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Chiu YF, Chu HA. New Structural and Mechanistic Insights Into Functional Roles of Cytochrome b 559 in Photosystem II. FRONTIERS IN PLANT SCIENCE 2022; 13:914922. [PMID: 35755639 PMCID: PMC9214863 DOI: 10.3389/fpls.2022.914922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 04/27/2022] [Indexed: 06/15/2023]
Abstract
Cytochrome (Cyt) b 559 is a key component of the photosystem II (PSII) complex for its assembly and proper function. Previous studies have suggested that Cytb 559 has functional roles in early assembly of PSII and in secondary electron transfer pathways that protect PSII against photoinhibition. In addition, the Cytb 559 in various PSII preparations exhibited multiple different redox potential forms. However, the precise functional roles of Cytb 559 in PSII remain unclear. Recent site-directed mutagenesis studies combined with functional genomics and biochemical analysis, as well as high-resolution x-ray crystallography and cryo-electron microscopy studies on native, inactive, and assembly intermediates of PSII have provided important new structural and mechanistic insights into the functional roles of Cytb 559. This mini-review gives an overview of new exciting results and their significance for understanding the structural and functional roles of Cytb 559 in PSII.
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Bicarbonate-controlled reduction of oxygen by the Q A semiquinone in Photosystem II in membranes. Proc Natl Acad Sci U S A 2022; 119:2116063119. [PMID: 35115403 PMCID: PMC8833163 DOI: 10.1073/pnas.2116063119] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/23/2021] [Indexed: 12/15/2022] Open
Abstract
In Photosystem II (PSII), O2 reduction by QA•− is often discussed but has not been demonstrated. Here, we show in PSII membranes that QA•− can reduce O2 to superoxide, but only when bicarbonate is absent from its binding site on the nonheme Fe2+. Bicarbonate’s role in PSII was recently shown to involve a regulatory/protective redox-tuning mechanism linking PSII function to CO2 concentration. A key aspect is the presence of stable QA•− causing release of bicarbonate from its site on Fe2+. Here, we show that under these conditions, O2 binds to the empty site on the Fe2+ and is reduced by QA•−. This unexpected reaction may be a further indication of cross-talk between the regulation of PSII and CO2 fixation. Photosystem II (PSII), the water/plastoquinone photo-oxidoreductase, plays a key energy input role in the biosphere. QA•−, the reduced semiquinone form of the nonexchangeable quinone, is often considered capable of a side reaction with O2, forming superoxide, but this reaction has not yet been demonstrated experimentally. Here, using chlorophyll fluorescence in plant PSII membranes, we show that O2 does oxidize QA•− at physiological O2 concentrations with a t1/2 of 10 s. Superoxide is formed stoichiometrically, and the reaction kinetics are controlled by the accessibility of O2 to a binding site near QA•−, with an apparent dissociation constant of 70 ± 20 µM. Unexpectedly, QA•− could only reduce O2 when bicarbonate was absent from its binding site on the nonheme iron (Fe2+) and the addition of bicarbonate or formate blocked the O2-dependant decay of QA•−. These results, together with molecular dynamics simulations and hybrid quantum mechanics/molecular mechanics calculations, indicate that electron transfer from QA•− to O2 occurs when the O2 is bound to the empty bicarbonate site on Fe2+. A protective role for bicarbonate in PSII was recently reported, involving long-lived QA•− triggering bicarbonate dissociation from Fe2+ [Brinkert et al., Proc. Natl. Acad. Sci. U.S.A. 113, 12144–12149 (2016)]. The present findings extend this mechanism by showing that bicarbonate release allows O2 to bind to Fe2+ and to oxidize QA•−. This could be beneficial by oxidizing QA•− and by producing superoxide, a chemical signal for the overreduced state of the electron transfer chain.
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Fu HY, Ghandour R, Ruf S, Zoschke R, Bock R, Schöttler MA. The availability of neither D2 nor CP43 limits the biogenesis of photosystem II in tobacco. PLANT PHYSIOLOGY 2021; 185:1111-1130. [PMID: 33793892 PMCID: PMC8133689 DOI: 10.1093/plphys/kiaa052] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 11/17/2020] [Indexed: 06/12/2023]
Abstract
The pathway of photosystem II (PSII) assembly is well understood, and multiple auxiliary proteins supporting it have been identified, but little is known about rate-limiting steps controlling PSII biogenesis. In the cyanobacterium Synechocystis PCC6803 and the green alga Chlamydomonas reinhardtii, indications exist that the biosynthesis of the chloroplast-encoded D2 reaction center subunit (PsbD) limits PSII accumulation. To determine the importance of D2 synthesis for PSII accumulation in vascular plants and elucidate the contributions of transcriptional and translational regulation, we modified the 5'-untranslated region of psbD via chloroplast transformation in tobacco (Nicotiana tabacum). A drastic reduction in psbD mRNA abundance resulted in a strong decrease in PSII content, impaired photosynthetic electron transport, and retarded growth under autotrophic conditions. Overexpression of the psbD mRNA also increased transcript abundance of psbC (the CP43 inner antenna protein), which is co-transcribed with psbD. Because translation efficiency remained unaltered, translation output of pbsD and psbC increased with mRNA abundance. However, this did not result in increased PSII accumulation. The introduction of point mutations into the Shine-Dalgarno-like sequence or start codon of psbD decreased translation efficiency without causing pronounced effects on PSII accumulation and function. These data show that neither transcription nor translation of psbD and psbC are rate-limiting for PSII biogenesis in vascular plants and that PSII assembly and accumulation in tobacco are controlled by different mechanisms than in cyanobacteria or in C. reinhardtii.
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Affiliation(s)
- Han-Yi Fu
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam, Germany
| | - Rabea Ghandour
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam, Germany
| | - Stephanie Ruf
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam, Germany
| | - Reimo Zoschke
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam, Germany
| | - Ralph Bock
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam, Germany
| | - Mark Aurel Schöttler
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam, Germany
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Nitrogen Sources and Iron Availability Affect Pigment Biosynthesis and Nutrient Consumption in Anabaena sp. UTEX 2576. Microorganisms 2021; 9:microorganisms9020431. [PMID: 33669780 PMCID: PMC7922959 DOI: 10.3390/microorganisms9020431] [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: 01/06/2021] [Revised: 02/15/2021] [Accepted: 02/16/2021] [Indexed: 11/17/2022] Open
Abstract
Anabaena sp. UTEX 2576 metabolizes multiple nitrogen (N) sources and is deemed a biotechnological platform for chemical production. Cyanobacteria have been identified as prolific producers of biofertilizers, biopolymers, biofuels, and other bioactive compounds. Here, we analyze the effect of different N-sources and Fe availability on the bioproduction of phycobiliproteins and β-carotene. We characterize nutrient demand in modified BG11 media, including data on CO2 fixation rates, N-source consumption, and mineral utilization (e.g., phosphorus (P), and 11 metallic elements). Results suggest that non-diazotrophic cultures grow up to 60% faster than diazotrophic cells, resulting in 20% higher CO2-fixation rates. While the production of β-carotene was maximum in medium with NaNO3, Fe starvation increased the cellular abundance of C-phycocyanin and allophycocyanin by at least 22%. Compared to cells metabolizing NaNO3 and N2, cultures adapted to urea media increased their P, calcium and manganese demands by at least 72%, 97% and 76%, respectively. Variations on pigmentation and nutrient uptake were attributed to changes in phycocyanobilin biosynthesis, light-induced oxidation of carotenoids, and urea-promoted peroxidation. This work presents insights into developing optimal Anabaena culture for efficient operations of bioproduction and wastewater bioremediation with cyanobacteria.
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Wu G, Ma L, Sayre RT, Lee CH. Identification of the Optimal Light Harvesting Antenna Size for High-Light Stress Mitigation in Plants. FRONTIERS IN PLANT SCIENCE 2020; 11:505. [PMID: 32499795 PMCID: PMC7243658 DOI: 10.3389/fpls.2020.00505] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Accepted: 04/03/2020] [Indexed: 05/10/2023]
Abstract
One of the major constraints limiting biomass production in autotrophs is the low thermodynamic efficiency of photosynthesis, ranging from 1 to 4%. Given the absorption spectrum of photosynthetic pigments and the spectral distribution of sunlight, photosynthetic efficiencies as high as 11% are possible. It is well-recognized that the greatest thermodynamic inefficiencies in photosynthesis are associated with light absorption and conversion of excited states into chemical energy. This is due to the fact that photosynthesis light saturates at one quarter full sunlight intensity in plants resulting in the dissipation of excess energy as heat, fluorescence and through the production of damaging reactive oxygen species. Recently, it has been demonstrated that it is possible to adjust the size of the light harvesting antenna over a broad range of optical cross sections through targeted reductions in chlorophyll b content, selectively resulting in reductions of the peripheral light harvesting antenna size, especially in the content of Lhcb3 and Lhcb6. We have examined the impact of alterations in light harvesting antenna size on the amplitude of photoprotective activity and the evolutionary fitness or seed production in Camelina grown at super-saturating and sub-saturating light intensities to gain an understanding of the driving forces that lead to the selection for light harvesting antenna sizes best fit for a range of light intensities. We demonstrate that plants having light harvesting antenna sizes engineered for the greatest photosynthetic efficiency also have the greatest capacity to mitigate high light stress through non-photochemical quenching and reduction of reactive oxygen associated damage. Under sub-saturating growth light intensities, we demonstrate that the optimal light harvesting antenna size for photosynthesis and seed production is larger than that for plants grown at super-saturating light intensities and is more similar to the antenna size of wild-type plants. These results suggest that the light harvesting antenna size of plants is designed to maximize fitness under low light conditions such as occurs in shaded environments and in light competition with other plants.
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Affiliation(s)
- Guangxi Wu
- Department of Molecular Biology, Pusan National University, Busan, South Korea
- Pebble Labs, Los Alamos, NM, United States
- New Mexico Consortium, Los Alamos, NM, United States
| | - Lin Ma
- Department of Molecular Biology, Pusan National University, Busan, South Korea
- Pebble Labs, Los Alamos, NM, United States
- New Mexico Consortium, Los Alamos, NM, United States
| | - Richard T. Sayre
- Pebble Labs, Los Alamos, NM, United States
- New Mexico Consortium, Los Alamos, NM, United States
- *Correspondence: Richard T. Sayre,
| | - Choon-Hwan Lee
- Department of Molecular Biology, Pusan National University, Busan, South Korea
- Pebble Labs, Los Alamos, NM, United States
- New Mexico Consortium, Los Alamos, NM, United States
- Choon-Hwan Lee,
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Nazir F, Hussain A, Fariduddin Q. Hydrogen peroxide modulate photosynthesis and antioxidant systems in tomato (Solanum lycopersicum L.) plants under copper stress. CHEMOSPHERE 2019; 230:544-558. [PMID: 31125883 DOI: 10.1016/j.chemosphere.2019.05.001] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2018] [Revised: 04/09/2019] [Accepted: 05/01/2019] [Indexed: 05/23/2023]
Abstract
Plant growth and development could be modulated by minute concentrations of hydrogen peroxide (H2O2) which serves as a signaling molecule for various processes. The present work was conducted with an aim that H2O2 could also modify root morphology, morphology and movement of stomata, photosynthetic responses, activity of carbonic anhydrase, and antioxidant systems in tomato (Solanum lycopersicum L.) plants under copper stress (Cu; 10 or 100 mg kg-1 soil). Roots of 20 d old plants were dipped in 0.1 or 0.5 mM of H2O2 solution for 4 h and then transplanted to the soil filled in earthen pots. High Cu stress (100 mg kg-1 soil) altered root morphology, reduced chlorophyll content and photosynthetic capacity and also affected movement of stomata and generation of antioxidant species at 40 d after transplantation. Further, root dipping treatment of H2O2 to plants under stress and stress-free conditions enhanced accumulation of proline and activity of catalase, peroxidase, and superoxide dismutase, whereas production of superoxide radical (O2•¯) and H2O2 were decreased. Overall, H2O2 treatment improved growth, photosynthesis, metabolic state of the plants which provided tolerance and helped the plants to cope well under Cu stress.
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Affiliation(s)
- Faroza Nazir
- Plant Physiology and Biochemistry Section, Department of Botany, Faculty of Life Sciences, Aligarh Muslim University, Aligarh, 202002, India
| | - Anjuman Hussain
- Plant Physiology and Biochemistry Section, Department of Botany, Faculty of Life Sciences, Aligarh Muslim University, Aligarh, 202002, India
| | - Qazi Fariduddin
- Plant Physiology and Biochemistry Section, Department of Botany, Faculty of Life Sciences, Aligarh Muslim University, Aligarh, 202002, India.
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Borisova-Mubarakshina MM, Vetoshkina DV, Ivanov BN. Antioxidant and signaling functions of the plastoquinone pool in higher plants. PHYSIOLOGIA PLANTARUM 2019; 166:181-198. [PMID: 30706486 DOI: 10.1111/ppl.12936] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 01/23/2019] [Accepted: 01/25/2019] [Indexed: 05/25/2023]
Abstract
The review covers data representing the plastoquinone pool as the component integrated in plant antioxidant defense and plant signaling. The main goal of the review is to discuss the evidence describing the plastoquinone-involved biochemical reactions, which are incorporated in maintaining the sustainability of higher plants to stress conditions. In this context, the analysis of the reactions of various redox forms of plastoquinone with oxygen species is presented. The review describes how these reactions can constitute both the antioxidant and signaling functions of the pool. Special attention is paid to the reaction of superoxide anion radicals with plastohydroquinone molecules, producing hydrogen peroxide as signal molecules. Attention is also given to the processes affecting the redox state of the plastoquinone pool because the redox state of the pool is of special importance for antioxidant defense and signaling.
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Affiliation(s)
| | - Daria V Vetoshkina
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Pushchino, Russia
| | - Boris N Ivanov
- Institute of Basic Biological Problems of the Russian Academy of Sciences, Pushchino, Russia
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Nakamura M, Boussac A, Sugiura M. Consequences of structural modifications in cytochrome b 559 on the electron acceptor side of Photosystem II. PHOTOSYNTHESIS RESEARCH 2019; 139:475-486. [PMID: 29779191 DOI: 10.1007/s11120-018-0521-0] [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: 04/10/2018] [Accepted: 05/16/2018] [Indexed: 06/08/2023]
Abstract
Cytb559 in Photosystem II is a heterodimeric b-type cytochrome. The subunits, PsbE and PsbF, consist each in a membrane α-helix. Mutants were previously designed and studied in Thermosynechococcus elongatus (Sugiura et al., Biochim Biophys Acta 1847:276-285, 2015) either in which an axial histidine ligand of the haem-iron was substituted for a methionine, the PsbE/H23M mutant in which the haem was lacking, or in which the haem environment was modified, the PsbE/Y19F and PsbE/T26P mutants. All these mutants remained active showing that the haem has no structural role provided that PsbE and PsbF subunits are present. Here, we have carried on the characterization of these mutants. The following results were obtained: (i) the Y19F mutation hardly affect the Em of Cytb559, whereas the T26P mutation converts the haem into a form with a Em much below 0 mV (so low that it is likely not reducible by QB-) even in an active enzyme; (ii) in the PsbE/H23M mutant, and to a less extent in PsbE/T26P mutant, the electron transfer efficiency from QA- to QB is decreased; (iii) the lower Em of the QA/QA- couple in the PsbE/H23M mutant correlates with a higher production of singlet oxygen; (iv) the superoxide and/or hydroperoxide formation was not increased in the PsbE/H23M mutant lacking the haem, whereas it was significantly larger in the PsbE/T26P. These data are discussed in view of the literature to discriminate between structural and redox roles for the haem of Cytb559 in the production of reactive oxygen species.
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Affiliation(s)
- Makoto Nakamura
- Graduate School of Science and Technology, Ehime University, Bunkyo-cho, Matsuyama, Ehime, 790-8577, Japan
| | - Alain Boussac
- I2BC, CNRS UMR 9198, CEA Saclay, 91191, Gif-sur-Yvette, France
| | - Miwa Sugiura
- Graduate School of Science and Technology, Ehime University, Bunkyo-cho, Matsuyama, Ehime, 790-8577, Japan.
- Proteo-Science Research Center, Ehime University, Bunkyo-cho, Matsuyama, Ehime, 790-8577, Japan.
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Kosugi M, Maruo F, Inoue T, Kurosawa N, Kawamata A, Koike H, Kamei Y, Kudoh S, Imura S. A comparative study of wavelength-dependent photoinactivation in photosystem II of drought-tolerant photosynthetic organisms in Antarctica and the potential risks of photoinhibition in the habitat. ANNALS OF BOTANY 2018; 122:1263-1278. [PMID: 30052754 PMCID: PMC6324753 DOI: 10.1093/aob/mcy139] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Accepted: 07/16/2018] [Indexed: 05/22/2023]
Abstract
BACKGROUND AND AIMS All photosynthetic organisms are faced with photoinhibition, which would lead to death in severe environments. Because light quality and light intensity fluctuate dynamically in natural microenvironments, quantitative and qualitative analysis of photoinhibition is important to clarify how this environmental pressure has impacted ecological behaviour in different organisms. METHODS We evaluated the wavelength dependency of photoinactivation to photosystem II (PSII) of Prasiola crispa (green alga), Umbilicaria decussata (lichen) and Ceratodon purpureus (bryophyte) harvested from East Antarctica. For evaluation, we calculated reaction coefficients, Epis, of PSII photoinactivation against energy dose using a large spectrograph. Daily fluctuation of the rate coefficient of photoinactivation, kpi, was estimated from Epis and ambient light spectra measured during the summer season. KEY RESULTS Wavelength dependency of PSII photoinactivation was different for the three species, although they form colonies in close proximity to each other in Antarctica. The lichen exhibited substantial resistance to photoinactivation at all wavelengths, while the bryophyte showed sensitivity only to UV-B light (<325 nm). On the other hand, the green alga, P. crispa, showed ten times higher Epi to UV-B light than the bryophyte. It was much more sensitive to UV-A (325-400 nm). The risk of photoinhibition fluctuated considerably throughout the day. On the other hand, Epis were reduced dramatically for dehydrated compared with hydrated P. crispa. CONCLUSIONS The deduced rate coefficients of photoinactivation under ambient sunlight suggested that P. crispa needs to pay a greater cost to recover from photodamage than the lichen or the bryophyte in order to keep sufficient photosynthetic activity under the Antarctic habitat. A newly identified drought-induced protection mechanism appears to operate in P. crispa, and it plays a critical role in preventing the oxygen-evolving complex from photoinactivation when the repair cycle is inhibited by dehydration.
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Affiliation(s)
- Makiko Kosugi
- National Institute of Polar Research, Research Organization of Information and Systems, Tachikawa, Tokyo, Japan
- Department of Biological Sciences, Faculty of Science and Engineering, Chuo University, Bunkyo-ku, Tokyo, Japan
- For correspondence. E-mail:
| | - Fumino Maruo
- Department of Polar Science, School of Multidisciplinary Science, SOKENDAI (The Graduate University for Advanced Studies), Tachikawa, Tokyo, Japan
| | - Takeshi Inoue
- Department of Polar Science, School of Multidisciplinary Science, SOKENDAI (The Graduate University for Advanced Studies), Tachikawa, Tokyo, Japan
| | - Norio Kurosawa
- Department of Science and Engineering for Sustainable Innovation, Faculty of Science and Engineering, Soka University, Hachioji, Tokyo, Japan
| | - Akinori Kawamata
- Nature Research Group, Ehime Prefectural Science Museum, Ehime, Japan
| | - Hiroyuki Koike
- Department of Biological Sciences, Faculty of Science and Engineering, Chuo University, Bunkyo-ku, Tokyo, Japan
| | - Yasuhiro Kamei
- Department of Basic Biology, School of Life Sciences, SOKENDAI (The Graduate University for Advanced Studies), Myodaiji, Okazaki, Aichi, Japan
- National Institute for Basic Biology, National Institutes of Natural Sciences, Myodaiji, Okazaki, Japan
| | - Sakae Kudoh
- National Institute of Polar Research, Research Organization of Information and Systems, Tachikawa, Tokyo, Japan
- Department of Polar Science, School of Multidisciplinary Science, SOKENDAI (The Graduate University for Advanced Studies), Tachikawa, Tokyo, Japan
| | - Satoshi Imura
- National Institute of Polar Research, Research Organization of Information and Systems, Tachikawa, Tokyo, Japan
- Department of Polar Science, School of Multidisciplinary Science, SOKENDAI (The Graduate University for Advanced Studies), Tachikawa, Tokyo, Japan
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Hilgers EJA, Schöttler MA, Mettler-Altmann T, Krueger S, Dörmann P, Eicks M, Flügge UI, Häusler RE. The Combined Loss of Triose Phosphate and Xylulose 5-Phosphate/Phosphate Translocators Leads to Severe Growth Retardation and Impaired Photosynthesis in Arabidopsis thaliana tpt/xpt Double Mutants. FRONTIERS IN PLANT SCIENCE 2018; 9:1331. [PMID: 30333839 PMCID: PMC6175978 DOI: 10.3389/fpls.2018.01331] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2018] [Accepted: 08/24/2018] [Indexed: 05/18/2023]
Abstract
The xylulose 5-phosphate/phosphate translocator (XPT) represents the fourth functional member of the phosphate translocator (PT) family residing in the plastid inner envelope membrane. In contrast to the other three members, little is known on the physiological role of the XPT. Based on its major transport substrates (i.e., pentose phosphates) the XPT has been proposed to act as a link between the plastidial and extraplastidial branches of the oxidative pentose phosphate pathway (OPPP). As the XPT is also capable of transporting triose phosphates, it might as well support the triose phosphate PT (TPT) in exporting photoassimilates from the chloroplast in the light ('day path of carbon') and hence in supplying the whole plant with carbohydrates. Two independent knockout mutant alleles of the XPT (xpt-1 and xpt-2) lacked any specific phenotype, suggesting that the XPT function is redundant. However, double mutants generated from crossings of xpt-1 to different mutant alleles of the TPT (tpt-1 and tpt-2) were severely retarded in size, exhibited a high chlorophyll fluorescence phenotype, and impaired photosynthetic electron transport rates. In the double mutant the export of triose phosphates from the chloroplasts is completely blocked. Hence, precursors for sucrose biosynthesis derive entirely from starch turnover ('night path of carbon'), which was accompanied by a marked accumulation of maltose as a starch breakdown product. Moreover, pentose phosphates produced by the extraplastidial branch of the OPPP also accumulated in the double mutants. Thus, an active XPT indeed retrieves excessive pentose phosphates from the extra-plastidial space and makes them available to the plastids. Further metabolic profiling revealed that phosphorylated intermediates remained largely unaffected, whereas fumarate and glycine contents were diminished in the double mutants. The assessment of C/N-ratios suggested co-limitations of C- and N-metabolism as possible cause for growth retardation of the double mutants. Feeding of sucrose partially rescued the growth and photosynthesis phenotypes of the double mutants. Immunoblots of thylakoid proteins, spectroscopic determinations of photosynthesis complexes, and chlorophyll a fluorescence emission spectra at 77 Kelvin could only partially explain constrains in photosynthesis observed in the double mutants. The data are discussed together with aspects of the OPPP and central carbon metabolism.
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Affiliation(s)
- Elke J. A. Hilgers
- Department of Biology, Cologne Biocenter, Botanical Institute II and Cluster of Excellence on Plant Sciences, University of Cologne, Cologne, Germany
| | | | | | - Stephan Krueger
- Department of Biology, Cologne Biocenter, Botanical Institute II and Cluster of Excellence on Plant Sciences, University of Cologne, Cologne, Germany
| | - Peter Dörmann
- Molecular Biotechnology and Biochemistry, Universität Bonn, Bonn, Germany
| | | | - Ulf-Ingo Flügge
- Department of Biology, Cologne Biocenter, Botanical Institute II and Cluster of Excellence on Plant Sciences, University of Cologne, Cologne, Germany
| | - Rainer E. Häusler
- Department of Biology, Cologne Biocenter, Botanical Institute II and Cluster of Excellence on Plant Sciences, University of Cologne, Cologne, Germany
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Siddiqui H, Ahmed KBM, Hayat S. Comparative effect of 28-homobrassinolide and 24-epibrassinolide on the performance of different components influencing the photosynthetic machinery in Brassica juncea L. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2018; 129:198-212. [PMID: 29894860 DOI: 10.1016/j.plaphy.2018.05.027] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 05/26/2018] [Indexed: 05/11/2023]
Abstract
BRs are polyhydroxylated sterol derivatives, classified as phytohormones. Plants of Brassica juncea var. Varuna were grown in pots and an aqueous solution (10-8 M) of two brassinosteroid isomers 28-homobrassinolide (HBL) and 24-epibrassinolide (EBL) of same concentration (10-8 M) was applied to their leaves. The treatment up-regulated the photosynthetic machinery directly by enhancing water splitting activity, photochemical quenching, non-photochemical quenching, maximum PSII efficiency, actual PSII efficiency, electron transport rate, stomatal movement, stomatal conductance, internal CO2 concentration, transpiration rate, net photosynthetic rate and carbohydrate synthesis. Moreover, the level of biochemical enzymes (carbonic anhydrase and nitrate reductase), reactive oxygen species (superoxide and hydrogen peroxide) generation, antioxidant enzyme activity and mineral status (C, N, Mg, P, S, K), which indirectly influence the rate of photosynthesis, also improved in the treated plants. Out of the two BR analogues tested, EBL excelled in its effects over HBL.
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Affiliation(s)
- Husna Siddiqui
- Plant Physiology Section, Department of Botany, Aligarh Muslim University, Aligarh 202002, India
| | - Khan Bilal Mukhtar Ahmed
- Plant Physiology Section, Department of Botany, Aligarh Muslim University, Aligarh 202002, India
| | - Shamsul Hayat
- Plant Physiology Section, Department of Botany, Aligarh Muslim University, Aligarh 202002, India.
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Huang W, Tikkanen M, Zhang SB. Photoinhibition of photosystem I in Nephrolepis falciformis depends on reactive oxygen species generated in the chloroplast stroma. PHOTOSYNTHESIS RESEARCH 2018; 137:129-140. [PMID: 29357086 DOI: 10.1007/s11120-018-0484-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 01/17/2018] [Indexed: 05/26/2023]
Abstract
We studied how high light causes photoinhibition of photosystem I (PSI) in the shade-demanding fern Nephrolepis falciformis, in an attempt to understand the mechanism of PSI photoinhibition under natural field conditions. Intact leaves were treated with constant high light and fluctuating light. Detached leaves were treated with constant high light in the presence and absence of methyl viologen (MV). Chlorophyll fluorescence and P700 signal were determined to estimate photoinhibition. PSI was highly oxidized under high light before treatments. N. falciformis showed significantly stronger photoinhibition of PSI and PSII under constant high light than fluctuating light. These results suggest that high levels of P700 oxidation ratio cannot prevent PSI photoinhibition under high light in N. falciformis. Furthermore, photoinhibition of PSI in N. falciformis was largely accelerated in the presence of MV that promotes the production of superoxide anion radicals in the chloroplast stroma by accepting electrons from PSI. From these results, we propose that photoinhibition of PSI in N. falciformis is mainly caused by superoxide radicals generated in the chloroplast stroma, which is different from the mechanism of PSI photoinhibition in Arabidopsis thaliana and spinach. Here, we provide some new insights into the PSI photoinhibition under natural field conditions.
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Affiliation(s)
- Wei Huang
- Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, Yunnan, China
| | - Mikko Tikkanen
- Department of Biochemistry, Molecular Plant Biology, University of Turku, 20014, Turku, Finland
| | - Shi-Bao Zhang
- Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, Yunnan, China.
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Huang W, Yang YJ, Zhang JL, Hu H, Zhang SB. Superoxide generated in the chloroplast stroma causes photoinhibition of photosystem I in the shade-establishing tree species Psychotria henryi. PHOTOSYNTHESIS RESEARCH 2017; 132:293-303. [PMID: 28432538 DOI: 10.1007/s11120-017-0389-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Accepted: 04/15/2017] [Indexed: 05/07/2023]
Abstract
Our previous studies indicated that high light induced significant photoinhibition of photosystem I (PSI) in the shade-establishing tree species Psychotria henryi. However, the underlying mechanism has not been fully clarified. In the present study, in order to investigate the mechanism of PSI photoinhibition in P. henryi, we treated detached leaves with constant high light in the presence of methyl viologen (MV) or a soluble α-tocopherol analog, 2,2,5,7,8-pentamethyl-6-chromanol (PMC). We found that MV significantly depressed photochemical quantum yields in PSI and PSII when compared to PMC. On condition that no PSI photoinhibition happened, although cyclic electron flow (CEF) was abolished in the MV-treated samples, P700 oxidation ratio was maintain at higher levels than the PMC-treated samples. In the presence of PMC, PSI photoinhibition little changed but PSII photoinhibition was significantly alleviated. Importantly, PSI photoinhibition was largely accelerated in the presence of MV, which stimulates the production of superoxide and subsequently other reactive oxygen species at the chloroplast stroma by accepting electrons from PSI. Furthermore, MV largely aggravated PSII photoinhibition when compared to control. These results suggest that high P700 oxidation ratio cannot prevent PSI photoinhibition in P. henryi. Furthermore, the superoxide produced in the chloroplast stroma is critical for PSI photoinhibition in the higher plant P. henryi, which is opposite to the mechanism underlying PSI photoinhibition in Arabidopsis thaliana and spinach. These findings highlight a new mechanism of PSI photoinhibition in higher plants.
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Affiliation(s)
- Wei Huang
- Key Laboratory of Economic Plants and Biotechnology, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, Yunnan, China
- Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, 666303, Yunnan, China
| | - Ying-Jie Yang
- Key Laboratory of Economic Plants and Biotechnology, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, Yunnan, China
| | - Jiao-Lin Zhang
- Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, 666303, Yunnan, China
| | - Hong Hu
- Key Laboratory of Economic Plants and Biotechnology, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, Yunnan, China
| | - Shi-Bao Zhang
- Key Laboratory of Economic Plants and Biotechnology, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, Yunnan, China.
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Huang JY, Chiu YF, Ortega JM, Wang HT, Tseng TS, Ke SC, Roncel M, Chu HA. Mutations of Cytochrome b559 and PsbJ on and near the QC Site in Photosystem II Influence the Regulation of Short-Term Light Response and Photosynthetic Growth of the Cyanobacterium Synechocystis sp. PCC 6803. Biochemistry 2016; 55:2214-26. [DOI: 10.1021/acs.biochem.6b00133] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Jine-Yung Huang
- Institute
of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Yi-Fang Chiu
- Institute
of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - José M. Ortega
- Instituto
de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Avda. Américo Vespucio 49, 41092 Seville, Spain
| | - Hsing-Ting Wang
- Institute
of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Tien-Sheng Tseng
- Institute
of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Shyue-Chu Ke
- Department
of Physics, National Dong Hwa University, Hualien 97401, Taiwan
| | - Mercedes Roncel
- Instituto
de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Avda. Américo Vespucio 49, 41092 Seville, Spain
| | - Hsiu-An Chu
- Institute
of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
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Laisk A, Eichelmann H, Oja V. Oxidation of plastohydroquinone by photosystem II and by dioxygen in leaves. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2015; 1847:565-75. [PMID: 25800682 DOI: 10.1016/j.bbabio.2015.03.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 02/16/2015] [Accepted: 03/15/2015] [Indexed: 10/23/2022]
Abstract
In sunflower leaves linear electron flow LEF=4O2 evolution rate was measured at 20 ppm O2 in N2. PSII charge separation rate CSRII=aII∙PAD∙(Fm-F)/Fm, where aII is excitation partitioning to PSII, PAD is photon absorption density, Fm and F are maximum and actual fluorescence yields. Under 630 nm LED+720 nm far-red light (FRL), LEF was equal to CSRII with aII=0.51 to 0.58. After FRL was turned off, plastoquinol (PQH2) accumulated, but LEF decreased more than accountable by F increase, indicating PQH2-oxidizing cyclic electron flow in PSII (CEFII). CEFII was faster under conditions requiring more ATP, consistent with CEFII being coupled with proton translocation. We propose that PQH2 bound to the QC site is oxidized, one e- moving to P680+, the other e- to Cyt b559. From Cyt b559 the e- reduces QB- at the QB site, forming PQH2. About 10-15% electrons may cycle, causing misses in the period-4 flash O2 evolution and lower quantum yield of photosynthesis under stress. We also measured concentration dependence of PQH2 oxidation by dioxygen, as indicated by post-illumination decrease of Chl fluorescence yield. After light was turned off, F rapidly decreased from Fm to 0.2 Fv, but further decrease to F0 was slow and O2 concentration dependent. The rate constant of PQH2 oxidation, determined from this slow phase, was 0.054 s(-1) at 270 μM (21%) O2, decreasing with Km(O2) of 60 μM (4.6%) O2. This eliminates the interference of O2 in the measurements of CEFII.
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Affiliation(s)
- Agu Laisk
- Tartu Ülikooli Tehnoloogia Instituut, Nooruse tn. 1, Tartu 50411, Estonia.
| | - Hillar Eichelmann
- Tartu Ülikooli Tehnoloogia Instituut, Nooruse tn. 1, Tartu 50411, Estonia
| | - Vello Oja
- Tartu Ülikooli Tehnoloogia Instituut, Nooruse tn. 1, Tartu 50411, Estonia
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Chu HA, Chiu YF. The Roles of Cytochrome b 559 in Assembly and Photoprotection of Photosystem II Revealed by Site-Directed Mutagenesis Studies. FRONTIERS IN PLANT SCIENCE 2015; 6:1261. [PMID: 26793230 PMCID: PMC4709441 DOI: 10.3389/fpls.2015.01261] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 12/24/2015] [Indexed: 05/05/2023]
Abstract
Cytochrome b 559 (Cyt b 559) is one of the essential components of the Photosystem II reaction center (PSII). Despite recent accomplishments in understanding the structure and function of PSII, the exact physiological function of Cyt b 559 remains unclear. Cyt b 559 is not involved in the primary electron transfer pathway in PSII but may participate in secondary electron transfer pathways that protect PSII against photoinhibition. Site-directed mutagenesis studies combined with spectroscopic and functional analysis have been used to characterize Cyt b 559 mutant strains and their mutant PSII complex in higher plants, green algae, and cyanobacteria. These integrated studies have provided important in vivo evidence for possible physiological roles of Cyt b 559 in the assembly and stability of PSII, protecting PSII against photoinhibition, and modulating photosynthetic light harvesting. This mini-review presents an overview of recent important progress in site-directed mutagenesis studies of Cyt b 559 and implications for revealing the physiological functions of Cyt b 559 in PSII.
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Yadav DK, Prasad A, Kruk J, Pospíšil P. Evidence for the involvement of loosely bound plastosemiquinones in superoxide anion radical production in photosystem II. PLoS One 2014; 9:e115466. [PMID: 25541694 PMCID: PMC4277363 DOI: 10.1371/journal.pone.0115466] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 11/24/2014] [Indexed: 11/22/2022] Open
Abstract
Recent evidence has indicated the presence of novel plastoquinone-binding sites, QC and QD, in photosystem II (PSII). Here, we investigated the potential involvement of loosely bound plastosemiquinones in superoxide anion radical (O2•−) formation in spinach PSII membranes using electron paramagnetic resonance (EPR) spin-trapping spectroscopy. Illumination of PSII membranes in the presence of the spin trap EMPO (5-(ethoxycarbonyl)-5-methyl-1-pyrroline N-oxide) resulted in the formation of O2•−, which was monitored by the appearance of EMPO-OOH adduct EPR signal. Addition of exogenous short-chain plastoquinone to PSII membranes markedly enhanced the EMPO-OOH adduct EPR signal. Both in the unsupplemented and plastoquinone-supplemented PSII membranes, the EMPO-OOH adduct EPR signal was suppressed by 50% when the urea-type herbicide DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea) was bound at the QB site. However, the EMPO-OOH adduct EPR signal was enhanced by binding of the phenolic-type herbicide dinoseb (2,4-dinitro-6-sec-butylphenol) at the QD site. Both in the unsupplemented and plastoquinone-supplemented PSII membranes, DCMU and dinoseb inhibited photoreduction of the high-potential form of cytochrome b559 (cyt b559). Based on these results, we propose that O2•− is formed via the reduction of molecular oxygen by plastosemiquinones formed through one-electron reduction of plastoquinone at the QB site and one-electron oxidation of plastoquinol by cyt b559 at the QC site. On the contrary, the involvement of a plastosemiquinone formed via the one-electron oxidation of plastoquinol by cyt b559 at the QD site seems to be ambiguous. In spite of the fact that the existence of QC and QD sites is not generally accepted yet, the present study provided more spectroscopic data on the potential functional role of these new plastoquinone-binding sites.
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Affiliation(s)
- Deepak Kumar Yadav
- Department of Biophysics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Olomouc, Czech Republic
| | - Ankush Prasad
- Department of Biophysics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Olomouc, Czech Republic
| | - Jerzy Kruk
- Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Kraków, Poland
| | - Pavel Pospíšil
- Department of Biophysics, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, Olomouc, Czech Republic
- * E-mail:
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18
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Sugiura M, Nakamura M, Koyama K, Boussac A. Assembly of oxygen-evolving Photosystem II efficiently occurs with the apo-Cytb559 but the holo-Cytb559 accelerates the recovery of a functional enzyme upon photoinhibition. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1847:276-285. [PMID: 25481108 DOI: 10.1016/j.bbabio.2014.11.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Revised: 11/17/2014] [Accepted: 11/26/2014] [Indexed: 10/24/2022]
Abstract
Cytb559 in Photosystem II is a heterodimeric b-type cytochrome. The subunits, PsbE and PsbF, consist each in a membrane α-helix. Roles for Cytb559 remain elusive. In Thermosynechococcus elongatus, taking advantage of the robustness of the PSII variant with PsbA3 as the D1 subunit (WT*3), 4 mutants were designed hoping to get mutants nevertheless the obligatory phototrophy of this cyanobacterium. In two of them, an axial histidine ligand of the haem-iron was substituted for either a methionine, PsbE/H23M, which could be potentially a ligand or for an alanine, PsbE/H23A, which cannot. In the other mutants, PsbE/Y19F and PsbE/T26P, the environment around PsbE/H23 was expected to be modified. From EPR, MALDI-TOF and O2 evolution activity measurements, the following results were obtained: Whereas the PsbE/H23M and PsbE/H23A mutants assemble only an apo-Cytb559 the steady-state level of active PSII was comparable to that in WT*3. The lack of the haem or, in PsbE/T26P, conversion of the high-potential into a lower potential form, slowed-down the recovery rate of the O2 activity after high-light illumination but did not affect the photoinhibition rate. This resulted in the following order for the steady-state level of active PSII centers under high-light conditions: PsbE/H23M≈PsbE/H23A<< PsbE/Y19F≤PsbE/T26P≤WT*3. These data show i) that the haem has no structural role provided that PsbE and PsbF are present, ii) a lack of correlation between the rate of photoinhibition and the Em of the haem and iii) that the holo-Cytb559 favors the recovery of a functional enzyme upon photoinhibition.
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Affiliation(s)
- Miwa Sugiura
- Proteo-Science Research Center, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan; Department of Chemistry, Graduate School of Science and Technology, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan; PRESTO, Japan Science and Technology Agency (JST), 4-1-8, Honcho, Kawauchi, Saitama 332-0012, Japan.
| | - Makoto Nakamura
- Department of Chemistry, Graduate School of Science and Technology, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
| | - Kazumi Koyama
- Proteo-Science Research Center, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
| | - Alain Boussac
- iBiTec-S, CNRS UMR 8221, CEA Saclay, 91191 Gif-sur-Yvette, France.
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Kangasjärvi S, Tikkanen M, Durian G, Aro EM. Photosynthetic light reactions--an adjustable hub in basic production and plant immunity signaling. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2014; 81:128-34. [PMID: 24361390 DOI: 10.1016/j.plaphy.2013.12.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 12/03/2013] [Indexed: 05/09/2023]
Abstract
Photosynthetic efficiency is a key trait that influences the sustainable utilization of plants for energy and nutrition. By now, extensive research on photosynthetic processes has underscored important structural and functional relationships among photosynthetic thylakoid membrane protein complexes, and their roles in determining the productivity and stress resistance of plants. Photosystem II photoinhibition-repair cycle, for example, has arisen vital in protecting also Photosystem I against light-induced damage. Availability of highly sophisticated genetic, biochemical and biophysical tools has greatly expanded the catalog of components that carry out photoprotective functions in plants. On thylakoid membranes, these components encompass a network of overlapping systems that allow delicate regulation of linear and cyclic electron transfer pathways, balancing of excitation energy distribution between the two photosystems and dissipation of excess light energy in the antenna system as heat. An increasing number of reports indicate that the above mentioned mechanisms also mediate important functions in the regulation of biotic stress responses in plants. Particularly the handling of excitation energy in the light harvesting II antenna complexes appears central to plant immunity signaling. Comprehensive understanding of the underlying mechanisms and regulatory cross-talk, however, still remain elusive. This review highlights the current understanding of components that regulate the function of photosynthetic light reactions and directly or indirectly also modulate disease resistance in higher plants.
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Affiliation(s)
| | - Mikko Tikkanen
- Molecular Plant Biology, University of Turku, FI-20014 Turku, Finland
| | - Guido Durian
- Molecular Plant Biology, University of Turku, FI-20014 Turku, Finland
| | - Eva-Mari Aro
- Molecular Plant Biology, University of Turku, FI-20014 Turku, Finland.
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Hamilton ML, Franco E, Deák Z, Schlodder E, Vass I, Nixon PJ. Investigating the photoprotective role of cytochrome b-559 in photosystem II in a mutant with altered ligation of the haem. PLANT & CELL PHYSIOLOGY 2014; 55:1276-85. [PMID: 24850839 DOI: 10.1093/pcp/pcu070] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Despite many years of study, the physiological role of cytochrome b-559 (Cyt b-559) within the photosystem II (PSII) complex still remains unclear. Here we describe the analysis of a mutant of the green alga Chlamydomonas reinhardtii in which the His ligand to the haem, provided by the alpha subunit, has been replaced by a Cys residue. The mutant is unable to grow photoautotrophically but can assemble oxygen-evolving PSII supercomplexes to 15-20% of the levels found in the wild-type control. Haem is still detected in the isolated PSII supercomplexes but at sub-stoichiometric levels consistent with weaker binding to the mutated cytochrome. Analysis of PSII activity in cells indicates slowed electron transfer in the mutant between plastoquinones QA and QB. We show that PSII activity in the mutant is more sensitive to chronic photoinhibition than the WT control because of two effects: a faster rate of damage and an impaired PSII repair cycle at the level of synthesis and/or incorporation of D1 into PSII. We also demonstrate that Cyt b-559 plays a role during the critical stage of assembling the Mn4CaO5 cluster. Overall we conclude that Cyt b-559 optimises electron transfer on the acceptor side of PSII and plays physiologically important roles in the assembly, repair and maintenance of the complex.
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Affiliation(s)
- Mary L Hamilton
- Department of Life Sciences, Sir Ernst Chain Building-Wolfson Laboratories, Imperial College London, S. Kensington campus, London, SW7 2AZ, UKPresent address: Rothamsted Research, West Common, Harpenden, Hertfordshire, AL5 2JQ, UK
| | - Emanuel Franco
- Department of Life Sciences, Sir Ernst Chain Building-Wolfson Laboratories, Imperial College London, S. Kensington campus, London, SW7 2AZ, UK
| | - Zsuzsanna Deák
- Institute of Plant Biology, Biological Research Center of the Hungarian Academy of Sciences, H-6701 Szeged, Hungary
| | - Eberhard Schlodder
- Max-Volmer-Institut für Biophysikalische Chemie und Biochemie, Technische Universität Berlin, D-10623 Berlin, Germany
| | - Imre Vass
- Institute of Plant Biology, Biological Research Center of the Hungarian Academy of Sciences, H-6701 Szeged, Hungary
| | - Peter J Nixon
- Department of Life Sciences, Sir Ernst Chain Building-Wolfson Laboratories, Imperial College London, S. Kensington campus, London, SW7 2AZ, UK
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Pospíšil P. The Role of Metals in Production and Scavenging of Reactive Oxygen Species in Photosystem II. ACTA ACUST UNITED AC 2014; 55:1224-32. [DOI: 10.1093/pcp/pcu053] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Guerrero F, Zurita JL, Roncel M, Kirilovsky D, Ortega JM. The role of the high potential form of the cytochrome b559: Study of Thermosynechococcus elongatus mutants. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:908-19. [PMID: 24613347 DOI: 10.1016/j.bbabio.2014.02.024] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 02/21/2014] [Accepted: 02/26/2014] [Indexed: 10/25/2022]
Abstract
Cytochrome b559 is an essential component of the photosystem II reaction center in photosynthetic oxygen-evolving organisms, but its function still remains unclear. The use of photosystem II preparations from Thermosynechococcus elongatus of high integrity and activity allowed us to measure for the first time the influence of cytochrome b559 mutations on its midpoint redox potential and on the reduction of the cytochrome b559 by the plastoquinone pool (or QB). In this work, five mutants having a mutation in the α-subunit (I14A, I14S, R18S, I27A and I27T) and one in the β-subunit (F32Y) of cytochrome b559 have been investigated. All the mutations led to a destabilization of the high potential form of the cytochrome b559. The midpoint redox potential of the high potential form was significantly altered in the αR18S and αI27T mutant strains. The αR18S strain also showed a high sensitivity to photoinhibitory illumination and an altered oxidase activity. This was suggested by measurements of light induced oxidation and dark re-reduction of the cytochrome b559 showing that under conditions of a non-functional water oxidation system, once the cytochrome is oxidized by P680(+), the yield of its reduction by QB or the PQ pool was smaller and the kinetic slower in the αR18S mutant than in the wild-type strain. Thus, the extremely positive redox potential of the high potential form of cytochrome b559 could be necessary to ensure efficient oxidation of the PQ pool and to function as an electron reservoir replacing the water oxidation system when it is not operating.
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Affiliation(s)
- Fernando Guerrero
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Américo Vespucio 49, 41092 Seville, Spain; Laboratoire de Bioénergétique Moléculaire et Photosynthèse, Institut de Biologie et de Technologies de Saclay (iBiTec-S), CEA Saclay, 91191 Gif-sur-Yvette cedex, France.
| | - Jorge L Zurita
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Américo Vespucio 49, 41092 Seville, Spain; Laboratoire de Bioénergétique Moléculaire et Photosynthèse, Institut de Biologie et de Technologies de Saclay (iBiTec-S), CEA Saclay, 91191 Gif-sur-Yvette cedex, France.
| | - Mercedes Roncel
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Américo Vespucio 49, 41092 Seville, Spain.
| | - Diana Kirilovsky
- Laboratoire de Bioénergétique Moléculaire et Photosynthèse, Institut de Biologie et de Technologies de Saclay (iBiTec-S), CEA Saclay, 91191 Gif-sur-Yvette cedex, France.
| | - José M Ortega
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Américo Vespucio 49, 41092 Seville, Spain.
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Kaminskaya OP, Shuvalov VA. Towards an understanding of the nature of the redox forms of cytochrome b559 in photosystem II. DOKL BIOCHEM BIOPHYS 2013; 450:151-4. [PMID: 23824458 DOI: 10.1134/s1607672913030101] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2012] [Indexed: 11/23/2022]
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24
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Chiu YF, Chen YH, Roncel M, Dilbeck PL, Huang JY, Ke SC, Ortega JM, Burnap RL, Chu HA. Spectroscopic and functional characterization of cyanobacterium Synechocystis PCC 6803 mutants on the cytoplasmic-side of cytochrome b559 in photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1827:507-19. [PMID: 23399490 DOI: 10.1016/j.bbabio.2013.01.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2012] [Revised: 01/18/2013] [Accepted: 01/30/2013] [Indexed: 11/19/2022]
Abstract
We performed spectroscopic and functional characterization on cyanobacterium Synechocystis PCC6803 with mutations of charged residues of the cytoplasmic side of cytochrome (Cyt) b559 in photosystem II (PSII). All of the mutant cells grew photoautotrophically and assembled stable PSII. However, R7Eα, R17Eα and R17Lβ mutant cells grew significantly slower and were more susceptible to photoinhibition than wild-type cells. The adverse effects of the arginine mutations on the activity and the stability of PSII were in the following order (R17Lβ>R7Eα>R17Eα and R17Aα). All these arginine mutants exhibited normal period-four oscillation in oxygen yield. Thermoluminescence characteristics indicated a slight decrease in the stability of the S3QB(-)/S2QB(-) charge pairs in the R7Eα and R17Lβ mutant cells. R7Eα and R17Lβ PSII core complexes contained predominantly the low potential form of Cyt b559. EPR results indicated the displacement of one of the two axial ligands to the heme of Cyt b559 in R7Eα and R17Lβ mutant reaction centers. Our results demonstrate that the electrostatic interactions between these arginine residues and the heme propionates of Cyt b559 are important to the structure and redox properties of Cyt b559. In addition, the blue light-induced nonphotochemical quenching was significantly attenuated and its recovery was accelerated in the R7Lα and R17Lβ mutant cells. Furthermore, ultra performance liquid chromatography-mass spectrometry results showed that the PQ pool was more reduced in the R7Eα and R17Lβ mutant cells than wild-type cells in the dark. Our data support a functional role of Cyt b559 in protection of PSII under photoinhibition conditions in vivo.
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Affiliation(s)
- Yi-Fang Chiu
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 11529, Taiwan
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Kaminskaya OP, Shuvalov VA. Biphasic reduction of cytochrome b559 by plastoquinol in photosystem II membrane fragments: evidence for two types of cytochrome b559/plastoquinone redox equilibria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1827:471-83. [PMID: 23357332 DOI: 10.1016/j.bbabio.2013.01.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Revised: 01/14/2013] [Accepted: 01/16/2013] [Indexed: 10/27/2022]
Abstract
In photosystem II membrane fragments with oxidized cytochrome (Cyt) b559 reduction of Cyt b559 by plastoquinol formed in the membrane pool under illumination and by exogenous decylplastoquinol added in the dark was studied. Reduction of oxidized Cyt b559 by plastoquinols proceeds biphasically comprising a fast component with a rate constant higher than (10s)(-1), named phase I, followed by a slower dark reaction with a rate constant of (2.7min)(-1) at pH6.5, termed phase II. The extents of both components of Cyt b559 reduction increased with increasing concentrations of the quinols, with that, maximally a half of oxidized Cyt b559 can be photoreduced or chemically reduced in phase I at pH6.5. The photosystem II herbicide dinoseb but not 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) competed with the quinol reductant in phase I. The results reveal that the two components of the Cyt b559 redox reaction reflect two redox equilibria attaining in different time domains. One-electron redox equilibrium between oxidized Cyt b559 and the photosystem II-bound plastoquinol is established in phase I of Cyt b559 reduction. Phase II is attributed to equilibration of Cyt b559 redox forms with the quinone pool. The quinone site involved in phase I of Cyt b559 reduction is considered to be the site regulating the redox potential of Cyt b559 which can accommodate quinone, semiquinone and quinol forms. The properties of this site designated here as QD clearly suggest that it is distinct from the site QC found in the photosystem II crystal structure.
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Affiliation(s)
- Olga P Kaminskaya
- Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia.
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Tyystjärvi E. Photoinhibition of Photosystem II. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 300:243-303. [PMID: 23273864 DOI: 10.1016/b978-0-12-405210-9.00007-2] [Citation(s) in RCA: 146] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Photoinhibition of Photosystem II (PSII) is the light-induced loss of PSII electron-transfer activity. Although photoinhibition has been studied for a long time, there is no consensus about its mechanism. On one hand, production of singlet oxygen ((1)O(2)) by PSII has promoted models in which this reactive oxygen species (ROS) is considered to act as the agent of photoinhibitory damage. These chemistry-based models have often not taken into account the photophysical features of photoinhibition-like light response and action spectrum. On the other hand, models that reproduce these basic photophysical features of the reaction have not considered the importance of data about ROS. In this chapter, it is shown that the evidence behind the chemistry-based models and the photophysically oriented models can be brought together to build a mechanism that confirms with all types of experimental data. A working hypothesis is proposed, starting with inhibition of the manganese complex by light. Inability of the manganese complex to reduce the primary donor promotes recombination between the oxidized primary donor and Q(A), the first stable quinone acceptor of PSII. (1)O(2) production due to this recombination may inhibit protein synthesis or spread the photoinhibitory damage to another PSII center. The production of (1)O(2) is transient because loss of activity of the oxygen-evolving complex induces an increase in the redox potential of Q(A), which lowers (1)O(2) production.
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Affiliation(s)
- Esa Tyystjärvi
- Molecular Plant Biology, Department of Biochemistry and Food Chemistry, University of Turku, Turku, Finland.
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Bermúdez MÁ, Galmés J, Moreno I, Mullineaux PM, Gotor C, Romero LC. Photosynthetic adaptation to length of day is dependent on S-sulfocysteine synthase activity in the thylakoid lumen. PLANT PHYSIOLOGY 2012; 160:274-88. [PMID: 22829322 PMCID: PMC3440205 DOI: 10.1104/pp.112.201491] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Accepted: 07/20/2012] [Indexed: 05/20/2023]
Abstract
Arabidopsis (Arabidopsis thaliana) chloroplasts contain two O-acetyl-serine(thiol)lyase (OASTL) homologs, OAS-B, which is an authentic OASTL, and CS26, which has S-sulfocysteine synthase activity. In contrast with OAS-B, the loss of CS26 function resulted in dramatic phenotypic changes, which were dependent on the light treatment. We have performed a detailed characterization of the photosynthetic and chlorophyll fluorescence parameters in cs26 plants compared with those of wild-type plants under short-day growth conditions (SD) and long-day growth conditions (LD). Under LD, the photosynthetic characterization, which was based on substomatal CO(2) concentrations and CO(2) concentration in the chloroplast curves, revealed significant reductions in most of the photosynthetic parameters for cs26, which were unchanged under SD. These parameters included net CO(2) assimilation rate, mesophyll conductance, and mitochondrial respiration at darkness. The analysis also showed that cs26 under LD required more absorbed quanta per driven electron flux and fixed CO(2). The nonphotochemical quenching values suggested that in cs26 plants, the excess electrons that are not used in photochemical reactions may form reactive oxygen species. A photoinhibitory effect was confirmed by the background fluorescence signal values under LD and SD, which were higher in young leaves compared with mature ones under SD. To hypothesize the role of CS26 in relation to the photosynthetic machinery, we addressed its location inside of the chloroplast. The activity determination and localization analyses that were performed using immunoblotting indicated the presence of an active CS26 enzyme exclusively in the thylakoid lumen. This finding was reinforced by the observation of marked alterations in many lumenal proteins in the cs26 mutant compared with the wild type.
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Schmitz J, Schöttler MA, Krueger S, Geimer S, Schneider A, Kleine T, Leister D, Bell K, Flügge UI, Häusler RE. Defects in leaf carbohydrate metabolism compromise acclimation to high light and lead to a high chlorophyll fluorescence phenotype in Arabidopsis thaliana. BMC PLANT BIOLOGY 2012; 12:8. [PMID: 22248311 PMCID: PMC3353854 DOI: 10.1186/1471-2229-12-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Accepted: 01/16/2012] [Indexed: 05/18/2023]
Abstract
BACKGROUND We have studied the impact of carbohydrate-starvation on the acclimation response to high light using Arabidopsis thaliana double mutants strongly impaired in the day- and night path of photoassimilate export from the chloroplast. A complete knock-out mutant of the triose phosphate/phosphate translocator (TPT; tpt-2 mutant) was crossed to mutants defective in (i) starch biosynthesis (adg1-1, pgm1 and pgi1-1; knock-outs of ADP-glucose pyrophosphorylase, plastidial phosphoglucomutase and phosphoglucose isomerase) or (ii) starch mobilization (sex1-3, knock-out of glucan water dikinase) as well as in (iii) maltose export from the chloroplast (mex1-2). RESULTS All double mutants were viable and indistinguishable from the wild type when grown under low light conditions, but--except for sex1-3/tpt-2--developed a high chlorophyll fluorescence (HCF) phenotype and growth retardation when grown in high light. Immunoblots of thylakoid proteins, Blue-Native gel electrophoresis and chlorophyll fluorescence emission analyses at 77 Kelvin with the adg1-1/tpt-2 double mutant revealed that HCF was linked to a specific decrease in plastome-encoded core proteins of both photosystems (with the exception of the PSII component cytochrome b559), whereas nuclear-encoded antennae (LHCs) accumulated normally, but were predominantly not attached to their photosystems. Uncoupled antennae are the major cause for HCF of dark-adapted plants. Feeding of sucrose or glucose to high light-grown adg1-1/tpt-2 plants rescued the HCF- and growth phenotypes. Elevated sugar levels induce the expression of the glucose-6-phosphate/phosphate translocator2 (GPT2), which in principle could compensate for the deficiency in the TPT. A triple mutant with an additional defect in GPT2 (adg1-1/tpt-2/gpt2-1) exhibited an identical rescue of the HCF- and growth phenotype in response to sugar feeding as the adg1-1/tpt-2 double mutant, indicating that this rescue is independent from the sugar-triggered induction of GPT2. CONCLUSIONS We propose that cytosolic carbohydrate availability modulates acclimation to high light in A. thaliana. It is conceivable that the strong relationship between the chloroplast and nucleus with respect to a co-ordinated expression of photosynthesis genes is modified in carbohydrate-starved plants. Hence carbohydrates may be considered as a novel component involved in chloroplast-to-nucleus retrograde signaling, an aspect that will be addressed in future studies.
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Affiliation(s)
- Jessica Schmitz
- University of Cologne, Botanical Institute, Biocenter Cologne, Zülpicher Str. 47B, D-50674 Cologne, Germany
| | - Mark Aurel Schöttler
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, D-14476 Potsdam-Golm, Germany
| | - Stephan Krueger
- University of Cologne, Botanical Institute, Biocenter Cologne, Zülpicher Str. 47B, D-50674 Cologne, Germany
| | - Stefan Geimer
- Universität Bayreuth, Zellbiologie/Elektronenmikroskopie NW I/B1, Universitätsstrasse 30, D-95447 Bayreuth, Germany
| | - Anja Schneider
- Biozentrum der Ludwig-Maximilians-Universität München, Department Biologie I - Botanik Großhaderner Str. 2-4, D-82152 Planegg-Martinsried, Germany
| | - Tatjana Kleine
- Biozentrum der Ludwig-Maximilians-Universität München, Department Biologie I - Botanik Großhaderner Str. 2-4, D-82152 Planegg-Martinsried, Germany
| | - Dario Leister
- Biozentrum der Ludwig-Maximilians-Universität München, Department Biologie I - Botanik Großhaderner Str. 2-4, D-82152 Planegg-Martinsried, Germany
| | - Kirsten Bell
- University of Cologne, Botanical Institute, Biocenter Cologne, Zülpicher Str. 47B, D-50674 Cologne, Germany
| | - Ulf-Ingo Flügge
- University of Cologne, Botanical Institute, Biocenter Cologne, Zülpicher Str. 47B, D-50674 Cologne, Germany
| | - Rainer E Häusler
- University of Cologne, Botanical Institute, Biocenter Cologne, Zülpicher Str. 47B, D-50674 Cologne, Germany
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Pure forms of the singlet oxygen sensors TEMP and TEMPD do not inhibit Photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:1658-61. [DOI: 10.1016/j.bbabio.2011.09.009] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2011] [Revised: 09/06/2011] [Accepted: 09/14/2011] [Indexed: 11/18/2022]
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Karamoko M, Cline S, Redding K, Ruiz N, Hamel PP. Lumen Thiol Oxidoreductase1, a disulfide bond-forming catalyst, is required for the assembly of photosystem II in Arabidopsis. THE PLANT CELL 2011; 23:4462-75. [PMID: 22209765 PMCID: PMC3269877 DOI: 10.1105/tpc.111.089680] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Revised: 11/15/2011] [Accepted: 12/13/2011] [Indexed: 05/18/2023]
Abstract
Here, we identify Arabidopsis thaliana Lumen Thiol Oxidoreductase1 (LTO1) as a disulfide bond-forming enzyme in the thylakoid lumen. Using topological reporters in bacteria, we deduced a lumenal location for the redox active domains of the protein. LTO1 can partially substitute for the proteins catalyzing disulfide bond formation in the bacterial periplasm, which is topologically equivalent to the plastid lumen. An insertional mutation within the LTO1 promoter is associated with a severe photoautotrophic growth defect. Measurements of the photosynthetic activity indicate that the lto1 mutant displays a limitation in the electron flow from photosystem II (PSII). In accordance with these measurements, we noted a severe depletion of the structural subunits of PSII but no change in the accumulation of the cytochrome b(6)f complex or photosystem I. In a yeast two-hybrid assay, the thioredoxin-like domain of LTO1 interacts with PsbO, a lumenal PSII subunit known to be disulfide bonded, and a recombinant form of the molecule can introduce a disulfide bond in PsbO in vitro. The documentation of a sulfhydryl-oxidizing activity in the thylakoid lumen further underscores the importance of catalyzed thiol-disulfide chemistry for the biogenesis of the thylakoid compartment.
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Affiliation(s)
- Mohamed Karamoko
- Department of Molecular Genetics and Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio 43210
| | - Sara Cline
- Department of Molecular Genetics and Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio 43210
- Plant Cellular and Molecular Biology Graduate Program, The Ohio State University, Columbus, Ohio 43210
| | - Kevin Redding
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287
| | - Natividad Ruiz
- Department of Microbiology, The Ohio State University, Columbus, Ohio 43210
| | - Patrice P. Hamel
- Department of Molecular Genetics and Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio 43210
- Plant Cellular and Molecular Biology Graduate Program, The Ohio State University, Columbus, Ohio 43210
- Address correspondence to
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31
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Shinopoulos KE, Brudvig GW. Cytochrome b₅₅₉ and cyclic electron transfer within photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:66-75. [PMID: 21864501 DOI: 10.1016/j.bbabio.2011.08.002] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Revised: 08/06/2011] [Accepted: 08/08/2011] [Indexed: 11/18/2022]
Abstract
Cytochrome b₅₅₉ (Cyt b₅₅₉), β-carotene (Car), and chlorophyll (Chl) cofactors participate in the secondary electron-transfer pathways in photosystem II (PSII), which are believed to protect PSII from photodamage under conditions in which the primary electron-donation pathway leading to water oxidation is inhibited. Among these cofactors, Cyt b₅₅₉ is preferentially photooxidized under conditions in which the primary electron-donation pathway is blocked. When Cyt b₅₅₉ is preoxidized, the photooxidation of several of the 11 Car and 35 Chl molecules present per PSII is observed. In this review, the discovery of the secondary electron donors, their structures and electron-transfer properties, and progress in the characterization of the secondary electron-transfer pathways are discussed. This article is part of a Special Issue entitled: Photosystem II.
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Cardona T, Sedoud A, Cox N, Rutherford AW. Charge separation in photosystem II: a comparative and evolutionary overview. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:26-43. [PMID: 21835158 DOI: 10.1016/j.bbabio.2011.07.012] [Citation(s) in RCA: 245] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Revised: 07/22/2011] [Accepted: 07/23/2011] [Indexed: 10/17/2022]
Abstract
Our current understanding of the PSII reaction centre owes a great deal to comparisons to the simpler and better understood, purple bacterial reaction centre. Here we provide an overview of the similarities with a focus on charge separation and the electron acceptors. We go on to discuss some of the main differences between the two kinds of reaction centres that have been highlighted by the improving knowledge of PSII. We attempt to relate these differences to functional requirements of water splitting. Some are directly associated with that function, e.g. high oxidation potentials, while others are associated with regulation and protection against photodamage. The protective and regulatory functions are associated with the harsh chemistry performed during its normal function but also with requirements of the enzyme while it is undergoing assembly and repair. Key aspects of PSII reaction centre evolution are also addressed. This article is part of a Special Issue entitled: Photosystem II.
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Affiliation(s)
- Tanai Cardona
- Institut de Biologie et Technologies de Saclay, URA 2096 CNRS, CEA Saclay, 91191 Gif-sur-Yvette, France
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Enzymatic function of cytochrome b559 in photosystem II. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2011; 104:341-7. [DOI: 10.1016/j.jphotobiol.2011.02.013] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2010] [Revised: 02/10/2011] [Accepted: 02/11/2011] [Indexed: 11/22/2022]
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Müh F, Glöckner C, Hellmich J, Zouni A. Light-induced quinone reduction in photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:44-65. [PMID: 21679684 DOI: 10.1016/j.bbabio.2011.05.021] [Citation(s) in RCA: 163] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Revised: 05/20/2011] [Accepted: 05/23/2011] [Indexed: 10/18/2022]
Abstract
The photosystem II core complex is the water:plastoquinone oxidoreductase of oxygenic photosynthesis situated in the thylakoid membrane of cyanobacteria, algae and plants. It catalyzes the light-induced transfer of electrons from water to plastoquinone accompanied by the net transport of protons from the cytoplasm (stroma) to the lumen, the production of molecular oxygen and the release of plastoquinol into the membrane phase. In this review, we outline our present knowledge about the "acceptor side" of the photosystem II core complex covering the reaction center with focus on the primary (Q(A)) and secondary (Q(B)) quinones situated around the non-heme iron with bound (bi)carbonate and a comparison with the reaction center of purple bacteria. Related topics addressed are quinone diffusion channels for plastoquinone/plastoquinol exchange, the newly discovered third quinone Q(C), the relevance of lipids, the interactions of quinones with the still enigmatic cytochrome b559 and the role of Q(A) in photoinhibition and photoprotection mechanisms. This article is part of a Special Issue entitled: Photosystem II.
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Affiliation(s)
- Frank Müh
- Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, D-10623 Berlin, Germany
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Ohad I, Raanan H, Keren N, Tchernov D, Kaplan A. Light-induced changes within photosystem II protects Microcoleus sp. in biological desert sand crusts against excess light. PLoS One 2010; 5:e11000. [PMID: 20544016 PMCID: PMC2882322 DOI: 10.1371/journal.pone.0011000] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2010] [Accepted: 05/16/2010] [Indexed: 12/16/2022] Open
Abstract
The filamentous cyanobacterium Microcoleus vaginatus, a major primary producer in desert biological sand crusts, is exposed to frequent hydration (by early morning dew) followed by desiccation during potentially damaging excess light conditions. Nevertheless, its photosynthetic machinery is hardly affected by high light, unlike “model” organisms whereby light-induced oxidative stress leads to photoinactivation of the oxygen-evolving photosystem II (PSII). Field experiments showed a dramatic decline in the fluorescence yield with rising light intensity in both drying and artificially maintained wet plots. Laboratory experiments showed that, contrary to “model” organisms, photosynthesis persists in Microcoleus sp. even at light intensities 2–3 times higher than required to saturate oxygen evolution. This is despite an extensive loss (85–90%) of variable fluorescence and thermoluminescence, representing radiative PSII charge recombination that promotes the generation of damaging singlet oxygen. Light induced loss of variable fluorescence is not inhibited by the electron transfer inhibitors 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 2,5-dibromo-3-methyl-6-isopropylbenzoquinone (DBMIB), nor the uncoupler carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP), thus indicating that reduction of plastoquinone or O2, or lumen acidification essential for non-photochemical quenching (NPQ) are not involved. The rate of QA− re-oxidation in the presence of DCMU is enhanced with time and intensity of illumination. The difference in temperatures required for maximal thermoluminescence emissions from S2/QA− (Q band, 22°C) and S2,3/QB− (B band, 25°C) charge recombinations is considerably smaller in Microcoleus as compared to “model” photosynthetic organisms, thus indicating a significant alteration of the S2/QA− redox potential. We propose that enhancement of non-radiative charge recombination with rising light intensity may reduce harmful radiative recombination events thereby lowering 1O2 generation and oxidative photodamage under excess illumination. This effective photo-protective mechanism was apparently lost during the evolution from the ancestor cyanobacteria to the higher plant chloroplast.
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Affiliation(s)
- Itzhak Ohad
- Department of Biological Chemistry, The Hebrew University of Jerusalem, Jerusalem, Irael
| | - Hagai Raanan
- Department of Plant and Environmental Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Nir Keren
- Department of Plant and Environmental Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Dan Tchernov
- The Interuniversity Institute for Marine Sciences in Eilat, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Aaron Kaplan
- Department of Plant and Environmental Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
- * E-mail:
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