plant Biology, Department of Life Technologies, University of Turku, Turku, Finland
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29
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Flannery SE, Pastorelli F, Wood WHJ, Hunter CN, Dickman MJ, Jackson PJ, Johnson MP. Comparative proteomics of thylakoids from Arabidopsis grown in laboratory and field conditions. PLANT DIRECT 2021; 5:e355. [PMID: 34712896 PMCID: PMC8528093 DOI: 10.1002/pld3.355] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 09/21/2021] [Accepted: 09/28/2021] [Indexed: 06/13/2023]
Abstract
Compared to controlled laboratory conditions, plant growth in the field is rarely optimal since it is frequently challenged by large fluctuations in light and temperature which lower the efficiency of photosynthesis and lead to photo-oxidative stress. Plants grown under natural conditions therefore place an increased onus on the regulatory mechanisms that protect and repair the delicate photosynthetic machinery. Yet, the exact changes in thylakoid proteome composition which allow plants to acclimate to the natural environment remain largely unexplored. Here, we use quantitative label-free proteomics to demonstrate that field-grown Arabidopsis plants incorporate aspects of both the low and high light acclimation strategies previously observed in laboratory-grown plants. Field plants showed increases in the relative abundance of ATP synthase, cytochrome b 6 f, ferredoxin-NADP+ reductases (FNR1 and FNR2) and their membrane tethers TIC62 and TROL, thylakoid architecture proteins CURT1A, CURT1B, RIQ1, and RIQ2, the minor monomeric antenna complex CP29.3, rapidly-relaxing non-photochemical quenching (qE)-related proteins PSBS and VDE, the photosystem II (PSII) repair machinery and the cyclic electron transfer complexes NDH, PGRL1B, and PGR5, in addition to decreases in the amounts of LHCII trimers composed of LHCB1.1, LHCB1.2, LHCB1.4, and LHCB2 proteins and CP29.2, all features typical of a laboratory high light acclimation response. Conversely, field plants also showed increases in the abundance of light harvesting proteins LHCB1.3 and CP29.1, zeaxanthin epoxidase (ZEP) and the slowly-relaxing non-photochemical quenching (qI)-related protein LCNP, changes previously associated with a laboratory low light acclimation response. Field plants also showed distinct changes to the proteome including the appearance of stress-related proteins ELIP1 and ELIP2 and changes to proteins that are largely invariant under laboratory conditions such as state transition related proteins STN7 and TAP38. We discuss the significance of these alterations in the thylakoid proteome considering the unique set of challenges faced by plants growing under natural conditions.
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Affiliation(s)
- Sarah E. Flannery
- Department of Molecular Biology and BiotechnologyUniversity of SheffieldSheffieldUK
| | - Federica Pastorelli
- Department of Molecular Biology and BiotechnologyUniversity of SheffieldSheffieldUK
| | - William H. J. Wood
- Department of Molecular Biology and BiotechnologyUniversity of SheffieldSheffieldUK
| | - C. Neil Hunter
- Department of Molecular Biology and BiotechnologyUniversity of SheffieldSheffieldUK
| | - Mark J. Dickman
- Department of Chemical and Biological EngineeringUniversity of SheffieldSheffieldUK
| | - Philip J. Jackson
- Department of Molecular Biology and BiotechnologyUniversity of SheffieldSheffieldUK
- Department of Chemical and Biological EngineeringUniversity of SheffieldSheffieldUK
| | - Matthew P. Johnson
- Department of Molecular Biology and BiotechnologyUniversity of SheffieldSheffieldUK
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30
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PGRL2 triggers degradation of PGR5 in the absence of PGRL1. Nat Commun 2021; 12:3941. [PMID: 34168134 PMCID: PMC8225790 DOI: 10.1038/s41467-021-24107-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2020] [Accepted: 06/01/2021] [Indexed: 12/01/2022] Open
Abstract
In plants, inactivation of either of the thylakoid proteins PGR5 and PGRL1 impairs cyclic electron flow (CEF) around photosystem I. Because PGR5 is unstable in the absence of the redox-active PGRL1, but not vice versa, PGRL1 is thought to be essential for CEF. However, we show here that inactivation of PGRL2, a distant homolog of PGRL1, relieves the need for PGRL1 itself. Conversely, high levels of PGRL2 destabilize PGR5 even when PGRL1 is present. In the absence of both PGRL1 and PGRL2, PGR5 alters thylakoid electron flow and impairs plant growth. Consequently, PGR5 can operate in CEF on its own, and is the target of the CEF inhibitor antimycin A, but its activity must be modulated by PGRL1. We conclude that PGRL1 channels PGR5 activity, and that PGRL2 triggers the degradation of PGR5 when the latter cannot productively interact with PGRL1. It is currently thought that the thylakoid proteins PGRL1 and PGR5 form a complex to mediate cyclic electron flow (CEF) around photosystem I. Here the authors show that CEF can in fact be mediated by PGR5 alone and that PGRL1 and the homologous PGRL2 modify the process by modulating PGR5 activity and stability.
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31
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NTRC Effects on Non-Photochemical Quenching Depends on PGR5. Antioxidants (Basel) 2021; 10:antiox10060900. [PMID: 34204867 PMCID: PMC8229092 DOI: 10.3390/antiox10060900] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 05/27/2021] [Accepted: 06/01/2021] [Indexed: 01/14/2023] Open
Abstract
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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32
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Milrad Y, Schweitzer S, Feldman Y, Yacoby I. Bi-directional electron transfer between H2 and NADPH mitigates light fluctuation responses in green algae. PLANT PHYSIOLOGY 2021; 186:168-179. [PMID: 33793951 PMCID: PMC8154092 DOI: 10.1093/plphys/kiab051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 01/21/2021] [Indexed: 05/05/2023]
Abstract
The metabolism of green algae has been the focus of much research over the last century. These photosynthetic organisms can thrive under various conditions and adapt quickly to changing environments by concomitant usage of several metabolic apparatuses. The main electron coordinator in their chloroplasts, nicotinamide adenine dinucleotide phosphate (NADPH), participates in many enzymatic activities and is also responsible for inter-organellar communication. Under anaerobic conditions, green algae also accumulate molecular hydrogen (H2), a promising alternative for fossil fuels. However, to scale-up its accumulation, a firm understanding of its integration in the photosynthetic apparatus is still required. While it is generally accepted that NADPH metabolism correlates to H2 accumulation, the mechanism of this collaboration is still vague and relies on indirect measurements. Here, we investigated this connection in Chlamydomonas reinhardtii using simultaneous measurements of both dissolved gases concentration, NADPH fluorescence and electrochromic shifts at 520-546 nm. Our results indicate that energy transfer between H2 and NADPH is bi-directional and crucial for the maintenance of redox balance under light fluctuations. At light onset, NADPH consumption initially eventuates in H2 evolution, which initiates the photosynthetic electron flow. Later on, as illumination continues the majority of NADPH is diverted to the Calvin-Benson-Bassham cycle. Dark onset triggers re-assimilation of H2, which produces NADPH and so, enables initiation of dark fermentative metabolism.
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Affiliation(s)
- Yuval Milrad
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
| | - Shira Schweitzer
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
| | - Yael Feldman
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
| | - Iftach Yacoby
- School of Plant Sciences and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
- Author for communication: (I.Y.)
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33
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Photosynthetic Linear Electron Flow Drives CO 2 Assimilation in Maize Leaves. Int J Mol Sci 2021; 22:ijms22094894. [PMID: 34063101 PMCID: PMC8124781 DOI: 10.3390/ijms22094894] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 05/02/2021] [Accepted: 05/04/2021] [Indexed: 12/24/2022] Open
Abstract
Photosynthetic organisms commonly develop the strategy to keep the reaction center chlorophyll of photosystem I, P700, oxidized for preventing the generation of reactive oxygen species in excess light conditions. In photosynthesis of C4 plants, CO2 concentration is kept at higher levels around ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) by the cooperation of the mesophyll and bundle sheath cells, which enables them to assimilate CO2 at higher rates to survive under drought stress. However, the regulatory mechanism of photosynthetic electron transport for P700 oxidation is still poorly understood in C4 plants. Here, we assessed gas exchange, chlorophyll fluorescence, electrochromic shift, and near infrared absorbance in intact leaves of maize (a NADP-malic enzyme C4 subtype species) in comparison with mustard, a C3 plant. Instead of the alternative electron sink due to photorespiration in the C3 plant, photosynthetic linear electron flow was strongly suppressed between photosystems I and II, dependent on the difference of proton concentration across the thylakoid membrane (ΔpH) in response to the suppression of CO2 assimilation in maize. Linear relationships among CO2 assimilation rate, linear electron flow, P700 oxidation, ΔpH, and the oxidation rate of ferredoxin suggested that the increase of ΔpH for P700 oxidation was caused by the regulation of proton conductance of chloroplast ATP synthase but not by promoting cyclic electron flow. At the scale of intact leaves, the ratio of PSI to PSII was estimated almost 1:1 in both C3 and C4 plants. Overall, the photosynthetic electron transport was regulated for P700 oxidation in maize through the same strategies as in C3 plants only except for the capacity of photorespiration despite the structural and metabolic differences in photosynthesis between C3 and C4 plants.
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34
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Kramer M, Rodriguez-Heredia M, Saccon F, Mosebach L, Twachtmann M, Krieger-Liszkay A, Duffy C, Knell RJ, Finazzi G, Hanke GT. Regulation of photosynthetic electron flow on dark to light transition by ferredoxin:NADP(H) oxidoreductase interactions. eLife 2021; 10:56088. [PMID: 33685582 PMCID: PMC7984839 DOI: 10.7554/elife.56088] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 02/25/2021] [Indexed: 01/12/2023] Open
Abstract
During photosynthesis, electron transport is necessary for carbon assimilation and must be regulated to minimize free radical damage. There is a longstanding controversy over the role of a critical enzyme in this process (ferredoxin:NADP(H) oxidoreductase, or FNR), and in particular its location within chloroplasts. Here we use immunogold labelling to prove that FNR previously assigned as soluble is in fact membrane associated. We combined this technique with a genetic approach in the model plant Arabidopsis to show that the distribution of this enzyme between different membrane regions depends on its interaction with specific tether proteins. We further demonstrate a correlation between the interaction of FNR with different proteins and the activity of alternative photosynthetic electron transport pathways. This supports a role for FNR location in regulating photosynthetic electron flow during the transition from dark to light.
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Affiliation(s)
- Manuela Kramer
- School of Biochemistry and Chemistry, Queen Mary University of London, London, United Kingdom.,Department of Plant Physiology, Faculty of Biology and Chemistry, University of Osnabrück, Osnabrück, Germany
| | | | - Francesco Saccon
- School of Biochemistry and Chemistry, Queen Mary University of London, London, United Kingdom
| | - Laura Mosebach
- Institute of Plant Biology and Biotechnology, University of Münster, Münster, Germany
| | - Manuel Twachtmann
- Department of Plant Physiology, Faculty of Biology and Chemistry, University of Osnabrück, Osnabrück, Germany
| | - Anja Krieger-Liszkay
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay, Paris, France
| | - Chris Duffy
- School of Biochemistry and Chemistry, Queen Mary University of London, London, United Kingdom
| | - Robert J Knell
- School of Biochemistry and Chemistry, Queen Mary University of London, London, United Kingdom
| | - Giovanni Finazzi
- Laboratoire de Physiologie Cellulaire et Végétale, UMR 5168, Centre National de la Recherche Scientifique (CNRS), Commissariat a` l'Energie Atomique et aux Energies Alternatives (CEA), Université Grenoble Alpes, Institut National Recherche Agronomique (INRA), Institut de Recherche en Sciences et Technologies pour le Vivant (iRTSV), CEA Grenoble, Grenoble, France
| | - Guy Thomas Hanke
- School of Biochemistry and Chemistry, Queen Mary University of London, London, United Kingdom.,Department of Plant Physiology, Faculty of Biology and Chemistry, University of Osnabrück, Osnabrück, Germany
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35
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Wu X, Wu J, Wang Y, He M, He M, Liu W, Shu S, Sun J, Guo S. The key cyclic electron flow protein PGR5 associates with cytochrome b 6f, and its function is partially influenced by the LHCII state transition. HORTICULTURE RESEARCH 2021; 8:55. [PMID: 33664242 PMCID: PMC7933433 DOI: 10.1038/s41438-021-00460-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 10/30/2020] [Accepted: 11/20/2020] [Indexed: 05/08/2023]
Abstract
In plants and algae, PGR5-dependent cyclic electron flow (CEF) is an important regulator of acclimation to fluctuating environments, but how PGR5 participates in CEF is unclear. In this work, we analyzed two PGR5s in cucumber (Cucumis sativus L.) under different conditions and found that CsPGR5a played the dominant role in PGR5-dependent CEF. The results of yeast two-hybrid, biomolecular fluorescence complementation (BiFC), blue native PAGE, and coimmunoprecipitation (CoIP) assays showed that PGR5a interacted with PetC, Lhcb3, and PsaH. Furthermore, the intensity of the interactions was dynamic during state transitions, and the abundance of PGR5 attached to cyt b6f decreased during the transition from state 1 to state 2, which revealed that the function of PGR5a is related to the state transition. We proposed that PGR5 is a small mobile protein that functions when attached to protein complexes.
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Affiliation(s)
- Xinyi Wu
- College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Jianqiang Wu
- College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Yu Wang
- College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Meiwen He
- College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Mingming He
- College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Weikang Liu
- College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
| | - Sheng Shu
- College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China
- Nanjing Agricultural University (Suqian) Academy of Protected Horticulture, Jiangsu, Suqian, 223800, China
| | - Jin Sun
- College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China.
- Nanjing Agricultural University (Suqian) Academy of Protected Horticulture, Jiangsu, Suqian, 223800, China.
| | - Shirong Guo
- College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China.
- Nanjing Agricultural University (Suqian) Academy of Protected Horticulture, Jiangsu, Suqian, 223800, China.
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36
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Malone LA, Proctor MS, Hitchcock A, Hunter CN, Johnson MP. Cytochrome b 6f - Orchestrator of photosynthetic electron transfer. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2021; 1862:148380. [PMID: 33460588 DOI: 10.1016/j.bbabio.2021.148380] [Citation(s) in RCA: 51] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 01/06/2021] [Accepted: 01/09/2021] [Indexed: 11/18/2022]
Abstract
Cytochrome b6f (cytb6f) lies at the heart of the light-dependent reactions of oxygenic photosynthesis, where it serves as a link between photosystem II (PSII) and photosystem I (PSI) through the oxidation and reduction of the electron carriers plastoquinol (PQH2) and plastocyanin (Pc). A mechanism of electron bifurcation, known as the Q-cycle, couples electron transfer to the generation of a transmembrane proton gradient for ATP synthesis. Cytb6f catalyses the rate-limiting step in linear electron transfer (LET), is pivotal for cyclic electron transfer (CET) and plays a key role as a redox-sensing hub involved in the regulation of light-harvesting, electron transfer and photosynthetic gene expression. Together, these characteristics make cytb6f a judicious target for genetic manipulation to enhance photosynthetic yield, a strategy which already shows promise. In this review we will outline the structure and function of cytb6f with a particular focus on new insights provided by the recent high-resolution map of the complex from Spinach.
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Affiliation(s)
- Lorna A Malone
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | - Matthew S Proctor
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | - Andrew Hitchcock
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | - C Neil Hunter
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | - Matthew P Johnson
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK.
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37
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Hepworth C, Wood WHJ, Emrich-Mills TZ, Proctor MS, Casson S, Johnson MP. Dynamic thylakoid stacking and state transitions work synergistically to avoid acceptor-side limitation of photosystem I. NATURE PLANTS 2021. [PMID: 33432159 DOI: 10.1038/s41477-020-00828-823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
TAP38/STN7-dependent (de)phosphorylation of light-harvesting complex II (LHCII) regulates the relative excitation rates of photosystems I and II (PSI, PSII) (state transitions) and the size of the thylakoid grana stacks (dynamic thylakoid stacking). Yet, it remains unclear how changing grana size benefits photosynthesis and whether these two regulatory mechanisms function independently. Here, by comparing Arabidopsis wild-type, stn7 and tap38 plants with the psal mutant, which undergoes dynamic thylakoid stacking but lacks state transitions, we explain their distinct roles. Under low light, smaller grana increase the rate of PSI reduction and photosynthesis by reducing the diffusion distance for plastoquinol; however, this beneficial effect is only apparent when PSI/PSII excitation balance is maintained by state transitions or far-red light. Under high light, the larger grana slow plastoquinol diffusion and lower the equilibrium constant between plastocyanin and PSI, maximizing photosynthesis by avoiding PSI photoinhibition. Loss of state transitions in low light or maintenance of smaller grana in high light also both bring about a decrease in cyclic electron transfer and over-reduction of the PSI acceptor side. These results demonstrate that state transitions and dynamic thylakoid stacking work synergistically to regulate photosynthesis in variable light.
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Affiliation(s)
- Christopher Hepworth
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, UK
| | - William H J Wood
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, UK
| | - Tom Z Emrich-Mills
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, UK
| | - Matthew S Proctor
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, UK
| | - Stuart Casson
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, UK
| | - Matthew P Johnson
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, UK.
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Hepworth C, Wood WHJ, Emrich-Mills TZ, Proctor MS, Casson S, Johnson MP. Dynamic thylakoid stacking and state transitions work synergistically to avoid acceptor-side limitation of photosystem I. NATURE PLANTS 2021; 7:87-98. [PMID: 33432159 DOI: 10.1038/s41477-020-00828-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 12/04/2020] [Indexed: 05/11/2023]
Abstract
TAP38/STN7-dependent (de)phosphorylation of light-harvesting complex II (LHCII) regulates the relative excitation rates of photosystems I and II (PSI, PSII) (state transitions) and the size of the thylakoid grana stacks (dynamic thylakoid stacking). Yet, it remains unclear how changing grana size benefits photosynthesis and whether these two regulatory mechanisms function independently. Here, by comparing Arabidopsis wild-type, stn7 and tap38 plants with the psal mutant, which undergoes dynamic thylakoid stacking but lacks state transitions, we explain their distinct roles. Under low light, smaller grana increase the rate of PSI reduction and photosynthesis by reducing the diffusion distance for plastoquinol; however, this beneficial effect is only apparent when PSI/PSII excitation balance is maintained by state transitions or far-red light. Under high light, the larger grana slow plastoquinol diffusion and lower the equilibrium constant between plastocyanin and PSI, maximizing photosynthesis by avoiding PSI photoinhibition. Loss of state transitions in low light or maintenance of smaller grana in high light also both bring about a decrease in cyclic electron transfer and over-reduction of the PSI acceptor side. These results demonstrate that state transitions and dynamic thylakoid stacking work synergistically to regulate photosynthesis in variable light.
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Affiliation(s)
- Christopher Hepworth
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, UK
| | - William H J Wood
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, UK
| | - Tom Z Emrich-Mills
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, UK
| | - Matthew S Proctor
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, UK
| | - Stuart Casson
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, UK
| | - Matthew P Johnson
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, UK.
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Shimakawa G, Hanawa H, Wada S, Hanke GT, Matsuda Y, Miyake C. Physiological Roles of Flavodiiron Proteins and Photorespiration in the Liverwort Marchantia polymorpha. FRONTIERS IN PLANT SCIENCE 2021; 12:668805. [PMID: 34489990 PMCID: PMC8418088 DOI: 10.3389/fpls.2021.668805] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 07/30/2021] [Indexed: 05/19/2023]
Abstract
Against the potential risk in oxygenic photosynthesis, that is, the generation of reactive oxygen species, photosynthetic electron transport needs to be regulated in response to environmental fluctuations. One of the most important regulations is keeping the reaction center chlorophyll (P700) of photosystem I in its oxidized form in excess light conditions. The oxidation of P700 is supported by dissipating excess electrons safely to O2, and we previously found that the molecular mechanism of the alternative electron sink is changed from flavodiiron proteins (FLV) to photorespiration in the evolutionary history from cyanobacteria to plants. However, the overall picture of the regulation of photosynthetic electron transport is still not clear in bryophytes, the evolutionary intermediates. Here, we investigated the physiological roles of FLV and photorespiration for P700 oxidation in the liverwort Marchantia polymorpha by using the mutants deficient in FLV (flv1) at different O2 partial pressures. The effective quantum yield of photosystem II significantly decreased at 2kPa O2 in flv1, indicating that photorespiration functions as the electron sink. Nevertheless, it was clear from the phenotype of flv1 that FLV was dominant for P700 oxidation in M. polymorpha. These data suggested that photorespiration has yet not replaced FLV in functioning for P700 oxidation in the basal land plant probably because of the lower contribution to lumen acidification, compared with FLV, as reflected in the results of electrochromic shift analysis.
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Affiliation(s)
- Ginga Shimakawa
- Graduate School of Agricultural Science, Kobe University, Kobe, Japan
- Research Center for Solar Energy Chemistry, Osaka University, Suita, Japan
- Department of Biosciences, School of Biological and Environmental Sciences, Kwansei-Gakuin University, Nishinomiya, Japan
- Core Research for Environmental Science and Technology, Japan Science and Technology Agency, Chiyoda, Japan
| | - Hitomi Hanawa
- Graduate School of Agricultural Science, Kobe University, Kobe, Japan
| | - Shinya Wada
- Graduate School of Agricultural Science, Kobe University, Kobe, Japan
- Core Research for Environmental Science and Technology, Japan Science and Technology Agency, Chiyoda, Japan
| | - Guy T. Hanke
- School of Biochemistry and Chemistry, Queen Mary University of London, London, United Kingdom
| | - Yusuke Matsuda
- Department of Biosciences, School of Biological and Environmental Sciences, Kwansei-Gakuin University, Nishinomiya, Japan
| | - Chikahiro Miyake
- Graduate School of Agricultural Science, Kobe University, Kobe, Japan
- Core Research for Environmental Science and Technology, Japan Science and Technology Agency, Chiyoda, Japan
- *Correspondence: Chikahiro Miyake,
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Flannery SE, Hepworth C, Wood WHJ, Pastorelli F, Hunter CN, Dickman MJ, Jackson PJ, Johnson MP. Developmental acclimation of the thylakoid proteome to light intensity in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 105:223-244. [PMID: 33118270 PMCID: PMC7898487 DOI: 10.1111/tpj.15053] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 10/13/2020] [Accepted: 10/21/2020] [Indexed: 05/03/2023]
Abstract
Photosynthetic acclimation, the ability to adjust the composition of the thylakoid membrane to optimise the efficiency of electron transfer to the prevailing light conditions, is crucial to plant fitness in the field. While much is known about photosynthetic acclimation in Arabidopsis, to date there has been no study that combines both quantitative label-free proteomics and photosynthetic analysis by gas exchange, chlorophyll fluorescence and P700 absorption spectroscopy. Using these methods we investigated how the levels of 402 thylakoid proteins, including many regulatory proteins not previously quantified, varied upon long-term (weeks) acclimation of Arabidopsis to low (LL), moderate (ML) and high (HL) growth light intensity and correlated these with key photosynthetic parameters. We show that changes in the relative abundance of cytb6 f, ATP synthase, FNR2, TIC62 and PGR6 positively correlate with changes in estimated PSII electron transfer rate and CO2 assimilation. Improved photosynthetic capacity in HL grown plants is paralleled by increased cyclic electron transport, which positively correlated with NDH, PGRL1, FNR1, FNR2 and TIC62, although not PGR5 abundance. The photoprotective acclimation strategy was also contrasting, with LL plants favouring slowly reversible non-photochemical quenching (qI), which positively correlated with LCNP, while HL plants favoured rapidly reversible quenching (qE), which positively correlated with PSBS. The long-term adjustment of thylakoid membrane grana diameter positively correlated with LHCII levels, while grana stacking negatively correlated with CURT1 and RIQ protein abundance. The data provide insights into how Arabidopsis tunes photosynthetic electron transfer and its regulation during developmental acclimation to light intensity.
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Affiliation(s)
- Sarah E. Flannery
- Department of Molecular Biology and BiotechnologyUniversity of SheffieldFirth CourtWestern BankSheffieldUK
| | - Christopher Hepworth
- Department of Molecular Biology and BiotechnologyUniversity of SheffieldFirth CourtWestern BankSheffieldUK
| | - William H. J. Wood
- Department of Molecular Biology and BiotechnologyUniversity of SheffieldFirth CourtWestern BankSheffieldUK
| | - Federica Pastorelli
- Department of Molecular Biology and BiotechnologyUniversity of SheffieldFirth CourtWestern BankSheffieldUK
| | - Christopher N. Hunter
- Department of Molecular Biology and BiotechnologyUniversity of SheffieldFirth CourtWestern BankSheffieldUK
| | - Mark J. Dickman
- Department of Chemical and Biological EngineeringChELSI InstituteUniversity of SheffieldSheffieldUK
| | - Philip J. Jackson
- Department of Molecular Biology and BiotechnologyUniversity of SheffieldFirth CourtWestern BankSheffieldUK
- Department of Chemical and Biological EngineeringChELSI InstituteUniversity of SheffieldSheffieldUK
| | - Matthew P. Johnson
- Department of Molecular Biology and BiotechnologyUniversity of SheffieldFirth CourtWestern BankSheffieldUK
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Chouhan N, Devadasu E, Yadav RM, Subramanyam R. Autophagy Induced Accumulation of Lipids in pgrl1 and pgr5 of Chlamydomonas reinhardtii Under High Light. FRONTIERS IN PLANT SCIENCE 2021; 12:752634. [PMID: 35145528 PMCID: PMC8821104 DOI: 10.3389/fpls.2021.752634] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 12/20/2021] [Indexed: 05/03/2023]
Abstract
Chlamydomonas (C.) reinhardtii is a potential microalga for lipid production. Autophagy-triggered lipid metabolism in microalgae has not being studied so far from a mutant of proton gradient regulation 1 like (PGRL1) and proton gradient regulation 5 (PGR5). In this study, C. reinhardtii cells (wild-type CC124 and cyclic electron transport dependant mutants pgrl1 and pgr5) were grown photoheterotrophically in high light 500 μmol photons m-2 s-1, where pgr5 growth was retarded due to an increase in reactive oxygen species (ROS). The lipid contents were increased; however, carbohydrate content was decreased in pgr5. Further, the Nile Red (NR) fluorescence shows many lipid bodies in pgr5 cells under high light. Similarly, the electron micrographs show that large vacuoles were formed in high light stress despite the grana stacks structure. We also observed increased production of reactive oxygen species, which could be one reason the cells underwent autophagy. Further, a significant increase of autophagy ATG8 and detections of ATG8-PE protein was noticed in pgr5, a hallmark characteristic for autophagy formation. Consequently, the triacylglycerol (TAG) content was increased due to diacylglycerol acyltransferases (DGAT) and phospholipid diacylglycerol acyl-transference (PDAT) enzymes' expression, especially in pgr5. Here the TAG synthesis would have been obtained from degraded membrane lipids in pgr5. Additionally, mono, polyunsaturated, and saturated fatty acids were identified more in the high light condition. Our study shows that the increased light induces the reactive oxygen species, which leads to autophagy and TAG accumulation. Therefore, the enhanced accumulation of TAGs can be used as feedstock for biodiesel production and aqua feed.
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