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Toshiharu Shikanai - One of the best experts on this subject based on the ideXlab platform.
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physiological functions of cyclic electron transport around Photosystem i in sustaining photosynthesis and plant growth
Annual Review of Plant Biology, 2016Co-Authors: Wataru Yamori, Toshiharu ShikanaiAbstract:The light reactions in photosynthesis drive both linear and cyclic electron transport around Photosystem I (PSI). Linear electron transport generates both ATP and NADPH, whereas PSI cyclic electron transport produces ATP without producing NADPH. PSI cyclic electron transport is thought to be essential for balancing the ATP/NADPH production ratio and for protecting both Photosystems from damage caused by stromal overreduction. Two distinct pathways of cyclic electron transport have been proposed in angiosperms: a major pathway that depends on the PROTON GRADIENT REGULATION 5 (PGR5) and PGR5-LIKE PHOTOSYNTHETIC PHENOTYPE 1 (PGRL1) proteins, which are the target site of antimycin A, and a minor pathway mediated by the chloroplast NADH dehydrogenase–like (NDH) complex. Recently, the regulation of PSI cyclic electron transport has been recognized as essential for photosynthesis and plant growth. In this review, we summarize the possible functions and importance of the two pathways of PSI cyclic electron transport.
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cyclic electron flow around Photosystem i is essential for photosynthesis
Nature, 2004Co-Authors: Yuri Munekage, Mihoko Hashimoto, Chikahiro Miyake, Kenichi Tomizawa, Tsuyoshi Endo, Masao Tasaka, Toshiharu ShikanaiAbstract:Photosynthesis provides at least two routes through which light energy can be used to generate a proton gradient across the thylakoid membrane of chloroplasts, which is subsequently used to synthesize ATP. In the first route, electrons released from water in Photosystem II (PSII) are eventually transferred to NADP+ by way of Photosystem I (PSI)1. This linear electron flow is driven by two photochemical reactions that function in series. The cytochrome b6f complex mediates electron transport between the two Photosystems and generates the proton gradient (ΔpH). In the second route, driven solely by PSI, electrons can be recycled from either reduced ferredoxin or NADPH to plastoquinone, and subsequently to the cytochrome b6f complex2,3,4,5. Such cyclic flow generates ΔpH and thus ATP without the accumulation of reduced species. Whereas linear flow from water to NADP+ is commonly used to explain the function of the light-dependent reactions of photosynthesis, the role of cyclic flow is less clear. In higher plants cyclic flow consists of two partially redundant pathways. Here we have constructed mutants in Arabidopsis thaliana in which both PSI cyclic pathways are impaired, and present evidence that cyclic flow is essential for efficient photosynthesis.
Diana Kirilovsky - One of the best experts on this subject based on the ideXlab platform.
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State transitions in cyanobacteria studied with picosecond fluorescence at room temperature
Biochimica biophysica acta (BBA) - Bioenergetics, 2020Co-Authors: Ahmad Farhan Bhatti, Diana Kirilovsky, Reza Ranjbar Choubeh, Emilie Wientjes, Herbert Van AmerongenAbstract:Cyanobacteria can rapidly regulate the relative activity of their photosynthetic complexes Photosystem I and II (PSI and PSII) in response to changes in the illumination conditions. This process is known as state transitions. If PSI is preferentially excited, they go to state I whereas state II is induced either after preferential excitation of PSII or after dark adaptation. Different underlying mechanisms have been proposed in literature, in particular i) reversible shuttling of the external antenna complexes, the phycobilisomes, between PSI and PSII, ii) reversible spillover of excitation energy from PSII to PSI, iii) a combination of both and, iv) increased excited-state quenching of the PSII core in state II. Here we investigated wild-type and mutant strains of Synechococcus sp. PCC 7942 and Synechocystis sp. PCC 6803 using time-resolved fluorescence spectroscopy at room temperature. Our observations support model iv, meaning that increased excited-state quenching of the PSII core occurs in state II thereby balancing the photochemistry of Photosystems I and II.
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Different roles for ApcD and ApcF in Synechococcus elongatus and Synechocystis sp. PCC 6803 phycobilisomes
Biochimica biophysica acta (BBA) - Bioenergetics, 2019Co-Authors: Pablo I. Calzadilla, Fernando Muzzopappa, Pierre Sétif, Diana KirilovskyAbstract:The phycobilisome, the cyanobacterial light harvesting complex, is a huge phycobiliprotein containing extramembrane complex, formed by a core from which rods radiate. The phycobilisome has evolved to efficiently absorb sun energy and transfer it to the Photosystems via the last energy acceptors of the phycobilisome, ApcD and ApcE. ApcF also affects energy transfer by interacting with ApcE. In this work we studied the role of ApcD and ApcF in energy transfer and state transitions in Synechococcus elongatus and Synechocystis PCC6803. Our results demonstrate that these proteins have different roles in both processes in the two strains. The lack of ApcD and ApcF inhibits state transitions in Synechocystis but not in S. elongatus. In addition, lack of ApcF decreases energy transfer to both Photosystems only in Synechocystis, while the lack of ApcD alters energy transfer to Photosystem I only in S. elongatus. Thus, conclusions based on results obtained in one cyanobacterial strain cannot be systematically transferred to other strains and the putative role(s) of phycobilisomes in state transitions need to be reconsidered.
Herbert Van Amerongen - One of the best experts on this subject based on the ideXlab platform.
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State transitions in cyanobacteria studied with picosecond fluorescence at room temperature
Biochimica biophysica acta (BBA) - Bioenergetics, 2020Co-Authors: Ahmad Farhan Bhatti, Diana Kirilovsky, Reza Ranjbar Choubeh, Emilie Wientjes, Herbert Van AmerongenAbstract:Cyanobacteria can rapidly regulate the relative activity of their photosynthetic complexes Photosystem I and II (PSI and PSII) in response to changes in the illumination conditions. This process is known as state transitions. If PSI is preferentially excited, they go to state I whereas state II is induced either after preferential excitation of PSII or after dark adaptation. Different underlying mechanisms have been proposed in literature, in particular i) reversible shuttling of the external antenna complexes, the phycobilisomes, between PSI and PSII, ii) reversible spillover of excitation energy from PSII to PSI, iii) a combination of both and, iv) increased excited-state quenching of the PSII core in state II. Here we investigated wild-type and mutant strains of Synechococcus sp. PCC 7942 and Synechocystis sp. PCC 6803 using time-resolved fluorescence spectroscopy at room temperature. Our observations support model iv, meaning that increased excited-state quenching of the PSII core occurs in state II thereby balancing the photochemistry of Photosystems I and II.
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State transitions in Chlamydomonas reinhardtii strongly modulate the functional size of Photosystem II but not of Photosystem I.
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Caner Ünlü, Bartlomiej Drop, Roberta Croce, Herbert Van AmerongenAbstract:Plants and green algae optimize photosynthesis in changing light conditions by balancing the amount of light absorbed by Photosystems I and II. These Photosystems work in series to extract electrons from water and reduce NADP+ to NADPH. Light-harvesting complexes (LHCs) are held responsible for maintaining the balance by moving from one Photosystem to the other in a process called state transitions. In the green alga Chlamydomonas reinhardtii, a photosynthetic model organism, state transitions are thought to involve 80% of the LHCs. Here, we demonstrate with picosecond-fluorescence spectroscopy on C. reinhardtii cells that, although LHCs indeed detach from Photosystem II in state 2 conditions, only a fraction attaches to Photosystem I. The detached antenna complexes become protected against photodamage via shortening of the excited-state lifetime. It is discussed how the transition from state 1 to state 2 can protect C. reinhardtii in high-light conditions and how this differs from the situation in plants.
Jurgen Marquardt - One of the best experts on this subject based on the ideXlab platform.
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biochemical and immunochemical investigations on the light harvesting system of the cryptophyte rhodomonas sp evidence for a Photosystem i specific antenna
Plant Biology, 1999Co-Authors: L Bathke, Erhard Rhiel, Wolfgang E. Krumbein, Jurgen MarquardtAbstract:: Thylakoid membranes of the cryptophyte Rhodomonas sp. were solubilized with the mild detergent dodecyl-β-maltoside and subjected to sucrose density gradient centrifugation. The resulting gradients showed six pigment-bearing bands which were characterized further by means of absorption and fluorescence emission (77K) spectroscopy, polyacrylamide gel electrophoresis and Western immunoblotting. Two of the bands showed characteristics of light-harvesting complexes, other bands could be attributed to Photosystem II and Photosystem I. Up to 10 different light-harvesting proteins could be identified, some of which are specific for Photosystem I, others for Photosystem II. The polypeptides of the light-harvesting complex of Photosystem II show a higher chlorophyll c/a ratio than the antenna proteins of Photosystem I. As in vascular plants, they represent the bulk of the membrane-intrinsic light-harvesting proteins.
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Biochemical and Immunochemical Investigations on the Light‐Harvesting System of the Cryptophyte Rhodomonas sp.: Evidence for a Photosystem I Specific Antenna
Plant Biology, 1999Co-Authors: L Bathke, Erhard Rhiel, Wolfgang E. Krumbein, Jurgen MarquardtAbstract:: Thylakoid membranes of the cryptophyte Rhodomonas sp. were solubilized with the mild detergent dodecyl-β-maltoside and subjected to sucrose density gradient centrifugation. The resulting gradients showed six pigment-bearing bands which were characterized further by means of absorption and fluorescence emission (77K) spectroscopy, polyacrylamide gel electrophoresis and Western immunoblotting. Two of the bands showed characteristics of light-harvesting complexes, other bands could be attributed to Photosystem II and Photosystem I. Up to 10 different light-harvesting proteins could be identified, some of which are specific for Photosystem I, others for Photosystem II. The polypeptides of the light-harvesting complex of Photosystem II show a higher chlorophyll c/a ratio than the antenna proteins of Photosystem I. As in vascular plants, they represent the bulk of the membrane-intrinsic light-harvesting proteins.
Norbert Krauss - One of the best experts on this subject based on the ideXlab platform.
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Functional implications on the mechanism of the function of Photosystem II including water oxidation based on the structure of Photosystem II
Philosophical Transactions of the Royal Society B, 2002Co-Authors: Petra Fromme, Jaceck Biesiadka, Horst Tobias Witt, Jan Kern, Bernhard Loll, Wolfram Saenger, Norbert Krauss, Athina ZouniAbstract:The structure of Photosystem I at 3.8 A resolution illustrated the main structural elements of the water-oxidizing Photosystem II complex, including the constituents of the electron transport chain. The location of the Mn cluster within the complex has been identified for the first time to our knowledge. At this resolution, no individual atoms are visible, however, the electron density of the Mn cluster can be used to discuss both the present models of the Mn cluster as revealed from various spectroscopic methods and the implications for the mechanisms of water oxidation. Twenty-six chlorophylls from the antenna system of Photosystem II have been identified. They are arranged in two layers, one close to the stromal side and one close to the lumenal side. Comparing the structure of the antenna system of Photosystem II with the chlorophyll arrangement in Photosystem I, which was recently determined at 2.5 A resolution shows that Photosystem II lacks the central domain of the Photosystem I antenna, which is discussed in respect of the repair cycle of Photosystem II due to photoinhibition.
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Structure of Photosystem I.
Biochimica et Biophysica Acta, 2001Co-Authors: Petra Fromme, Patrick Jordan, Norbert KraussAbstract:In plants and cyanobacteria, the primary step in oxygenic photosynthesis, the light induced charge separation, is driven by two large membrane intrinsic protein complexes, the Photosystems I and II. Photosystem I catalyses the light driven electron transfer from plastocyanin/cytochrome c6 on the lumenal side of the membrane to ferredoxin/flavodoxin at the stromal side by a chain of electron carriers. Photosystem I of Synechococcus elongatus consists of 12 protein subunits, 96 chlorophyll a molecules, 22 carotenoids, three [4Fe4S] clusters and two phylloquinones. Furthermore, it has been discovered that four lipids are intrinsic components of Photosystem I. Photosystem I exists as a trimer in the native membrane with a molecular mass of 1068 kDa for the whole complex. The X-ray structure of Photosystem I at a resolution of 2.5 A O shows the location of the individual subunits and cofactors and provides new information on the protein^cofactor interactions. [P. Jordan, P. Fromme, H.T. Witt, O. Klukas, W. Saenger, N. KrauM, Nature 411 (2001) 909-917]. In this review, biochemical data and results of biophysical investigations are discussed with respect to the X-ray crystallographic structure in order to give an overview of the structure and function of this large membrane protein. fl 2001 Published by Elsevier Science B.V.
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three dimensional structure of cyanobacterial Photosystem i at 2 5 a resolution
Nature, 2001Co-Authors: Patrick Jordan, Petra Fromme, Wolfram Saenger, Norbert Krauss, Horst Toblas Witt, Olaf KlukasAbstract:Life on Earth depends on photosynthesis, the conversion of light energy from the Sun to chemical energy. In plants, green algae and cyanobacteria, this process is driven by the cooperation of two large protein-cofactor complexes, Photosystems I and II, which are located in the thylakoid photosynthetic membranes. The crystal structure of Photosystem I from the thermophilic cyanobacterium Synechococcus elongatus described here provides a picture at atomic detail of 12 protein subunits and 127 cofactors comprising 96 chlorophylls, 2 phylloquinones, 3 Fe4S4 clusters, 22 carotenoids, 4 lipids, a putative Ca2+ ion and 201 water molecules. The structural information on the proteins and cofactors and their interactions provides a basis for understanding how the high efficiency of Photosystem I in light capturing and electron transfer is achieved.
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crystal structure of Photosystem ii from synechococcus elongatus at 3 8 a resolution
Nature, 2001Co-Authors: Athina Zouni, Jan Kern, Petra Fromme, Wolfram Saenger, Norbert Krauss, H T Witt, Peter OrthAbstract:Oxygenic photosynthesis is the principal energy converter on earth. It is driven by Photosystems I and II, two large protein–cofactor complexes located in the thylakoid membrane and acting in series. In Photosystem II, water is oxidized; this event provides the overall process with the necessary electrons and protons, and the atmosphere with oxygen. To date, structural information on the architecture of the complex has been provided by electron microscopy of intact, active Photosystem II at 15–30 A resolution1, and by electron crystallography on two-dimensional crystals of D1-D2-CP47 Photosystem II fragments without water oxidizing activity at 8 A resolution2. Here we describe the X-ray structure of Photosystem II on the basis of crystals fully active in water oxidation3. The structure shows how protein subunits and cofactors are spatially organized. The larger subunits are assigned and the locations and orientations of the cofactors are defined. We also provide new information on the position, size and shape of the manganese cluster, which catalyzes water oxidation.
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Structure of Photosystem I
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2001Co-Authors: Petra Fromme, Patrick Jordan, Norbert KraussAbstract:AbstractIn plants and cyanobacteria, the primary step in oxygenic photosynthesis, the light induced charge separation, is driven by two large membrane intrinsic protein complexes, the Photosystems I and II. Photosystem I catalyses the light driven electron transfer from plastocyanin/cytochrome c6 on the lumenal side of the membrane to ferredoxin/flavodoxin at the stromal side by a chain of electron carriers. Photosystem I of Synechococcus elongatus consists of 12 protein subunits, 96 chlorophyll a molecules, 22 carotenoids, three [4Fe4S] clusters and two phylloquinones. Furthermore, it has been discovered that four lipids are intrinsic components of Photosystem I. Photosystem I exists as a trimer in the native membrane with a molecular mass of 1068 kDa for the whole complex. The X-ray structure of Photosystem I at a resolution of 2.5 Å shows the location of the individual subunits and cofactors and provides new information on the protein–cofactor interactions. [P. Jordan, P. Fromme, H.T. Witt, O. Klukas, W. Saenger, N. Krauß, Nature 411 (2001) 909-917]. In this review, biochemical data and results of biophysical investigations are discussed with respect to the X-ray crystallographic structure in order to give an overview of the structure and function of this large membrane protein
