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Wlodarczyk LM, Snellenburg JJ, Ihalainen JA, van Grondelle R, van Stokkum IHM, Dekker JP. Functional rearrangement of the light-harvesting antenna upon state transitions in a green alga. Biophys J 2015; 108:261-71. [PMID: 25606675 PMCID: PMC4302191 DOI: 10.1016/j.bpj.2014.11.3470] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 11/19/2014] [Accepted: 11/26/2014] [Indexed: 12/12/2022] Open
Abstract
State transitions in the green alga Chlamydomonas reinhardtii serve to balance excitation energy transfer to photosystem I (PSI) and to photosystem II (PSII) and possibly play a role as a photoprotective mechanism. Thus, light-harvesting complex II (LHCII) can switch between the photosystems consequently transferring more excitation energy to PSII (state 1) or to PSI (state 2) or can end up in LHCII-only domains. In this study, low-temperature (77 K) steady-state and time-resolved fluorescence measured on intact cells of Chlamydomonas reinhardtii shows that independently of the state excitation energy transfer from LHCII to PSI or to PSII occurs on two main timescales of <15 ps and ∼ 100 ps. Moreover, in state 1 almost all LHCIIs are functionally connected to PSII, whereas the transition from state 1 to a state 2 chemically locked by 0.1 M sodium fluoride leads to an almost complete functional release of LHCIIs from PSII. About 2/3 of the released LHCIIs transfer energy to PSI and ∼ 1/3 of the released LHCIIs form a component designated X-685 peaking at 685 nm that decays with time constants of 0.28 and 5.8 ns and does not transfer energy to PSI or to PSII. A less complete state 2 was obtained in cells incubated under anaerobic conditions without chemical locking. In this state about half of all LHCIIs remained functionally connected to PSII, whereas the remaining half became functionally connected to PSI or formed X-685 in similar amounts as with chemical locking. We demonstrate that X-685 originates from LHCII domains not connected to a photosystem and that its presence introduces a change in the interpretation of 77 K steady-state fluorescence emission measured upon state transitions in Chalamydomonas reinhardtii.
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Affiliation(s)
- Lucyna M Wlodarczyk
- Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, Amsterdam, The Netherlands.
| | - Joris J Snellenburg
- Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, Amsterdam, The Netherlands
| | - Janne A Ihalainen
- Nanoscience Center, Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland
| | - Rienk van Grondelle
- Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, Amsterdam, The Netherlands
| | - Ivo H M van Stokkum
- Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, Amsterdam, The Netherlands
| | - Jan P Dekker
- Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, Amsterdam, The Netherlands
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Kim E, Ahn TK, Kumazaki S. Changes in Antenna Sizes of Photosystems during State Transitions in Granal and Stroma-Exposed Thylakoid Membrane of Intact Chloroplasts in Arabidopsis Mesophyll Protoplasts. ACTA ACUST UNITED AC 2015; 56:759-68. [DOI: 10.1093/pcp/pcv004] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 01/13/2015] [Indexed: 11/13/2022]
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53
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Büchel C. Evolution and function of light harvesting proteins. JOURNAL OF PLANT PHYSIOLOGY 2015; 172:62-75. [PMID: 25240794 DOI: 10.1016/j.jplph.2014.04.018] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Revised: 04/11/2014] [Accepted: 04/14/2014] [Indexed: 05/10/2023]
Abstract
Photosynthetic eukaryotes exhibit very different light-harvesting proteins, but all contain membrane-intrinsic light-harvesting complexes (Lhcs), either as additional or sole antennae. Lhcs non-covalently bind chlorophyll a and in most cases another Chl, as well as very different carotenoids, depending on the taxon. The proteins fall into two major groups: The well-defined Lhca/b group of proteins binds typically Chl b and lutein, and the group is present in the 'green lineage'. The other group consists of Lhcr/Lhcf, Lhcz and Lhcx/LhcSR proteins. The former are found in the so-called Chromalveolates, where they mostly bind Chl c and carotenoids very efficient in excitation energy transfer, and in their red algae ancestors. Lhcx/LhcSR are present in most Chromalveolates and in some members of the green lineage as well. Lhcs function in light harvesting, but also in photoprotection, and they influence the organisation of the thylakoid membrane. The different functions of the Lhc subfamilies are discussed in the light of their evolution.
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Affiliation(s)
- Claudia Büchel
- Goethe University Frankfurt, Institute of Molecular Biosciences, Max von Laue Str. 9, 60438 Frankfurt, Germany.
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Berger H, Blifernez-Klassen O, Ballottari M, Bassi R, Wobbe L, Kruse O. Integration of carbon assimilation modes with photosynthetic light capture in the green alga Chlamydomonas reinhardtii. MOLECULAR PLANT 2014; 7:1545-1559. [PMID: 25038233 DOI: 10.1093/mp/ssu083] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The unicellular green alga Chlamydomonas reinhardtii is capable of using organic and inorganic carbon sources simultaneously, which requires the adjustment of photosynthetic activity to the prevailing mode of carbon assimilation. We obtained novel insights into the regulation of light-harvesting at photosystem II (PSII) following altered carbon source availability. In C. reinhardtii, synthesis of PSII-associated light-harvesting proteins (LHCBMs) is controlled by the cytosolic RNA-binding protein NAB1, which represses translation of particular LHCBM isoform transcripts. This mechanism is fine-tuned via regulation of the nuclear NAB1 promoter, which is activated when linear photosynthetic electron flow is restricted by CO(2)-limitation in a photoheterotrophic context. In the wild-type, accumulation of NAB1 reduces the functional PSII antenna size, thus preventing a harmful overexcited state of PSII, as observed in a NAB1-less mutant. We further demonstrate that translation control as a newly identified long-term response to prolonged CO(2)-limitation replaces LHCII state transitions as a fast response to PSII over-excitation. Intriguingly, activation of the long-term response is perturbed in state transition mutant stt7, suggesting a regulatory link between the long- and short-term response. We depict a regulatory circuit operating on distinct timescales and in different cellular compartments to fine-tune light-harvesting in photoheterotrophic eukaryotes.
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Affiliation(s)
- Hanna Berger
- a Bielefeld University, Faculty of Biology, Center for Biotechnology (CeBiTec), Universitätsstrasse 27, 33615, Bielefeld, Germany
| | - Olga Blifernez-Klassen
- a Bielefeld University, Faculty of Biology, Center for Biotechnology (CeBiTec), Universitätsstrasse 27, 33615, Bielefeld, Germany
| | - Matteo Ballottari
- b Universita degli Studi di Verona, Department of Biotechnology, strada Le Grazie 15, 37134, Verona, Italy
| | - Roberto Bassi
- b Universita degli Studi di Verona, Department of Biotechnology, strada Le Grazie 15, 37134, Verona, Italy
| | - Lutz Wobbe
- a Bielefeld University, Faculty of Biology, Center for Biotechnology (CeBiTec), Universitätsstrasse 27, 33615, Bielefeld, Germany
| | - Olaf Kruse
- a Bielefeld University, Faculty of Biology, Center for Biotechnology (CeBiTec), Universitätsstrasse 27, 33615, Bielefeld, Germany
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55
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Natural strategies for photosynthetic light harvesting. Nat Chem Biol 2014; 10:492-501. [PMID: 24937067 DOI: 10.1038/nchembio.1555] [Citation(s) in RCA: 566] [Impact Index Per Article: 56.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 05/15/2014] [Indexed: 12/13/2022]
Abstract
Photosynthetic organisms are crucial for life on Earth as they provide food and oxygen and are at the basis of most energy resources. They have a large variety of light-harvesting strategies that allow them to live nearly everywhere where sunlight can penetrate. They have adapted their pigmentation to the spectral composition of light in their habitat, they acclimate to slowly varying light intensities and they rapidly respond to fast changes in light quality and quantity. This is particularly important for oxygen-producing organisms because an overdose of light in combination with oxygen can be lethal. Rapid progress is being made in understanding how different organisms maximize light harvesting and minimize deleterious effects. Here we summarize the latest findings and explain the main design principles used in nature. The available knowledge can be used for optimizing light harvesting in both natural and artificial photosynthesis to improve light-driven production processes.
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56
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Saito A, Shimizu M, Nakamura H, Maeno S, Katase R, Miwa E, Higuchi K, Sonoike K. Fe deficiency induces phosphorylation and translocation of Lhcb1 in barley thylakoid membranes. FEBS Lett 2014; 588:2042-8. [DOI: 10.1016/j.febslet.2014.04.031] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2014] [Revised: 04/02/2014] [Accepted: 04/22/2014] [Indexed: 11/29/2022]
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Chloroplast remodeling during state transitions in Chlamydomonas reinhardtii as revealed by noninvasive techniques in vivo. Proc Natl Acad Sci U S A 2014; 111:5042-7. [PMID: 24639515 DOI: 10.1073/pnas.1322494111] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Plants respond to changes in light quality by regulating the absorption capacity of their photosystems. These short-term adaptations use redox-controlled, reversible phosphorylation of the light-harvesting complexes (LHCIIs) to regulate the relative absorption cross-section of the two photosystems (PSs), commonly referred to as state transitions. It is acknowledged that state transitions induce substantial reorganizations of the PSs. However, their consequences on the chloroplast structure are more controversial. Here, we investigate how state transitions affect the chloroplast structure and function using complementary approaches for the living cells of Chlamydomonas reinhardtii. Using small-angle neutron scattering, we found a strong periodicity of the thylakoids in state 1, with characteristic repeat distances of ∼ 200 Å, which was almost completely lost in state 2. As revealed by circular dichroism, changes in the thylakoid periodicity were paralleled by modifications in the long-range order arrangement of the photosynthetic complexes, which was reduced by ∼ 20% in state 2 compared with state 1, but was not abolished. Furthermore, absorption spectroscopy reveals that the enhancement of PSI antenna size during state 1 to state 2 transition (∼ 20%) is not commensurate to the decrease in PSII antenna size (∼ 70%), leading to the possibility that a large part of the phosphorylated LHCIIs do not bind to PSI, but instead form energetically quenched complexes, which were shown to be either associated with PSII supercomplexes or in a free form. Altogether these noninvasive in vivo approaches allow us to present a more likely scenario for state transitions that explains their molecular mechanism and physiological consequences.
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Shibata Y, Katoh W, Chiba T, Namie K, Ohnishi N, Minagawa J, Nakanishi H, Noguchi T, Fukumura H. Development of a novel cryogenic microscope with numerical aperture of 0.9 and its application to photosynthesis research. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:880-7. [PMID: 24650629 DOI: 10.1016/j.bbabio.2014.03.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 03/05/2014] [Accepted: 03/10/2014] [Indexed: 01/15/2023]
Abstract
A novel cryogenic optical-microscope system was developed in which the objective lens is set inside of the cryostat adiabatic vacuum space. Being isolated from the sample when it was cooled, the objective lens was maintained at room temperature during the cryogenic measurement. Therefore, the authors were able to use a color-aberration corrected objective lens with a numerical aperture of 0.9. The lens is equipped with an air vent for compatibility to the vacuum. The theoretically expected spatial resolutions of 0.39μm along the lateral direction and 1.3μm along the axial direction were achieved by the developed system. The system was applied to the observations of non-uniform distributions of the photosystems in the cells of a green alga, Chlamydomonas reinhardtii, at 94K. Gaussian decomposition analysis of the fluorescence spectra at all the pixels clearly demonstrated a non-uniform distribution of the two photosystems, as reflected in the variable ratios of the fluorescence intensities assigned to photosystem II and to those assigned to photosystem I. The system was also applied to the fluorescence spectroscopy of single isolated photosystem I complexes at 90K. The fluorescence, assigned to be emitted from a single photosystem I trimer, showed an intermittent fluctuation called blinking, which is typical for a fluorescence signal from a single molecule. The vibronic fluorescence bands at around 790nm were observed for single photosystem I trimers, suggesting that the color aberration is not serious up to the 800nm spectral region.
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Affiliation(s)
- Yutaka Shibata
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki aza Aoba, Aoba-ku, Sendai 980-8578, Japan.
| | - Wataru Katoh
- Division of Material Science (Physics), Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
| | - Tomofumi Chiba
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki aza Aoba, Aoba-ku, Sendai 980-8578, Japan
| | - Keisuke Namie
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki aza Aoba, Aoba-ku, Sendai 980-8578, Japan
| | - Norikazu Ohnishi
- Division of Environmental Photobiology, National Institute for Basic Biology, Okazaki 444-8585, Japan
| | - Jun Minagawa
- Division of Environmental Photobiology, National Institute for Basic Biology, Okazaki 444-8585, Japan
| | - Hanayo Nakanishi
- Division of Material Science (Physics), Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
| | - Takumi Noguchi
- Division of Material Science (Physics), Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
| | - Hiroshi Fukumura
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki aza Aoba, Aoba-ku, Sendai 980-8578, Japan
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59
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State transitions in Chlamydomonas reinhardtii strongly modulate the functional size of photosystem II but not of photosystem I. Proc Natl Acad Sci U S A 2014; 111:3460-5. [PMID: 24550508 DOI: 10.1073/pnas.1319164111] [Citation(s) in RCA: 115] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
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.
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60
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Jajoo A, Mekala NR, Tongra T, Tiwari A, Grieco M, Tikkanen M, Aro EM. Low pH-induced regulation of excitation energy between the two photosystems. FEBS Lett 2014; 588:970-4. [PMID: 24530686 DOI: 10.1016/j.febslet.2014.01.056] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 01/28/2014] [Accepted: 01/28/2014] [Indexed: 11/18/2022]
Abstract
Earlier studies have proposed that low pH causes state transitions in spinach thylakoid membranes. Several Arabidopsis mutants (stn7 incapable in phosphorylation of LHC II, stn8 incapable in phosphorylation of PSII core proteins, stn7 stn8 double mutant and npq4 lacking PsbS and hence qE) were used to investigate the mechanisms involved in low pH induced changes in the thylakoid membrane. We propose that protonation of PsbS at low pH is involved in enhancing energy spillover to PS I.
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Affiliation(s)
- Anjana Jajoo
- School of Life Science, Devi Ahilya University, Indore, M.P., India.
| | - Nageswara Rao Mekala
- Department of Biochemistry, Molecular Plant Biology, University of Turku, FI-20014 Turku, Finland
| | - Teena Tongra
- School of Life Science, Devi Ahilya University, Indore, M.P., India
| | - Arjun Tiwari
- Department of Biochemistry, Molecular Plant Biology, University of Turku, FI-20014 Turku, Finland
| | - Michele Grieco
- Department of Biochemistry, Molecular Plant Biology, University of Turku, FI-20014 Turku, Finland
| | - Mikko Tikkanen
- Department of Biochemistry, Molecular Plant Biology, University of Turku, FI-20014 Turku, Finland
| | - Eva-Mari Aro
- Department of Biochemistry, Molecular Plant Biology, University of Turku, FI-20014 Turku, Finland.
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61
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Iwai M, Yokono M, Nakano A. Visualizing structural dynamics of thylakoid membranes. Sci Rep 2014; 4:3768. [PMID: 24442007 PMCID: PMC3895878 DOI: 10.1038/srep03768] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Accepted: 12/27/2013] [Indexed: 11/10/2022] Open
Abstract
To optimize photosynthesis, light-harvesting antenna proteins regulate light energy dissipation and redistribution in chloroplast thylakoid membranes, which involve dynamic protein reorganization of photosystems I and II. However, direct evidence for such protein reorganization has not been visualized in live cells. Here we demonstrate structural dynamics of thylakoid membranes by live cell imaging in combination with deconvolution. We observed chlorophyll fluorescence in the antibiotics-induced macrochloroplast in the moss Physcomitrella patens. The three-dimensional reconstruction uncovered the fine thylakoid membrane structure in live cells. The time-lapse imaging shows that the entire thylakoid membrane network is structurally stable, but the individual thylakoid membrane structure is flexible in vivo. Our observation indicates that grana serve as a framework to maintain structural integrity of the entire thylakoid membrane network. Both the structural stability and flexibility of thylakoid membranes would be essential for dynamic protein reorganization under fluctuating light environments.
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Affiliation(s)
- Masakazu Iwai
- 1] Live Cell Molecular Imaging Research Team, Extreme Photonics Research Group, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan [2] PRESTO, Japan Science and Technology Agency (JST), Honcho, Kawaguchi, Saitama 332-0012 Japan
| | - Makio Yokono
- Institute of Low Temperature Science, Hokkaido University, Sapporo, Hokkaido 060-0819 Japan
| | - Akihiko Nakano
- 1] Live Cell Molecular Imaging Research Team, Extreme Photonics Research Group, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan [2] Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
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62
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Finazzi G, Minagawa J. High Light Acclimation in Green Microalgae. ADVANCES IN PHOTOSYNTHESIS AND RESPIRATION 2014. [DOI: 10.1007/978-94-017-9032-1_21] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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63
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Abstract
Photosynthetic organisms are continuously subjected to changes in light quantity and quality, and must adjust their photosynthetic machinery so that it maintains optimal performance under limiting light and minimizes photodamage under excess light. To achieve this goal, these organisms use two main strategies in which light-harvesting complex II (LHCII), the light-harvesting system of photosystem II (PSII), plays a key role both for the collection of light energy and for photoprotection. The first is energy-dependent nonphotochemical quenching, whereby the high-light-induced proton gradient across the thylakoid membrane triggers a process in which excess excitation energy is harmlessly dissipated as heat. The second involves a redistribution of the mobile LHCII between the two photosystems in response to changes in the redox poise of the electron transport chain sensed through a signaling chain. These two processes strongly diminish the production of damaging reactive oxygen species, but photodamage of PSII is unavoidable, and it is repaired efficiently.
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Affiliation(s)
- Jean-David Rochaix
- Departments of Molecular Biology and Plant Biology, University of Geneva, 1211 Geneva, Switzerland;
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64
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Iwai M, Pack CG, Takenaka Y, Sako Y, Nakano A. Photosystem II antenna phosphorylation-dependent protein diffusion determined by fluorescence correlation spectroscopy. Sci Rep 2013; 3:2833. [PMID: 24088948 PMCID: PMC3789154 DOI: 10.1038/srep02833] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Accepted: 09/09/2013] [Indexed: 11/20/2022] Open
Abstract
Flexibility of chloroplast thylakoid membrane proteins is essential for plant fitness and survival under fluctuating light environments. Phosphorylation of light-harvesting antenna complex II (LHCII) is known to induce dynamic protein reorganization that fine-tunes the rate of energy conversion in each photosystem. However, molecular details of how LHCII phosphorylation causes light energy redistribution throughout thylakoid membranes still remain unclear. By using fluorescence correlation spectroscopy, we here determined the LHCII phosphorylation-dependent protein diffusion in thylakoid membranes isolated from the green alga Chlamydomonas reinhardtii. As compared to the LHCII dephosphorylation-induced condition, the diffusion coefficient of LHCII increased nearly twofold under the LHCII phosphorylation-induced condition. We also verified the results by using the LHCII phosphorylation-deficient mutant. Our observation suggests that LHCII phosphorylation-dependent protein reorganization occurs along with the changes in the rate of protein diffusion, which would have an important role in mediating light energy redistribution throughout thylakoid membranes.
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Affiliation(s)
- Masakazu Iwai
- 1] Live Cell Molecular Imaging Research Team, Extreme Photonics Research Group, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan [2] PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
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65
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Kaňa R. Mobility of photosynthetic proteins. PHOTOSYNTHESIS RESEARCH 2013; 116:465-79. [PMID: 23955784 DOI: 10.1007/s11120-013-9898-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Accepted: 07/18/2013] [Indexed: 05/03/2023]
Abstract
The mobility of photosynthetic proteins represents an important factor that affects light-energy conversion in photosynthesis. The specific feature of photosynthetic proteins mobility can be currently measured in vivo using advanced microscopic methods, such as fluorescence recovery after photobleaching which allows the direct observation of photosynthetic proteins mobility on a single cell level. The heterogeneous organization of thylakoid membrane proteins results in heterogeneity in protein mobility. The thylakoid membrane contains both, protein-crowded compartments with immobile proteins and fluid areas (less crowded by proteins), allowing restricted diffusion of proteins. This heterogeneity represents an optimal balance as protein crowding is necessary for efficient light-energy conversion, and protein mobility plays an important role in the regulation of photosynthesis. The mobility is required for an optimal light-harvesting process (e.g., during state transitions), and also for transport of proteins during their synthesis or repair. Protein crowding is then a key limiting factor of thylakoid membrane protein mobility; the less thylakoid membranes are crowded by proteins, the higher protein mobility is observed. Mobility of photosynthetic proteins outside the thylakoid membrane (lumen and stroma/cytosol) is less understood. Cyanobacterial phycobilisomes attached to the stromal side of the thylakoid can move relatively fast. Therefore, it seems that stroma with their active enzymes of the Calvin-Benson cycle, are a more fluid compartment in comparison to the rather rigid thylakoid lumen. In conclusion, photosynthetic protein diffusion is generally slower in comparison to similarly sized proteins from other eukaryotic membranes or organelles. Mobility of photosynthetic proteins resembles restricted protein diffusion in bacteria, and has been rationalized by high protein crowding similar to that of thylakoids.
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Affiliation(s)
- Radek Kaňa
- Department of photothrophic microorganisms - Algatech, Institute of Microbiology, Academy of Sciences of the Czech Republic, Opatovický mlýn, 379 81, Třeboň, Czech Republic,
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66
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Schneider A, Geissler P. Coexistence of fluid and crystalline phases of proteins in photosynthetic membranes. Biophys J 2013; 105:1161-70. [PMID: 24010659 PMCID: PMC3762348 DOI: 10.1016/j.bpj.2013.06.052] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 05/26/2013] [Accepted: 06/03/2013] [Indexed: 11/22/2022] Open
Abstract
Photosystem II (PSII) and its associated light-harvesting complex II (LHCII) are highly concentrated in the stacked grana regions of photosynthetic thylakoid membranes. PSII-LHCII supercomplexes can be arranged in disordered packings, ordered arrays, or mixtures thereof. The physical driving forces underlying array formation are unknown, complicating attempts to determine a possible functional role for arrays in regulating light harvesting or energy conversion efficiency. Here, we introduce a coarse-grained model of protein interactions in coupled photosynthetic membranes, focusing on just two particle types that feature simple shapes and potential energies motivated by structural studies. Reporting on computer simulations of the model's equilibrium fluctuations, we demonstrate its success in reproducing diverse structural features observed in experiments, including extended PSII-LHCII arrays. Free energy calculations reveal that the appearance of arrays marks a phase transition from the disordered fluid state to a system-spanning crystal. The predicted region of fluid-crystal coexistence is broad, encompassing much of the physiologically relevant parameter regime; we propose experiments that could test this prediction. Our results suggest that grana membranes lie at or near phase coexistence, conferring significant structural and functional flexibility to this densely packed membrane protein system.
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Affiliation(s)
- Anna R. Schneider
- Biophysics Graduate Group, University of California, Berkeley, California
| | - Phillip L. Geissler
- Department of Chemistry, University of California, Berkeley, California and Chemical Sciences and Physical Biosciences Divisions, Lawrence Berkeley National Lab, Berkeley, California
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67
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Janik E, Bednarska J, Zubik M, Puzio M, Luchowski R, Grudzinski W, Mazur R, Garstka M, Maksymiec W, Kulik A, Dietler G, Gruszecki WI. Molecular architecture of plant thylakoids under physiological and light stress conditions: a study of lipid-light-harvesting complex II model membranes. THE PLANT CELL 2013; 25:2155-70. [PMID: 23898030 PMCID: PMC3723618 DOI: 10.1105/tpc.113.113076] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Revised: 05/31/2013] [Accepted: 06/12/2013] [Indexed: 05/19/2023]
Abstract
In this study, we analyzed multibilayer lipid-protein membranes composed of the photosynthetic light-harvesting complex II (LHCII; isolated from spinach [Spinacia oleracea]) and the plant lipids monogalcatosyldiacylglycerol and digalactosyldiacylglycerol. Two types of pigment-protein complexes were analyzed: those isolated from dark-adapted leaves (LHCII) and those from leaves preilluminated with high-intensity light (LHCII-HL). The LHCII-HL complexes were found to be partially phosphorylated and contained zeaxanthin. The results of the x-ray diffraction, infrared imaging microscopy, confocal laser scanning microscopy, and transmission electron microscopy revealed that lipid-LHCII membranes assemble into planar multibilayers, in contrast with the lipid-LHCII-HL membranes, which form less ordered structures. In both systems, the protein formed supramolecular structures. In the case of LHCII-HL, these structures spanned the multibilayer membranes and were perpendicular to the membrane plane, whereas in LHCII, the structures were lamellar and within the plane of the membranes. Lamellar aggregates of LHCII-HL have been shown, by fluorescence lifetime imaging microscopy, to be particularly active in excitation energy quenching. Both types of structures were stabilized by intermolecular hydrogen bonds. We conclude that the formation of trans-layer, rivet-like structures of LHCII is an important determinant underlying the spontaneous formation and stabilization of the thylakoid grana structures, since the lamellar aggregates are well suited to dissipate excess energy upon overexcitation.
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Affiliation(s)
- Ewa Janik
- Department of Biophysics, Institute of Physics, Maria Curie-Sklodowska University, 20-031 Lublin, Poland
| | - Joanna Bednarska
- Department of Biophysics, Institute of Physics, Maria Curie-Sklodowska University, 20-031 Lublin, Poland
| | - Monika Zubik
- Department of Biophysics, Institute of Physics, Maria Curie-Sklodowska University, 20-031 Lublin, Poland
| | - Michal Puzio
- Department of Biophysics, Institute of Physics, Maria Curie-Sklodowska University, 20-031 Lublin, Poland
| | - Rafal Luchowski
- Department of Biophysics, Institute of Physics, Maria Curie-Sklodowska University, 20-031 Lublin, Poland
| | - Wojciech Grudzinski
- Department of Biophysics, Institute of Physics, Maria Curie-Sklodowska University, 20-031 Lublin, Poland
| | - Radoslaw Mazur
- Department of Metabolic Regulation, Institute of Biochemistry, Faculty of Biology, University of Warsaw, 02-096 Warsaw, Poland
| | - Maciej Garstka
- Department of Metabolic Regulation, Institute of Biochemistry, Faculty of Biology, University of Warsaw, 02-096 Warsaw, Poland
| | - Waldemar Maksymiec
- Department of Plant Physiology, Institute of Biology and Biochemistry, Maria Curie-Sklodowska University, 20-033 Lublin, Poland
| | - Andrzej Kulik
- Laboratoire de Physique de la Matière Vivante, Institut de Physique des Systèmes Biologiques, Ecole Polytechnique Fédérale de Lausanne, CH 1015 Lausanne, Switzerland
| | - Giovanni Dietler
- Laboratoire de Physique de la Matière Vivante, Institut de Physique des Systèmes Biologiques, Ecole Polytechnique Fédérale de Lausanne, CH 1015 Lausanne, Switzerland
| | - Wieslaw I. Gruszecki
- Department of Biophysics, Institute of Physics, Maria Curie-Sklodowska University, 20-031 Lublin, Poland
- Address correspondence to
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68
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Janik E, Bednarska J, Zubik M, Puzio M, Luchowski R, Grudzinski W, Mazur R, Garstka M, Maksymiec W, Kulik A, Dietler G, Gruszecki WI. Molecular architecture of plant thylakoids under physiological and light stress conditions: a study of lipid-light-harvesting complex II model membranes. THE PLANT CELL 2013; 25:2155-2170. [PMID: 23898030 DOI: 10.2307/23482454] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
In this study, we analyzed multibilayer lipid-protein membranes composed of the photosynthetic light-harvesting complex II (LHCII; isolated from spinach [Spinacia oleracea]) and the plant lipids monogalcatosyldiacylglycerol and digalactosyldiacylglycerol. Two types of pigment-protein complexes were analyzed: those isolated from dark-adapted leaves (LHCII) and those from leaves preilluminated with high-intensity light (LHCII-HL). The LHCII-HL complexes were found to be partially phosphorylated and contained zeaxanthin. The results of the x-ray diffraction, infrared imaging microscopy, confocal laser scanning microscopy, and transmission electron microscopy revealed that lipid-LHCII membranes assemble into planar multibilayers, in contrast with the lipid-LHCII-HL membranes, which form less ordered structures. In both systems, the protein formed supramolecular structures. In the case of LHCII-HL, these structures spanned the multibilayer membranes and were perpendicular to the membrane plane, whereas in LHCII, the structures were lamellar and within the plane of the membranes. Lamellar aggregates of LHCII-HL have been shown, by fluorescence lifetime imaging microscopy, to be particularly active in excitation energy quenching. Both types of structures were stabilized by intermolecular hydrogen bonds. We conclude that the formation of trans-layer, rivet-like structures of LHCII is an important determinant underlying the spontaneous formation and stabilization of the thylakoid grana structures, since the lamellar aggregates are well suited to dissipate excess energy upon overexcitation.
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Affiliation(s)
- Ewa Janik
- Department of Biophysics, Institute of Physics, Maria Curie-Sklodowska University, 20-031 Lublin, Poland
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69
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Kowalczyk N, Rappaport F, Boyen C, Wollman FA, Collén J, Joliot P. Photosynthesis in Chondrus crispus: the contribution of energy spill-over in the regulation of excitonic flux. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1827:834-42. [PMID: 23624348 DOI: 10.1016/j.bbabio.2013.04.004] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 03/13/2013] [Accepted: 04/09/2013] [Indexed: 11/26/2022]
Abstract
Chondrus crispus is a species of red algae that grows on rocks from the middle intertidal into the subtidal zones of the North Atlantic coasts. As such, it has to cope with strongly variable abiotic conditions. Here we studied the response of the photosynthetic apparatus of this red alga to illumination. We found that, as previously described in the case of the unicellular alga Rhodella violacea (E. Delphin et al., Plant Physiol. 118 (1998) 103-113), a single multi-turnover saturating pulse of light is sufficient to induce a strong quenching of fluorescence. To elucidate the mechanisms underlying this fluorescence quenching, we combined room temperature and 77K fluorescence measurements with absorption spectroscopy to monitor the redox state of the different electron carriers in the chain. In addition, we studied the dependence of these various observables upon the excitation wavelength. This led us to identify energy spill-over from Photosystem II to Photosystem I rather than a qE-type non-photochemical quenching as the major source of fluorescence quenching that develops upon a series of 200ms pulses of saturating light results, in line with the conclusion of Ley and Butler (Biochim. Biophys. Acta 592 (1980) 349-363) from their studies of the unicellular red alga Porphyridium cruentum. In addition, we show that the onset of this spill-over is triggered by the reduction of the plastoquinone pool.
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70
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Takahashi H, Clowez S, Wollman FA, Vallon O, Rappaport F. Cyclic electron flow is redox-controlled but independent of state transition. Nat Commun 2013; 4:1954. [PMID: 23760547 PMCID: PMC3709502 DOI: 10.1038/ncomms2954] [Citation(s) in RCA: 137] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Accepted: 04/29/2013] [Indexed: 11/23/2022] Open
Abstract
Photosynthesis is the biological process that feeds the biosphere with reduced carbon. The assimilation of CO2 requires the fine tuning of two co-existing functional modes: linear electron flow, which provides NADPH and ATP, and cyclic electron flow, which only sustains ATP synthesis. Although the importance of this fine tuning is appreciated, its mechanism remains equivocal. Here we show that cyclic electron flow as well as formation of supercomplexes, thought to contribute to the enhancement of cyclic electron flow, are promoted in reducing conditions with no correlation with the reorganization of the thylakoid membranes associated with the migration of antenna proteins towards Photosystems I or II, a process known as state transition. We show that cyclic electron flow is tuned by the redox power and this provides a mechanistic model applying to the entire green lineage including the vast majority of the cases in which state transition only involves a moderate fraction of the antenna.
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Affiliation(s)
- Hiroko Takahashi
- Institut de Biologie Physico-Chimique, UMR 7141 CNRS-UPMC, 13 rue P et M Curie, 75005 Paris, France
- These authors contributed equally to this work
| | - Sophie Clowez
- Institut de Biologie Physico-Chimique, UMR 7141 CNRS-UPMC, 13 rue P et M Curie, 75005 Paris, France
- These authors contributed equally to this work
| | - Francis-André Wollman
- Institut de Biologie Physico-Chimique, UMR 7141 CNRS-UPMC, 13 rue P et M Curie, 75005 Paris, France
| | - Olivier Vallon
- Institut de Biologie Physico-Chimique, UMR 7141 CNRS-UPMC, 13 rue P et M Curie, 75005 Paris, France
| | - Fabrice Rappaport
- Institut de Biologie Physico-Chimique, UMR 7141 CNRS-UPMC, 13 rue P et M Curie, 75005 Paris, France
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71
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Architectural switch in plant photosynthetic membranes induced by light stress. Proc Natl Acad Sci U S A 2012; 109:20130-5. [PMID: 23169624 DOI: 10.1073/pnas.1214265109] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Unavoidable side reactions of photosynthetic energy conversion can damage the water-splitting photosystem II (PSII) holocomplex embedded in the thylakoid membrane system inside chloroplasts. Plant survival is crucially dependent on an efficient molecular repair of damaged PSII realized by a multistep repair cycle. The PSII repair cycle requires a brisk lateral protein traffic between stacked grana thylakoids and unstacked stroma lamellae that is challenged by the tight stacking and low protein mobility in grana. We demonstrated that high light stress induced two main structural changes that work synergistically to improve the accessibility between damaged PSII in grana and its repair machinery in stroma lamellae: lateral shrinkage of grana diameter and increased protein mobility in grana thylakoids. It follows that high light stress triggers an architectural switch of the thylakoid network that is advantageous for swift protein repair. Studies of the thylakoid kinase mutant stn8 and the double mutant stn7/8 demonstrate the central role of protein phosphorylation for the structural alterations. These findings are based on the elaboration of mathematical tools for analyzing confocal laser-scanning microscopic images to study changes in the sophisticated thylakoid architecture in intact protoplasts.
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72
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Zeng Y, Wu Y, Li D, Zheng W, Wang WX, Qu JY. Two-photon excitation chlorophyll fluorescence lifetime imaging: a rapid and noninvasive method for in vivo assessment of cadmium toxicity in a marine diatom Thalassiosira weissflogii. PLANTA 2012; 236:1653-1663. [PMID: 22806228 DOI: 10.1007/s00425-012-1703-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2012] [Accepted: 06/24/2012] [Indexed: 06/01/2023]
Abstract
We demonstrate that a two-photon excitation fluorescence lifetime imaging technology can rapidly and noninvasively assess the cadmium (Cd)-induced toxic effects in a marine diatom Thalassiosira weissflogii. The chlorophyll, an intrinsic fluorophore, was used as a contrast agent for imaging of cellular structures and for assessment of cell toxicity. The assessment is based on an imaging-guided statistical analysis of chlorophyll fluorescence decay. This novel label-free imaging method is physically based and free of tedious preparation and preprocessing of algal samples. We first studied the chlorophyll fluorescence quenching induced by the infrared two-photon excitation laser and found that the quenching effects on the assessment of Cd toxicity could be well controlled and calibrated. In the toxicity study, chlorophyll fluorescence lifetime images were collected from the diatom samples after exposure to different concentrations of Cd. The alteration of chloroplast structure at higher Cd concentration was clearly identified. The decay of chlorophyll fluorescence extracted from recorded pixels of high signal-to-noise ratio in the fluorescence lifetime image was analyzed. The increase of average chlorophyll fluorescence lifetime following Cd treatment was observed, indicating the Cd inhibition effect on the electron transport chain in photosynthesis system. The findings of this study show that the temporal characteristics of chlorophyll fluorescence can potentially be utilized as a biomarker for indicating Cd toxicity noninvasively in algal cells.
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Affiliation(s)
- Yan Zeng
- Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, People's Republic of China.
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73
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Fluorescence lifetime snapshots reveal two rapidly reversible mechanisms of photoprotection in live cells of Chlamydomonas reinhardtii. Proc Natl Acad Sci U S A 2012; 109:8405-10. [PMID: 22586081 DOI: 10.1073/pnas.1205303109] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Photosynthetic organisms avoid photodamage to photosystem II (PSII) in variable light conditions via a suite of photoprotective mechanisms called nonphotochemical quenching (NPQ), in which excess absorbed light is dissipated harmlessly. To quantify the contributions of different quenching mechanisms to NPQ, we have devised a technique to measure the changes in chlorophyll fluorescence lifetime as photosynthetic organisms adapt to varying light conditions. We applied this technique to measure the fluorescence lifetimes responsible for the predominant, rapidly reversible component of NPQ, qE, in living cells of Chlamydomonas reinhardtii. Application of high light to dark-adapted cells of C. reinhardtii led to an increase in the amplitudes of 65 ps and 305 ps chlorophyll fluorescence lifetime components that was reversed after the high light was turned off. Removal of the pH gradient across the thylakoid membrane linked the changes in the amplitudes of the two components to qE quenching. The rise times of the amplitudes of the two components were significantly different, suggesting that the changes are due to two different qE mechanisms. We tentatively suggest that the changes in the 65 ps component are due to charge-transfer quenching in the minor light-harvesting complexes and that the changes in the 305 ps component are due to aggregated light-harvesting complex II trimers that have detached from PSII. We anticipate that this technique will be useful for resolving the various mechanisms of NPQ and for quantifying the timescales associated with these mechanisms.
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74
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Wu Y, Zeng Y, Qu JY, Wang WX. Mercury effects on Thalassiosira weissflogii: applications of two-photon excitation chlorophyll fluorescence lifetime imaging and flow cytometry. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2012; 110-111:133-140. [PMID: 22293220 DOI: 10.1016/j.aquatox.2012.01.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Revised: 12/20/2011] [Accepted: 01/03/2012] [Indexed: 05/31/2023]
Abstract
The toxic effects of inorganic mercury [Hg(II)] and methylmercury (MeHg) on the photosynthesis and population growth in a marine diatom Thalassiosira weissflogii were investigated using two methods: two-photon excitation fluorescence lifetime imaging (FLIM) and flow cytometry (FCM). For photosynthesis, Hg(II) exposure increased the average chlorophyll fluorescence lifetime, whereas such increment was not found under MeHg stress. This may be caused by the inhibitory effect of Hg(II) instead of MeHg on the electron transport chain. For population growth, modeled specific growth rate data showed that the reduction in population growth by Hg(II) mainly resulted from an increased number of injured cells, while the live cells divided at the normal rates. However, MeHg inhibitory effects on population growth were contributed by the reduced division rates of all cells. Furthermore, the cell images and the FCM data reflected the morphological changes of diatom cells under Hg(II)/MeHg exposure vividly and quantitatively. Our results demonstrated that the toxigenicity mechanisms between Hg(II) and MeHg were different in the algal cells.
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Affiliation(s)
- Yun Wu
- Division of Life Science, Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon, Hong Kong, PR China
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75
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Nevo R, Charuvi D, Tsabari O, Reich Z. Composition, architecture and dynamics of the photosynthetic apparatus in higher plants. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 70:157-76. [PMID: 22449050 DOI: 10.1111/j.1365-313x.2011.04876.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The process of oxygenic photosynthesis enabled and still sustains aerobic life on Earth. The most elaborate form of the apparatus that carries out the primary steps of this vital process is the one present in higher plants. Here, we review the overall composition and supramolecular organization of this apparatus, as well as the complex architecture of the lamellar system within which it is harbored. Along the way, we refer to the genetic, biochemical, spectroscopic and, in particular, microscopic studies that have been employed to elucidate the structure and working of this remarkable molecular energy conversion device. As an example of the highly dynamic nature of the apparatus, we discuss the molecular and structural events that enable it to maintain high photosynthetic yields under fluctuating light conditions. We conclude the review with a summary of the hypotheses made over the years about the driving forces that underlie the partition of the lamellar system of higher plants and certain green algae into appressed and non-appressed membrane domains and the segregation of the photosynthetic protein complexes within these domains.
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Affiliation(s)
- Reinat Nevo
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
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76
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Nagy G, Pieper J, Krumova SB, Kovács L, Trapp M, Garab G, Peters J. Dynamic properties of photosystem II membranes at physiological temperatures characterized by elastic incoherent neutron scattering. Increased flexibility associated with the inactivation of the oxygen evolving complex. PHOTOSYNTHESIS RESEARCH 2012; 111:113-24. [PMID: 22052408 DOI: 10.1007/s11120-011-9701-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Accepted: 10/13/2011] [Indexed: 05/02/2023]
Abstract
Elastic incoherent neutron scattering (EINS), a non-invasive technique which is capable of measuring the mean square displacement of atoms in the sample, has been widely used in biology for exploring the dynamics of proteins and lipid membranes but studies on photosynthetic systems are scarce. In this study we investigated the dynamic characteristics of Photosystem II (PSII) membrane fragments between 280 and 340 K, i.e., in the physiological temperature range and in the range of thermal denaturation of some of the protein complexes. The mean square displacement values revealed the presence of a hydration-sensitive transition in the sample between 310 and 320 K, suggesting that the oxygen evolving complex (OEC) plays an important role in the transition. Indeed, in samples in which the OEC had been removed by TRIS- or heat-treatments (323 and 333 K) no such transition was found. Further support on the main role of OEC in these reorganizations is provided by data obtained from differential scanning calorimetry experiments, showing marked differences between the untreated and TRIS-treated samples. In contrast, circular dichroism spectra exhibited only minor changes in the excitonic interactions below 323 K, showing that the molecular organization of the pigment-protein complexes remains essentially unaffected. Our data, along with earlier incoherent neutron scattering data on PSII membranes at cryogenic temperatures (Pieper et al., Biochemistry 46:11398-11409, 2007), demonstrate that this technique can be applied to characterize the dynamic features of PSII membranes, and can be used to investigate photosynthetic membranes under physiologically relevant experimental conditions.
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Affiliation(s)
- Gergely Nagy
- Institut Laue-Langevin, P.O. Box 156, 38042, Grenoble Cedex 9, France
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77
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Yokono M, Uchida H, Suzawa Y, Akiomoto S, Murakami A. Stabilization and modulation of the phycobilisome by calcium in the calciphilic freshwater red alga Bangia atropurpurea. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:306-11. [PMID: 22093772 DOI: 10.1016/j.bbabio.2011.11.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Revised: 10/17/2011] [Accepted: 11/02/2011] [Indexed: 11/19/2022]
Affiliation(s)
- Makio Yokono
- Molecular Photoscience Research Center, Kobe University, Kobe, Hyogo, Japan.
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78
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Jajoo A, Szabó M, Zsiros O, Garab G. Low pH induced structural reorganization in thylakoid membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:1388-91. [PMID: 22248669 DOI: 10.1016/j.bbabio.2012.01.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 12/22/2011] [Accepted: 01/02/2012] [Indexed: 11/19/2022]
Abstract
By using low temperature fluorescence spectroscopy, it has been shown that exposing chloroplast thylakoid membranes to acidic pH reversibly decreases the fluorescence of photosystem II while the fluorescence of photosystem I increases [P. Singh-Rawal et al. (2010) Evidence that pH can drive state transitions in isolated thylakoid membranes from spinach, Photochem Photobiol Sci, 9 830-837]. In order to shed light on the origin of these changes, we performed circular dichroism (CD) spectroscopy on freshly isolated pea thylakoid membranes. We show that the magnitude of the psi-type CD, which is associated with the presence of chirally ordered macroarrays of the chromophores in intact thylakoid membranes, decreases gradually and reversibly upon gradually lowering the pH of the medium from 7.5 to 4.5 (psi, polymer or salt induced). The same treatment, as shown on thylakoid membranes washed in hypotonic low salt medium possessing no psi-type bands, induces no discernible change in the excitonic CD. These data show that while no change in the pigment-pigment interactions and thus in the molecular organization of the bulk protein complexes can be held responsible for the observed changes in the fluorescence, acidification of the medium significantly alters the macro-organization of the complexes, hence providing an explanation for the pH-induced redistribution of the excitation energy between the two photosystems. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.
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Affiliation(s)
- Anjana Jajoo
- School of Life Science, Devi Ahilya University, Indore, India.
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79
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Reversible membrane reorganizations during photosynthesis in vivo: revealed by small-angle neutron scattering. Biochem J 2011; 436:225-30. [PMID: 21473741 DOI: 10.1042/bj20110180] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In the present study, we determined characteristic repeat distances of the photosynthetic membranes in living cyanobacterial and eukaryotic algal cells, and in intact thylakoid membranes isolated from higher plants with time-resolved small-angle neutron scattering. This non-invasive technique reveals light-induced reversible reorganizations in the seconds-to-minutes time scale, which appear to be associated with functional changes in vivo.
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80
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Azarkh M, Okle O, Singh V, Seemann IT, Hartig JS, Dietrich DR, Drescher M. Long-range distance determination in a DNA model system inside Xenopus laevis oocytes by in-cell spin-label EPR. Chembiochem 2011; 12:1992-5. [PMID: 21726034 DOI: 10.1002/cbic.201100281] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Indexed: 12/13/2022]
Affiliation(s)
- Mykhailo Azarkh
- Department of Chemistry, Konstanz Research School Chemical Biology, Zukunftskolleg, University of Konstanz, 78457 Konstanz, Germany
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81
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Yokono M, Murakami A, Akimoto S. Excitation energy transfer between photosystem II and photosystem I in red algae: Larger amounts of phycobilisome enhance spillover. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:847-53. [DOI: 10.1016/j.bbabio.2011.03.014] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Revised: 03/25/2011] [Accepted: 03/29/2011] [Indexed: 10/18/2022]
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82
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Supramolecular organization of photosystem II in green plants. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:2-12. [PMID: 21723248 DOI: 10.1016/j.bbabio.2011.05.024] [Citation(s) in RCA: 161] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Revised: 05/23/2011] [Accepted: 05/26/2011] [Indexed: 01/24/2023]
Abstract
Green plant photosystem II (PSII) is involved in the light reactions of photosynthesis, which take place in the thylakoid membrane of the chloroplast. PSII is organized into large supercomplexes with variable amounts of membrane-bound peripheral antenna complexes. These supercomplexes are dimeric and contain usually 2-4 copies of trimeric LHCII complexes and have a further tendency to associate into megacomplexes or into crystalline domains, of which several types have been characterized. This review focuses on the overall composition and structure of the PSII supercomplex of green plants and its organization and interactions within the photosynthetic membrane. Further, we present the current knowledge how the thylakoid membrane is three-dimensionally organized within the chloroplast. We also discuss how the supramolecular organization in the thylakoid membrane and the PSII flexibility may play roles in various short-term regulatory mechanisms of green plant photosynthesis. This article is part of a Special Issue entitled: Photosystem II.
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83
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Nellaepalli S, Mekala NR, Zsiros O, Mohanty P, Subramanyam R. Moderate heat stress induces state transitions in Arabidopsis thaliana. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:1177-84. [PMID: 21640068 DOI: 10.1016/j.bbabio.2011.05.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2011] [Revised: 05/17/2011] [Accepted: 05/18/2011] [Indexed: 11/29/2022]
Abstract
The effect of temperature on the photosynthetic machinery is crucial for the fundamental understanding of plant physiology and the bioengineering of heat-tolerant varieties. In our study, Arabidopsis thaliana was exposed to mild (40°C), short-term heat stress in the dark to evaluate the heat-triggered phosphorylation and migration of light harvesting complex (LHC) II in both wild-type (wt) and mutant lacking STN7 kinase. The 77K emission spectra revealed an increase in PSI relative to PSII emission similar to increases observed in light-induced state I to state II transitions in wt but not in stn7 mutant. Immunoblotting results indicated that the major LHCII was phosphorylated at threonine sites under heat stress in wt plants but not in the mutant. These results support the proposition that mild heat stress triggers state transitions in the dark similar to light-induced state transitions, which involve phosphorylation of LHCII by STN7 kinase. Pre-treatment of Arabidopsis leaves with inhibitor DBMIB, altered the extent of LHCII phosphorylation and PSI fluorescence emission suggests that activation of STN7 kinase may be dependent on Cyt b(6)/f under elevated temperatures in dark. Furthermore, fast Chl a transient of temperature-exposed leaves of wt showed a decrease in the F(v)/F(m) ratio due to both an increase in F(o) and a decrease in F(m). In summary, our findings indicate that a mild heat treatment (40°C) induces state transitions in the dark resulting in the migration of phosphorylated LHCII from the grana to the stroma region.
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Affiliation(s)
- Sreedhar Nellaepalli
- Department of Biochemistry, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India
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84
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Wu JH, Guan Z, Xu TZ, Xu QH, Xu GQ. Tetracene-doped anthracene nanowire arrays: preparation and doping effects. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:6374-6380. [PMID: 21480618 DOI: 10.1021/la200569v] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Large-scale tetracene-doped anthracene nanowire arrays were prepared, and the doping effects were studied. The high doping concentration up to 10% (molar ratio) has been achieved, attributed to both the unique long-nanowire geometry and the excellent structural compatibility of anthracene and tetracene. The incorporation of long tetracene molecules into the matrix of short anthracene molecules induced an enlarged interlayer thickness, a decreased nanowire thickness, and an expanded nanowire width. The tetracene molecules were homogeneously embedded into the anthracene matrix at low doping concentrations (<1%). The doping became inhomogeneous at high doping concentrations (≥1%). The energy transfer efficiency between anthracene and tetracene is nearly 100% at doping concentrations ≥1%.
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Affiliation(s)
- Ji Hong Wu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Republic of Singapore 117543
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85
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Lambrev PH, Schmitt FJ, Kussin S, Schoengen M, Várkonyi Z, Eichler HJ, Garab G, Renger G. Functional domain size in aggregates of light-harvesting complex II and thylakoid membranes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:1022-31. [PMID: 21616053 DOI: 10.1016/j.bbabio.2011.05.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Revised: 05/03/2011] [Accepted: 05/06/2011] [Indexed: 11/18/2022]
Abstract
The functional domain size for efficient excited singlet state quenching was studied in artificial aggregates of the main light-harvesting complex II (LHCIIb) from spinach and in native thylakoid membranes by picosecond time-resolved fluorescence spectroscopy and quantum yield measurements. The domain size was estimated from the efficiency of added exogenous singlet excitation quenchers-phenyl-p-benzoquinone (PPQ) and dinitrobenzene (DNB). The mean fluorescence lifetimes τ(av) were quantified for a range of quencher concentrations. Applying the Stern-Volmer formalism, apparent quenching rate constants k(q) were determined from the dependencies on quencher concentration of the ratio τ(0)(av)/τ(av), where τ(0)(av) is the average fluorescence lifetime of the sample without addition of an exogenous quencher. The functional domain size was gathered from the ratio k(q)'/k(q), i.e., the apparent quenching rate constants determined in aggregates (or membranes), k(q)', and in detergent-solubilised LHCII trimers, k(q), respectively. In LHCII macroaggregates, the resulting values for the domain size were 15-30 LHCII trimers. In native thylakoid membranes the domain size was equivalent to 12-24 LHCII trimers, corresponding to 500-1000 chlorophylls. Virtually the same results were obtained when membranes were suspended in buffers promoting either membrane stacking or destacking. These domain sizes are orders of magnitude smaller than the number of physically connected pigment-protein complexes. Therefore our results imply that the physical size of an antenna system beyond the numbers of a functional domain size has little or no effect on improving the light-harvesting efficiency.
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Affiliation(s)
- Petar H Lambrev
- Max-Volmer-Laboratory for Biophysical Chemistry PC 14, Berlin Institute of Technology, Strasse des 17. Juni 135, 10623 Berlin, Germany.
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86
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Johnson MP, Goral TK, Duffy CD, Brain AP, Mullineaux CW, Ruban AV. Photoprotective energy dissipation involves the reorganization of photosystem II light-harvesting complexes in the grana membranes of spinach chloroplasts. THE PLANT CELL 2011; 23:1468-79. [PMID: 21498680 PMCID: PMC3101555 DOI: 10.1105/tpc.110.081646] [Citation(s) in RCA: 253] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Revised: 03/08/2011] [Accepted: 03/28/2011] [Indexed: 05/18/2023]
Abstract
Plants must regulate their use of absorbed light energy on a minute-by-minute basis to maximize the efficiency of photosynthesis and to protect photosystem II (PSII) reaction centers from photooxidative damage. The regulation of light harvesting involves the photoprotective dissipation of excess absorbed light energy in the light-harvesting antenna complexes (LHCs) as heat. Here, we report an investigation into the structural basis of light-harvesting regulation in intact spinach (Spinacia oleracea) chloroplasts using freeze-fracture electron microscopy, combined with laser confocal microscopy employing the fluorescence recovery after photobleaching technique. The results demonstrate that formation of the photoprotective state requires a structural reorganization of the photosynthetic membrane involving dissociation of LHCII from PSII and its aggregation. The structural changes are manifested by a reduced mobility of LHC antenna chlorophyll proteins. It is demonstrated that these changes occur rapidly and reversibly within 5 min of illumination and dark relaxation, are dependent on ΔpH, and are enhanced by the deepoxidation of violaxanthin to zeaxanthin.
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Affiliation(s)
- Matthew P. Johnson
- School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, United Kingdom
| | - Tomasz K. Goral
- School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, United Kingdom
| | - Christopher D.P. Duffy
- School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, United Kingdom
| | - Anthony P.R. Brain
- Centre for Ultrastructural Imaging, Kings College University of London, London SE1 1UL, United Kingdom
| | - Conrad W. Mullineaux
- School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, United Kingdom
| | - Alexander V. Ruban
- School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, United Kingdom
- Address correspondence to
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87
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Photosystem II fluorescence lifetime imaging in avocado leaves: contributions of the lutein-epoxide and violaxanthin cycles to fluorescence quenching. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2011; 104:271-84. [PMID: 21356597 DOI: 10.1016/j.jphotobiol.2011.01.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Revised: 01/03/2011] [Accepted: 01/05/2011] [Indexed: 11/23/2022]
Abstract
Lifetime-resolved imaging measurements of chlorophyll a fluorescence were made on leaves of avocado plants to study whether rapidly reversible ΔpH-dependent (transthylakoid H(+) concentration gradient) thermal energy dissipation (qE) and slowly reversible ΔpH-independent fluorescence quenching (qI) are modulated by lutein-epoxide and violaxanthin cycles operating in parallel. Under normal conditions (without inhibitors), analysis of the chlorophyll a fluorescence lifetime data revealed two major lifetime pools (1.5 and 0.5 ns) for photosystem II during the ΔpH build-up under illumination. Formation of the 0.5-ns pool upon illumination was correlated with dark-retention of antheraxanthin and photo-converted lutein in leaves. Interconversion between the 1.5- and 0.5-ns lifetime pools took place during the slow part of the chlorophyll a fluorescence transient: first from 1.5 ns to 0.5 ns in the P-to-S phase, then back from 0.5 ns to 1.5 ns in the S-to-M phase. When linear electron transport and the resulting ΔpH build-up were inhibited by treatment with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), the major fluorescence intensity was due to a 2.2-ns lifetime pool with a minor faster contribution of approximately 0.7 ns. In the presence of DCMU, neither the intensity nor the lifetimes of fluorescence were affected by antheraxanthin and photo-converted lutein. Thus, we conclude that both antheraxanthin and photo-converted lutein are able to enhance ΔpH-dependent qE processes that are associated with the 0.5-ns lifetime pool. However, unlike zeaxanthin, retention of antheraxanthin and photo-converted lutein may not by itself stabilize quenching or cause qI.
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88
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Krumova SB, Laptenok SP, Borst JW, Ughy B, Gombos Z, Ajlani G, van Amerongen H. Monitoring photosynthesis in individual cells of Synechocystis sp. PCC 6803 on a picosecond timescale. Biophys J 2011; 99:2006-15. [PMID: 20858447 DOI: 10.1016/j.bpj.2010.07.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Revised: 07/09/2010] [Accepted: 07/13/2010] [Indexed: 01/20/2023] Open
Abstract
Picosecond fluorescence kinetics of wild-type (WT) and mutant cells of Synechocystis sp. PCC 6803, were studied at the ensemble level with a streak-camera and at the cell level using fluorescence-lifetime-imaging microscopy (FLIM). The FLIM measurements are in good agreement with the ensemble measurements, but they (can) unveil variations between and within cells. The BE mutant cells, devoid of photosystem II (PSII) and of the light-harvesting phycobilisomes, allowed the study of photosystem I (PSI) in vivo for the first time, and the observed 6-ps equilibration process and 25-ps trapping process are the same as found previously for isolated PSI. No major differences are detected between different cells. The PAL mutant cells, devoid of phycobilisomes, show four lifetimes: ∼20 ps (PSI and PSII), ∼80 ps, ∼440 ps, and 2.8 ns (all due to PSII), but not all cells are identical and variations in the kinetics are traced back to differences in the PSI/PSII ratio. Finally, FLIM measurements on WT cells reveal that in some cells or parts of cells, phycobilisomes are disconnected from PSI/PSII. It is argued that the FLIM setup used can become instrumental in unraveling photosynthetic regulation mechanisms in the future.
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Affiliation(s)
- S B Krumova
- Laboratory of Biophysics, Wageningen University, Wageningen, The Netherlands
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89
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Armbruster U, Pesaresi P, Pribil M, Hertle A, Leister D. Update on chloroplast research: new tools, new topics, and new trends. MOLECULAR PLANT 2011; 4:1-16. [PMID: 20924030 DOI: 10.1093/mp/ssq060] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Chloroplasts, the green differentiation form of plastids, are the sites of photosynthesis and other important plant functions. Genetic and genomic technologies have greatly boosted the rate of discovery and functional characterization of chloroplast proteins during the past decade. Indeed, data obtained using high-throughput methodologies, in particular proteomics and transcriptomics, are now routinely used to assign functions to chloroplast proteins. Our knowledge of many chloroplast processes, notably photosynthesis and photorespiration, has reached such an advanced state that biotechnological approaches to crop improvement now seem feasible. Meanwhile, efforts to identify the entire complement of chloroplast proteins and their interactions are progressing rapidly, making the organelle a prime target for systems biology research in plants.
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Affiliation(s)
- Ute Armbruster
- Lehrstuhl für Molekularbiologie der Pflanzen (Botanik), Department Biologie I, Ludwig-Maximilians-Universität München, Großhaderner Str. 2, D-82152 Planegg-Martinsried, Germany
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90
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Minagawa J. State transitions--the molecular remodeling of photosynthetic supercomplexes that controls energy flow in the chloroplast. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1807:897-905. [PMID: 21108925 DOI: 10.1016/j.bbabio.2010.11.005] [Citation(s) in RCA: 165] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2010] [Revised: 11/08/2010] [Accepted: 11/10/2010] [Indexed: 11/29/2022]
Abstract
In oxygen-evolving photosynthesis, the two photosystems-photosystem I and photosystem II-function in parallel, and their excitation levels must be balanced to maintain an optimal photosynthetic rate under natural light conditions. State transitions in photosynthetic organisms balance the absorbed light energy between the two photosystems in a short time by relocating light-harvesting complex II proteins. For over a decade, the understanding of the physiological consequences, the molecular mechanism, and its regulation has increased considerably. After providing an overview of the general understanding of state transitions, this review focuses on the recent advances of the molecular aspects of state transitions with a particular emphasis on the studies using the green alga Chlamydomonas reinhardtii. This article is part of a Special Issue entitled: Regulation of Electron Transport in Chloroplasts.
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Affiliation(s)
- Jun Minagawa
- Nattional Institute for Basic Biology, Okazaki, Japan.
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91
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Busch A, Hippler M. The structure and function of eukaryotic photosystem I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1807:864-77. [PMID: 20920463 DOI: 10.1016/j.bbabio.2010.09.009] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2010] [Revised: 09/20/2010] [Accepted: 09/28/2010] [Indexed: 12/27/2022]
Abstract
Eukaryotic photosystem I consists of two functional moieties: the photosystem I core, harboring the components for the light-driven charge separation and the subsequent electron transfer, and the peripheral light-harvesting complex (LHCI). While the photosystem I-core remained highly conserved throughout the evolution, with the exception of the oxidizing side of photosystem I, the LHCI complex shows a high degree of variability in size, subunits composition and bound pigments, which is due to the large variety of different habitats photosynthetic organisms dwell in. Besides summarizing the most current knowledge on the photosystem I-core structure, we will discuss the composition and structure of the LHCI complex from different eukaryotic organisms, both from the red and the green clade. Furthermore, mechanistic insights into electron transfer between the donor and acceptor side of photosystem I and its soluble electron transfer carrier proteins will be given. This article is part of a Special Issue entitled: Regulation of Electron Transport in Chloroplasts.
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Affiliation(s)
- Andreas Busch
- Department of Plant Biology and Biotechnology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
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92
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93
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Hohmann-Marriott MF, Takizawa K, Eaton-Rye JJ, Mets L, Minagawa J. The redox state of the plastoquinone pool directly modulates minimum chlorophyll fluorescence yield in Chlamydomonas reinhardtii. FEBS Lett 2010; 584:1021-6. [PMID: 20122933 DOI: 10.1016/j.febslet.2010.01.052] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 01/14/2010] [Accepted: 01/25/2010] [Indexed: 11/26/2022]
Abstract
The effect of the plastoquionone (PQ) pool oxidation state on minimum chlorophyll fluorescence was studied in the green alga Chlamydomonas reinhardtii. In wild type and a mutant strain that lacks both photosystems but retains light harvesting complexes, oxygen depletion induced a rise in minimum chlorophyll fluorescence. An increase in minimum fluorescence yield is also observed when the PQ pool becomes reduced in the presence of oxygen and after application of an ionophore that collapses the transmembrane proton gradient. Together these results indicate that minimum chlorophyll fluorescence is modulated by the PQ oxidation state.
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