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Gates C, Ananyev G, Foflonker F, Bhattacharya D, Dismukes GC. Exceptional Quantum Efficiency Powers Biomass Production in Halotolerant Algae Picochlorum sp. . PHOTOSYNTHESIS RESEARCH 2024:10.1007/s11120-024-01075-9. [PMID: 38329705 DOI: 10.1007/s11120-024-01075-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2023] [Accepted: 01/04/2024] [Indexed: 02/09/2024]
Abstract
The green algal genus Picochlorum is of biotechnological interest because of its robust response to multiple environmental stresses. We compared the metabolic performance of P. SE3 and P. oklahomense to diverse microbial phototrophs and observed exceptional performance of photosystem II (PSII) in light energy conversion in both Picochlorum species. The quantum yield (QY) for O2 evolution is the highest of any phototroph yet observed, 32% (20%) by P. SE3 (P. okl) when normalized to total PSII subunit PsbA (D1) protein, and 80% (75%) normalized per active PSII, respectively. Three factors contribute: (1) an efficient water oxidizing complex (WOC) with the fewest photochemical misses of any organism; (2) faster reoxidation of reduced (PQH2)B in P. SE3 than in P. okl. (period-2 Fourier amplitude); and (3) rapid reoxidation of the plastoquinol pool by downstream electron carriers (Cyt b6f/PETC) that regenerates PQ faster in P. SE3. This performance gain is achieved without significant residue changes around the QB site and thus points to a pull mechanism involving faster PQH2 reoxidation by Cyt b6f/PETC that offsets charge recombination. This high flux in P. SE3 may be explained by genomically encoded plastoquinol terminal oxidases 1 and 2, whereas P. oklahomense has neither. Our results suggest two distinct types of PSII centers exist, one specializing in linear electron flow and the other in PSII-cyclic electron flow. Several amino acids within D1 differ from those in the low-light-descended D1 sequences conserved in Viridiplantae, and more closely match those in cyanobacterial high-light D1 isoforms, including changes near tyrosine Yz and a water/proton channel near the WOC. These residue changes may contribute to the exceptional performance of Picochlorum at high-light intensities by increasing the water oxidation efficiency and the electron/proton flux through the PSII acceptors (QAQB).
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Affiliation(s)
- Colin Gates
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, New Brunswick, NJ, 08854, USA
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, NJ, 08854, USA
- Department of Computational Biology and Molecular Biophysics Rutgers, The State University of New Jersey, New Brunswick, NJ, 08854, USA
- Department of Chemistry and Biochemistry, Loyola University Chicago, Chicago, IL, 60660, USA
| | - Gennady Ananyev
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, New Brunswick, NJ, 08854, USA
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, NJ, 08854, USA
| | - Fatima Foflonker
- Department of Biochemistry and Microbiology, Rutgers, The State University of New Jersey, New Brunswick, NJ, 08854, USA
- Department of Biological Sciences, Clark Atlanta University, Atlanta, GA, 30314, USA
| | - Debashish Bhattacharya
- Department of Computational Biology and Molecular Biophysics Rutgers, The State University of New Jersey, New Brunswick, NJ, 08854, USA
| | - G Charles Dismukes
- Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, New Brunswick, NJ, 08854, USA.
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, NJ, 08854, USA.
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Gasulla F, del Campo EM, Casano LM, Guéra A. Advances in Understanding of Desiccation Tolerance of Lichens and Lichen-Forming Algae. PLANTS (BASEL, SWITZERLAND) 2021; 10:807. [PMID: 33923980 PMCID: PMC8073698 DOI: 10.3390/plants10040807] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 04/14/2021] [Accepted: 04/16/2021] [Indexed: 12/11/2022]
Abstract
Lichens are symbiotic associations (holobionts) established between fungi (mycobionts) and certain groups of cyanobacteria or unicellular green algae (photobionts). This symbiotic association has been essential in the colonization of terrestrial dry habitats. Lichens possess key mechanisms involved in desiccation tolerance (DT) that are constitutively present such as high amounts of polyols, LEA proteins, HSPs, a powerful antioxidant system, thylakoidal oligogalactolipids, etc. This strategy allows them to be always ready to survive drastic changes in their water content. However, several studies indicate that at least some protective mechanisms require a minimal time to be induced, such as the induction of the antioxidant system, the activation of non-photochemical quenching including the de-epoxidation of violaxanthin to zeaxanthin, lipid membrane remodeling, changes in the proportions of polyols, ultrastructural changes, marked polysaccharide remodeling of the cell wall, etc. Although DT in lichens is achieved mainly through constitutive mechanisms, the induction of protection mechanisms might allow them to face desiccation stress in a better condition. The proportion and relevance of constitutive and inducible DT mechanisms seem to be related to the ecology at which lichens are adapted to.
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Affiliation(s)
- Francisco Gasulla
- Department of Life Sciences, Universidad de Alcalá, Alcalá de Henares, 28802 Madrid, Spain; (E.M.d.C.); (L.M.C.)
| | | | | | - Alfredo Guéra
- Department of Life Sciences, Universidad de Alcalá, Alcalá de Henares, 28802 Madrid, Spain; (E.M.d.C.); (L.M.C.)
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Deficiency in flavodiiron protein Flv3 promotes cyclic electron flow and state transition under high light in the cyanobacterium Synechocystis sp. PCC 6803. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1862:148318. [PMID: 32979345 DOI: 10.1016/j.bbabio.2020.148318] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Revised: 09/11/2020] [Accepted: 09/19/2020] [Indexed: 11/21/2022]
Abstract
Photosynthetic organisms adjust their activity to changes in irradiance by different ways, including the operation of cyclic electron flow around photosystem I (PSI) and state transitions that redistribute amounts of light energy absorbed by PSI and PSII. In dark-acclimated wild type cells of Synechocystis PCC 6803, linear electron transport was activated after the first 500 ms of illumination, while cyclic electron flow around PSI was long predominant in the mutant deficient in flavodiiron protein Flv3. Chlorophyll P700 oxidation associated with activation of linear electron flow extended in the Flv3- mutant to several tens of seconds and included a P700+ re-reduction phase. Parallel monitoring of chlorophyll fluorescence and the redox state of P700 indicated that, at low light intensity both in wild type and in the Flv3- mutant, the transient re-reduction step coincided in time with S-M fluorescence rise, which reflected state 2-state 1 transition (Kaňa et al., 2012). Despite variations in the initial redox state of plastoquinone pool, the oxidases-deficient mutant, succinate dehydrogenase-deficient mutant, and wild type cells did not show the S-M rise under high-intensity light until additional Flv3- mutation was introduced in these strains. Thus, the lack of available electron acceptor for PSI was the main cause for the appearance of S-M fluorescence rise under high light. It is concluded that the lack of Flv3 protein promotes cyclic electron flow around PSI and facilitates the subsequent state 2-state 1 transition in the absence of strict relation to the dark-operated pathways of plastoquinone reduction or oxidation.
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Santabarbara S, Tibiletti T, Remelli W, Caffarri S. Kinetics and heterogeneity of energy transfer from light harvesting complex II to photosystem I in the supercomplex isolated from Arabidopsis. Phys Chem Chem Phys 2018; 19:9210-9222. [PMID: 28319223 DOI: 10.1039/c7cp00554g] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
State transitions are a phenomenon that maintains the excitation balance between photosystem II (PSII) and photosystem I (PSI-LHCI) by controlling their relative absorption cross-sections. Under light conditions exciting PSII preferentially, a trimeric LHCII antenna moves from PSII to PSI-LHCI to form the PSI-LHCI-LHCII supercomplex. In this work, the excited state dynamics in the PSI-LHCI and PSI-LHCI-LHCII supercomplexes isolated from Arabidopsis have been investigated by picosecond time-resolved fluorescence spectroscopy. The excited state decays were analysed using two approaches based on either (i) a sum of discrete exponentials or (ii) a continuous distribution of lifetimes. The results indicate that the energy transfer from LHCII to the bulk of the PSI antenna occurs with an average macroscopic transfer rate in the 35-65 ns-1 interval. Yet, the most satisfactory description of the data is obtained when considering a heterogeneous population containing two PSI-LHCI-LHCII supercomplexes characterised by a transfer time of ∼15 and ∼60 ns-1, likely due to the differences in the strength and orientation of LHCII harboured to PSI. Both these values are of the same order of magnitude of those estimated for the average energy transfer rates from the low energy spectral forms of LHCI to the bulk of the PSI antenna (15-40 ns-1), but they are slower than the transfer from the bulk antenna of PSI to the reaction centre (>150 ns-1), implying a relatively small kinetics bottleneck for the energy transfer from LHCII. Nevertheless, the kinetic limitation imposed by excited state diffusion has a negligible impact on the photochemical quantum efficiency of the supercomplex, which remains about 98% in the case of PSI-LHCI.
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Affiliation(s)
- Stefano Santabarbara
- Photosynthesis Research Unit, Centro di Studio per la Biologia Cellulare e Molecolare delle Piante, Via Celoria 26, 20133 Milan, Italy.
| | - Tania Tibiletti
- Aix Marseille Univ, CEA, CNRS UMR7265 BVME, Laboratoire de Génétique et Biophysique des Plantes, Marseille 13009, France
| | - William Remelli
- Photosynthesis Research Unit, Centro di Studio per la Biologia Cellulare e Molecolare delle Piante, Via Celoria 26, 20133 Milan, Italy.
| | - Stefano Caffarri
- Aix Marseille Univ, CEA, CNRS UMR7265 BVME, Laboratoire de Génétique et Biophysique des Plantes, Marseille 13009, France
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Smedbol É, Lucotte M, Labrecque M, Lepage L, Juneau P. Phytoplankton growth and PSII efficiency sensitivity to a glyphosate-based herbicide (Factor 540 ®). AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2017; 192:265-273. [PMID: 28992597 DOI: 10.1016/j.aquatox.2017.09.021] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 09/21/2017] [Accepted: 09/22/2017] [Indexed: 06/07/2023]
Abstract
The use of glyphosate-based herbicides in agriculture has increased steadily since the mid 90's and there is now evidence of glyphosate leaching and contamination of aquatic ecosystems. The aim of this study was to evaluate the effects of a glyphosate-based herbicide (Factor 540®) on growth and photosynthetic capacity of algae and cyanobacteria. Six algal and three cyanobacterial species/strains, of three different taxonomic groups, were exposed to five glyphosate concentrations (10, 50, 100, 500 and 1000μgl-1) during 48h. All species have significant growth inhibition at concentrations varying between 50 and 500μgl-1. The photosynthetic response, after glyphosate exposure, varied among species, but a general pattern has emerged. There was an increase in the amount of photons absorbed (ABS/RC), in dissipated (DIO/RC) and trapped (TRO/RC) energy in the photosystem II reaction centers, along with a decreased of the maximum photosystem II quantum yield (FV/FM) and electron transport per reaction center (ETO/RC). The EC50 and LOEC values for growth and photosynthesis were calculated and established that growth was the most affected parameter by glyphosate-based herbicide, while parameter TRO/RC was the least affected. All species showed reduced growth at glyphosate concentrations lower than the Canadian standard for the protection of aquatic life, set at 800μgl-1 or the American aquatic life benchmark for acute toxicity in non vascular plants of 12 100μgl-1 questioning the validity of these thresholds in assessing the risks related to the presence of glyphosate and glyphosate-based herbicides in aquatic systems.
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Affiliation(s)
- Élise Smedbol
- Université du Québec à Montréal, Département des Sciences biologiques - GRIL-TOXEN, Succ. Centre-Ville, C.P. 8888, H3C 3P8, Montréal, Québec, Canada; Université du Québec à Montréal, Institut des Sciences de l'environnement, Succ. Centre-Ville, C.P. 8888, H3C 3P8, Montréal, Québec, Canada
| | - Marc Lucotte
- Université du Québec à Montréal, Institut des Sciences de l'environnement, Succ. Centre-Ville, C.P. 8888, H3C 3P8, Montréal, Québec, Canada
| | - Michel Labrecque
- Université de Montréal, Institut de recherche en biologie végétale, 4101, Rue Sherbrooke Est, H1X 2B2, Montréal, Québec, Canada
| | - Laurent Lepage
- Université du Québec à Montréal, Institut des Sciences de l'environnement, Succ. Centre-Ville, C.P. 8888, H3C 3P8, Montréal, Québec, Canada
| | - Philippe Juneau
- Université du Québec à Montréal, Département des Sciences biologiques - GRIL-TOXEN, Succ. Centre-Ville, C.P. 8888, H3C 3P8, Montréal, Québec, Canada.
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Venkata Mohan S, Modestra JA, Amulya K, Butti SK, Velvizhi G. A Circular Bioeconomy with Biobased Products from CO 2 Sequestration. Trends Biotechnol 2016; 34:506-519. [DOI: 10.1016/j.tibtech.2016.02.012] [Citation(s) in RCA: 143] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Revised: 02/22/2016] [Accepted: 02/23/2016] [Indexed: 10/22/2022]
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Grieco M, Jain A, Ebersberger I, Teige M. An evolutionary view on thylakoid protein phosphorylation uncovers novel phosphorylation hotspots with potential functional implications. JOURNAL OF EXPERIMENTAL BOTANY 2016; 67:3883-96. [PMID: 27117338 DOI: 10.1093/jxb/erw164] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The regulation of photosynthetic light reactions by reversible protein phosphorylation is well established today, but functional studies have so far mostly been restricted to processes affecting light-harvesting complex II and the core proteins of photosystem II. Virtually no functional data are available on regulatory effects at the other photosynthetic complexes despite the identification of multiple phosphorylation sites. Therefore we summarize the available data from 50 published phospho-proteomics studies covering the main complexes involved in photosynthetic light reactions in the 'green lineage' (i.e. green algae and land plants) as well as its cyanobacterial counterparts. In addition, we performed an extensive orthologue search for the major photosynthetic thylakoid proteins in 41 sequenced genomes and generated sequence alignments to survey the phylogenetic distribution of phosphorylation sites and their evolutionary conservation from green algae to higher plants. We observed a number of uncharacterized phosphorylation hotspots at photosystem I and the ATP synthase with potential functional relevance as well as an unexpected divergence of phosphosites. Although technical limitations might account for a number of those differences, we think that many of these phosphosites have important functions. This is particularly important for mono- and dicot plants, where these sites might be involved in regulatory processes such as stress acclimation.
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Affiliation(s)
- Michele Grieco
- Department of Ecogenomics and Systems Biology, University of Vienna, Althanstr. 14, A-1090 Vienna, Austria
| | - Arpit Jain
- Department for Applied Bioinformatics, Institute for Cell Biology and Neuroscience, Goethe University, Max-von-Laue Str. 13, D-60438 Frankfurt, Germany
| | - Ingo Ebersberger
- Department for Applied Bioinformatics, Institute for Cell Biology and Neuroscience, Goethe University, Max-von-Laue Str. 13, D-60438 Frankfurt, Germany Senckenberg Biodiversity and Climate Research Centre (BiK-F), Senckenberg Anlage 25, D-60325 Frankfurt, Germany
| | - Markus Teige
- Department of Ecogenomics and Systems Biology, University of Vienna, Althanstr. 14, A-1090 Vienna, Austria
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Xu DQ, Chen Y, Chen GY. Light-harvesting regulation from leaf to molecule with the emphasis on rapid changes in antenna size. PHOTOSYNTHESIS RESEARCH 2015; 124:137-158. [PMID: 25773873 DOI: 10.1007/s11120-015-0115-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2014] [Accepted: 03/03/2015] [Indexed: 06/04/2023]
Abstract
In the sunlight-fluctuating environment, plants often encounter both light-deficiency and light-excess cases. Therefore, regulation of light harvesting is absolutely essential for photosynthesis in order to maximize light utilization at low light and avoid photodamage of the photosynthetic apparatus at high light. Plants have developed a series of strategies of light-harvesting regulation during evolution. These strategies include rapid responses such as leaf movement and chloroplast movement, state transitions, and reversible dissociation of some light-harvesting complex of the photosystem II (LHCIIs) from PSII core complexes, and slow acclimation strategies such as changes in the protein abundance of light-harvesting antenna and modifications of leaf morphology, structure, and compositions. This review discusses successively these strategies and focuses on the rapid change in antenna size, namely reversible dissociation of some peripheral light-harvesting antennas (LHCIIs) from PSII core complex. It is involved in protective role and species dependence of the dissociation, differences between the dissociation and state transitions, relationship between the dissociation and thylakoid protein phosphorylation, and possible mechanism for thermal dissipation by the dissociated LHCIIs.
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Affiliation(s)
- Da-Quan Xu
- Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China
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Caffarri S, Tibiletti T, Jennings RC, Santabarbara S. A comparison between plant photosystem I and photosystem II architecture and functioning. Curr Protein Pept Sci 2015; 15:296-331. [PMID: 24678674 PMCID: PMC4030627 DOI: 10.2174/1389203715666140327102218] [Citation(s) in RCA: 133] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 11/22/2013] [Accepted: 03/16/2014] [Indexed: 01/31/2023]
Abstract
Oxygenic photosynthesis is indispensable both for the development and maintenance of life on earth by converting
light energy into chemical energy and by producing molecular oxygen and consuming carbon dioxide. This latter
process has been responsible for reducing the CO2 from its very high levels in the primitive atmosphere to the present low
levels and thus reducing global temperatures to levels conducive to the development of life. Photosystem I and photosystem
II are the two multi-protein complexes that contain the pigments necessary to harvest photons and use light energy to
catalyse the primary photosynthetic endergonic reactions producing high energy compounds. Both photosystems are
highly organised membrane supercomplexes composed of a core complex, containing the reaction centre where electron
transport is initiated, and of a peripheral antenna system, which is important for light harvesting and photosynthetic activity
regulation. If on the one hand both the chemical reactions catalysed by the two photosystems and their detailed structure
are different, on the other hand they share many similarities. In this review we discuss and compare various aspects of
the organisation, functioning and regulation of plant photosystems by comparing them for similarities and differences as
obtained by structural, biochemical and spectroscopic investigations.
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Affiliation(s)
| | | | | | - Stefano Santabarbara
- Laboratoire de Génétique et de Biophysique des Plantes (LGBP), Aix-Marseille Université, Faculté des Sciences de Luminy, 163 Avenue de Luminy, 13009, Marseille, France.
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Ihnken S, Kromkamp JC, Beardall J, Silsbe GM. State-transitions facilitate robust quantum yields and cause an over-estimation of electron transport in Dunaliella tertiolecta cells held at the CO₂ compensation point and re-supplied with DIC. PHOTOSYNTHESIS RESEARCH 2014; 119:257-272. [PMID: 24135997 DOI: 10.1007/s11120-013-9937-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2013] [Accepted: 10/01/2013] [Indexed: 06/02/2023]
Abstract
Photosynthetic energy consumption and non-photosynthetic energy quenching processes are inherently linked. Both processes must be controlled by the cell to allow cell maintenance and growth, but also to avoid photodamage. We used the chlorophyte algae Dunaliella tertiolecta to investigate how the interactive regulation of photosynthetic and non-photosynthetic pathways varies along dissolved inorganic carbon (DIC) and photon flux gradients. Specifically, cells were transferred to DIC-deplete media to reach a CO₂ compensation before being re-supplied with DIC at various concentrations and different photon flux levels. Throughout these experiments we monitored and characterized the photophysiological responses using pulse amplitude modulated fluorescence, oxygen evolution, 77 K fluorescence emission spectra, and fast-repetition rate fluorometry. O₂ uptake was not significantly stimulated at DIC depletion, which suggests that O₂ production rates correspond to assimilatory photosynthesis. Fluorescence-based measures of relative electron transport rates (rETRs) over-estimated oxygen-based photosynthetic measures due to a strong state-transitional response that facilitated high effective quantum yields. Adoption of an alternative fluorescence-based rETR calculation that accounts for state-transitions resulted in improved linear oxygen versus rETR correlation. This study shows the extraordinary capacity of D. tertiolecta to maintain stable effective quantum yields by flexible regulation of state-transitions. Uncertainties about the control mechanisms of state-transitions are presented.
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Affiliation(s)
- Sven Ihnken
- Netherlands Institute for Sea Research, NIOZ, Postbus 140, 4400 AC, Yerseke, The Netherlands
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Alric J. Redox and ATP control of photosynthetic cyclic electron flow in Chlamydomonas reinhardtii: (II) involvement of the PGR5-PGRL1 pathway under anaerobic conditions. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:825-34. [PMID: 24508216 DOI: 10.1016/j.bbabio.2014.01.024] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Revised: 01/29/2014] [Accepted: 01/30/2014] [Indexed: 10/25/2022]
Abstract
In oxygenic photosynthesis, cyclic electron flow around photosystem I denotes the recycling of electrons from stromal electron carriers (reduced nicotinamide adenine dinucleotide phosphate, NADPH, ferredoxin) towards the plastoquinone pool. Whether or not cyclic electron flow operates similarly in Chlamydomonas and plants has been a matter of debate. Here we would like to emphasize that despite the regulatory or metabolic differences that may exist between green algae and plants, the general mechanism of cyclic electron flow seems conserved across species. The most accurate way to describe cyclic electron flow remains to be a redox equilibration model, while the supramolecular reorganization of the thylakoid membrane (state transitions) has little impact on the maximal rate of cyclic electron flow. The maximum capacity of the cyclic pathways is shown to be around 60 electrons transferred per photosystem per second, which is in Chlamydomonas cells treated with 3(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and placed under anoxic conditions. Part I of this work (aerobic conditions) was published in a previous issue of BBA-Bioenergetics (vol. 1797, pp. 44-51) (Alric et al., 2010).
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Affiliation(s)
- Jean Alric
- UMR 7141, CNRS et Université Pierre et Marie Curie (Paris VI), Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France.
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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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Polyphasic chlorophyll a fluorescence kinetics and leaf protein analyses to track dynamics of photosynthetic performance in mulberry during progressive drought. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2013; 119:71-83. [DOI: 10.1016/j.jphotobiol.2012.12.006] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Revised: 10/12/2012] [Accepted: 12/17/2012] [Indexed: 12/30/2022]
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Blanco-Rivero A, Shutova T, Román MJ, Villarejo A, Martinez F. Phosphorylation controls the localization and activation of the lumenal carbonic anhydrase in Chlamydomonas reinhardtii. PLoS One 2012; 7:e49063. [PMID: 23139834 PMCID: PMC3490910 DOI: 10.1371/journal.pone.0049063] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Accepted: 10/09/2012] [Indexed: 11/25/2022] Open
Abstract
Background Cah3 is the only carbonic anhydrase (CA) isoform located in the thylakoid lumen of Chlamydomonas reinhardtii. Previous studies demonstrated its association with the donor side of the photosystem II (PSII) where it is required for the optimal function of the water oxidizing complex. However this enzyme has also been frequently proposed to perform a critical function in inorganic carbon acquisition and CO2 fixation and all mutants lacking Cah3 exhibit very poor growth after transfer to low CO2 conditions. Results/Conclusions In the present work we demonstrate that after transfer to low CO2, Cah3 is phosphorylated and that phosphorylation is correlated to changes in its localization and its increase in activity. When C. reinhardtii wild-type cells were acclimated to limiting CO2 conditions, the Cah3 activity increased about 5–6 fold. Under these conditions, there were no detectable changes in the level of the Cah3 polypeptide. The increase in activity was specifically inhibited in the presence of Staurosporine, a protein kinase inhibitor, suggesting that the Cah3 protein was post-translationally regulated via phosphorylation. Immunoprecipitation and in vitro dephosphorylation experiments confirm this hypothesis. In vivo phosphorylation analysis of thylakoid polypeptides indicates that there was a 3-fold increase in the phosphorylation signal of the Cah3 polypeptide within the first two hours after transfer to low CO2 conditions. The increase in the phosphorylation signal was correlated with changes in the intracellular localization of the Cah3 protein. Under high CO2 conditions, the Cah3 protein was only associated with the donor side of PSII in the stroma thylakoids. In contrast, in cells grown at limiting CO2 the protein was partly concentrated in the thylakoids crossing the pyrenoid, which did not contain PSII and were surrounded by Rubisco molecules. Significance This is the first report of a CA being post-translationally regulated and describing phosphorylation events in the thylakoid lumen.
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Affiliation(s)
| | - Tatiana Shutova
- Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, Umeå, Sweden
| | - María José Román
- Department of Biology, Universidad Autónoma de Madrid, Madrid, Spain
| | - Arsenio Villarejo
- Department of Biology, Universidad Autónoma de Madrid, Madrid, Spain
- Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, Umeå, Sweden
| | - Flor Martinez
- Department of Biology, Universidad Autónoma de Madrid, Madrid, Spain
- * E-mail:
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Papadakis IA, Kotzabasis K, Lika K. Modeling the dynamic modulation of light energy in photosynthetic algae. J Theor Biol 2012; 300:254-64. [PMID: 22326475 DOI: 10.1016/j.jtbi.2012.01.040] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Revised: 01/26/2012] [Accepted: 01/27/2012] [Indexed: 11/27/2022]
Abstract
An integrated cell-based dynamic mathematical model that take into account the role of the photon absorbing process, the partition of excitation energy, and the photoinactivation and repair of photosynthetic units, under variable light and dissolved inorganic carbon (DIC) availability is proposed. The modeling of the photon energy absorption and the energy dissipation is based on the photoadaptive changes of the underlying mechanisms. The partition of the excitation energy is based on the relative availability of light and DIC to the cell. The modeling of the photoinactivation process is based on the common aspect that it occurs under any light intensity and the modeling of the repair process is based on the evidence that it is controlled by chloroplast and nuclear-encoded enzymes. The present model links the absorption of photons and the partitioning of excitation energy to the linear electron flow and other quenchers with chlorophyll fluorescence emission parameters, and the number of the functional photosynthetic units with the photosynthetic oxygen production rate. The energy allocation to the LEF increases as DIC availability increases and/or light intensity decreases. The rate of rejected energy increases with light intensity and with DIC availability. The resulting rate coefficient of photoinactivation increases as light intensity and/or as DIC concentration increases. We test the model against chlorophyll fluorescence induction and photosynthetic oxygen production rate measurements, obtained from cultures of the unicellular green alga Scenedesmus obliquus, and find a very close quantitative and qualitative correspondence between predictions and data.
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Affiliation(s)
- Ioannis A Papadakis
- Department of Biology, University of Crete, GR-71409, Heraklion, Crete, Greece.
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Karamoko M, Cline S, Redding K, Ruiz N, Hamel PP. Lumen Thiol Oxidoreductase1, a disulfide bond-forming catalyst, is required for the assembly of photosystem II in Arabidopsis. THE PLANT CELL 2011; 23:4462-75. [PMID: 22209765 PMCID: PMC3269877 DOI: 10.1105/tpc.111.089680] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Revised: 11/15/2011] [Accepted: 12/13/2011] [Indexed: 05/18/2023]
Abstract
Here, we identify Arabidopsis thaliana Lumen Thiol Oxidoreductase1 (LTO1) as a disulfide bond-forming enzyme in the thylakoid lumen. Using topological reporters in bacteria, we deduced a lumenal location for the redox active domains of the protein. LTO1 can partially substitute for the proteins catalyzing disulfide bond formation in the bacterial periplasm, which is topologically equivalent to the plastid lumen. An insertional mutation within the LTO1 promoter is associated with a severe photoautotrophic growth defect. Measurements of the photosynthetic activity indicate that the lto1 mutant displays a limitation in the electron flow from photosystem II (PSII). In accordance with these measurements, we noted a severe depletion of the structural subunits of PSII but no change in the accumulation of the cytochrome b(6)f complex or photosystem I. In a yeast two-hybrid assay, the thioredoxin-like domain of LTO1 interacts with PsbO, a lumenal PSII subunit known to be disulfide bonded, and a recombinant form of the molecule can introduce a disulfide bond in PsbO in vitro. The documentation of a sulfhydryl-oxidizing activity in the thylakoid lumen further underscores the importance of catalyzed thiol-disulfide chemistry for the biogenesis of the thylakoid compartment.
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Affiliation(s)
- Mohamed Karamoko
- Department of Molecular Genetics and Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio 43210
| | - Sara Cline
- Department of Molecular Genetics and Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio 43210
- Plant Cellular and Molecular Biology Graduate Program, The Ohio State University, Columbus, Ohio 43210
| | - Kevin Redding
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287
| | - Natividad Ruiz
- Department of Microbiology, The Ohio State University, Columbus, Ohio 43210
| | - Patrice P. Hamel
- Department of Molecular Genetics and Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio 43210
- Plant Cellular and Molecular Biology Graduate Program, The Ohio State University, Columbus, Ohio 43210
- Address correspondence to
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Houyoux PA, Ghysels B, Lecler R, Franck F. Interplay between non-photochemical plastoquinone reduction and re-oxidation in pre-illuminated Chlamydomonas reinhardtii: a chlorophyll fluorescence study. PHOTOSYNTHESIS RESEARCH 2011; 110:13-24. [PMID: 21948601 DOI: 10.1007/s11120-011-9686-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2009] [Accepted: 09/07/2011] [Indexed: 05/27/2023]
Abstract
In photosynthetic eukaryotes, the redox state of the plastoquinone (PQ) pool is an important sensor for mechanisms that regulate the photosynthetic electron transport. In higher plants, a multimeric nicotinamide adenine dinucleotide (phosphate) (NAD(P))H dehydrogenase (NDH) complex and a plastid terminal oxidase (PTOX) are involved in PQ redox homeostasis in the dark. We recently demonstrated that in the microalgae Chlamydomonas reinhardtii, which lacks the multimeric NDH complex of higher plants, non-photochemical PQ reduction is mediated by a monomeric type-II NDH (Nda2). In this study, we further explore the nature and the importance of non-photochemical PQ reduction and oxidation in relation to redox homeostasis in this alga by recording the 'dark' chlorophyll fluorescence transients of pre-illuminated algal samples. From the observation that this fluorescence transient is modified by addition of propyl gallate, a known inhibitor of PTOX, and in a Nda2-deficient strain we conclude that it reflects post-illumination changes in the redox state of PQ resulting from simultaneous PTOX and Nda2 activity. We show that the post-illumination fluorescence transient can be used to monitor changes in the relative rates of the non-photochemical PQ reduction and reoxidation in response to different physiological situations. We study this fluorescence transient in algae acclimated to high light and in a mutant deficient in mitochondrial respiration. Some of our observations indicate that the chlororespiratory pathway participates in redox homeostasis in C. reinhardtii.
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Affiliation(s)
- Pierre-Alain Houyoux
- Laboratory of Bioenergetics, Institute of Plant Biology B22, University of Liège, Sart Tilman, 4000 Liège, Belgium
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Cramer WA, Hasan SS, Yamashita E. The Q cycle of cytochrome bc complexes: a structure perspective. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:788-802. [PMID: 21352799 DOI: 10.1016/j.bbabio.2011.02.006] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Revised: 02/08/2011] [Accepted: 02/13/2011] [Indexed: 12/01/2022]
Abstract
Aspects of the crystal structures of the hetero-oligomeric cytochrome bc(1) and b(6)f ("bc") complexes relevant to their electron/proton transfer function and the associated redox reactions of the lipophilic quinones are discussed. Differences between the b(6)f and bc(1) complexes are emphasized. The cytochrome bc(1) and b(6)f dimeric complexes diverge in structure from a core of subunits that coordinate redox groups consisting of two bis-histidine coordinated hemes, a heme b(n) and b(p) on the electrochemically negative (n) and positive (p) sides of the complex, the high potential [2Fe-2S] cluster and c-type heme at the p-side aqueous interface and aqueous phase, respectively, and quinone/quinol binding sites on the n- and p-sides of the complex. The bc(1) and b(6)f complexes diverge in subunit composition and structure away from this core. b(6)f Also contains additional prosthetic groups including a c-type heme c(n) on the n-side, and a chlorophyll a and β-carotene. Common structure aspects; functions of the symmetric dimer. (I) Quinone exchange with the bilayer. An inter-monomer protein-free cavity of approximately 30Å along the membrane normal×25Å (central inter-monomer distance)×15Å (depth in the center), is common to both bc(1) and b(6)f complexes, providing a niche in which the lipophilic quinone/quinol (Q/QH(2)) can be exchanged with the membrane bilayer. (II) Electron transfer. The dimeric structure and the proximity of the two hemes b(p) on the electrochemically positive side of the complex in the two monomer units allow the possibility of two alternate routes of electron transfer across the complex from heme b(p) to b(n): intra-monomer and inter-monomer involving electron cross-over between the two hemes b(p). A structure-based summary of inter-heme distances in seven bc complexes, representing mitochondrial, chromatophore, cyanobacterial, and algal sources, indicates that, based on the distance parameter, the intra-monomer pathway would be favored kinetically. (III) Separation of quinone binding sites. A consequence of the dimer structure and the position of the Q/QH(2) binding sites is that the p-side QH(2) oxidation and n-side Q reduction sites are each well separated. Therefore, in the event of an overlap in residence time by QH(2) or Q molecules at the two oxidation or reduction sites, their spatial separation would result in minimal steric interference between extended Q or QH(2) isoprenoid chains. (IV) Trans-membrane QH(2)/Q transfer. (i) n/p-side QH(2)/Q transfer may be hindered by lipid acyl chains; (ii) the shorter less hindered inter-monomer pathway across the complex would not pass through the center of the cavity, as inferred from the n-side antimycin site on one monomer and the p-side stigmatellin site on the other residing on the same surface of the complex. (V) Narrow p-side portal for QH(2)/Q passage. The [2Fe-2S] cluster that serves as oxidant, and whose histidine ligand serves as a H(+) acceptor in the oxidation of QH(2), is connected to the inter-monomer cavity by a narrow extended portal, which is also occupied in the b(6)f complex by the 20 carbon phytyl chain of the bound chlorophyll.
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Affiliation(s)
- William A Cramer
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
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Alric J. Cyclic electron flow around photosystem I in unicellular green algae. PHOTOSYNTHESIS RESEARCH 2010; 106:47-56. [PMID: 20532629 DOI: 10.1007/s11120-010-9566-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2010] [Accepted: 05/24/2010] [Indexed: 05/02/2023]
Abstract
Cyclic electron flow around PSI, or cyclic photophosphorylation, is the photosynthetic process which recycles the reducing equivalents produced by photosystem I in the stroma towards the plastoquinone pool. Through the activity of cytochrome b(6)f, which also transfers protons across the membrane, it promotes the synthesis of ATP. The literature dealing with cyclic electron flow in unicellular algae is far less abundant than it is for plants. However, in the chloroplast of algae such as Chlorella or Chlamydomonas, an efficient carbohydrate catabolism renders the redox poise much more reducing than in plant chloroplasts. It is therefore worthwhile highlighting the specific properties of unicellular algae because cyclic electron flow is highly dependent upon the accumulation of these stromal reducing equivalents. Such an increase of reducing power in the stroma stimulates the reduction of plastoquinones, which is the limiting step of cyclic electron flow. In anaerobic conditions in the dark, this reaction can lead to a fully reduced plastoquinone pool and induce state transitions, the migration of 80% of light harvesting complexes II and 20% of cytochrome b(6)f complex from the PSII-enriched grana to the PSI-enriched lamella. These ultrastructural changes have been proposed to further enhance cyclic electron flow by increasing PSI antenna size, and forming PSI-cyt b(6)f supercomplexes. These hypotheses are discussed in light of recently published data.
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Affiliation(s)
- Jean Alric
- UMR 7141, CNRS et Université Pierre et Marie Curie (Paris VI), Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France.
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Tsunoyama Y, Bernát G, Dyczmons NG, Schneider D, Rögner M. Multiple Rieske proteins enable short- and long-term light adaptation of Synechocystis sp. PCC 6803. J Biol Chem 2009; 284:27875-27883. [PMID: 19674969 PMCID: PMC2788838 DOI: 10.1074/jbc.m109.011189] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2009] [Revised: 08/12/2009] [Indexed: 11/06/2022] Open
Abstract
In contrast to eukaryotes, most cyanobacteria contain several isoforms of the Rieske iron-sulfur protein, PetC, resulting in heterogeneity in the composition of the cytochrome b(6)f complexes. Of three isoforms in the mesophilic cyanobacterium Synechocystis PCC 6803, PetC1 is the major Rieske protein in the cytochrome b(6)f complex, whereas the physiological function of PetC2 and PetC3 is still uncertain. Comparison of wild type and various petC-deficient strains under selected light conditions revealed distinct functional differences: high-light exposure of wild type cells resulted in a significantly enhanced petC2 transcript level, whereas a Delta petC1 mutant showed a low cytochrome b(6)f content, low electron flux, and a considerably increased accumulation of cytochrome-bd oxidase. In contrast to wild type and Delta petC1, Delta petC2 and Delta petC3 strains still grew fast under high-light conditions although all three Rieske proteins are required for maximal electron transport rates. Although the presence of PetC3 appears to be required for activation of the cyclic electron transport, state transitions were more effective in the absence of PetC2 and/or PetC3. In summary, our data suggest defined roles of the various PetC proteins in short- and long-term light adaptation.
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Affiliation(s)
- Yuichi Tsunoyama
- Department of Plant Biochemistry, Ruhr-University Bochum, 44780 Bochum, Germany; Division of Biology, Radioisotope Research Center, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Gábor Bernát
- Department of Plant Biochemistry, Ruhr-University Bochum, 44780 Bochum, Germany
| | - Nina G Dyczmons
- Department of Plant Biochemistry, Ruhr-University Bochum, 44780 Bochum, Germany
| | - Dirk Schneider
- Department of Biochemistry and Molecular Biology, ZBMZ, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany
| | - Matthias Rögner
- Department of Plant Biochemistry, Ruhr-University Bochum, 44780 Bochum, Germany.
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Langner U, Jakob T, Stehfest K, Wilhelm C. An energy balance from absorbed photons to new biomass for Chlamydomonas reinhardtii and Chlamydomonas acidophila under neutral and extremely acidic growth conditions. PLANT, CELL & ENVIRONMENT 2009; 32:250-258. [PMID: 19054351 DOI: 10.1111/j.1365-3040.2008.01917.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Chlamydomonas is one of the most well-studied photosynthetic organisms that had important biotechnological potential for future bioproductions of biofuels. However, an energy balance from incident photons to the energy stored in the new biomass is still lacking. In this study, we applied a recently developed system to measure the energy balance for steady state growth of Chlamydomonas reinhardtii grown at pH 6.5, and C. acidophila that was grown at pH 6.5 and 2.6. Energy use efficiency was quantified on the basis of light absorption, photosynthetic quantum yield, photosynthetic and respiratory quotient, and electron partitioning into proteins, carbohydrates and lipids. The results showed that lower growth rates of C. acidophila under both pH conditions were not caused by the differences in the photosynthetic quantum yield or in alternative electron cycling, but rather by differences in the efficiency of light absorption and increased dark respiration. Analysis of the macromolecular composition of the cells during the light phase showed that C. acidophila uses biosynthetic electrons preferentially for carbohydrate synthesis but not for synthesis of lipids. This led to a strong diurnal cycle of the C/N ratio and could explain the higher dark respiration of C. acidophila compared with C. reinhardtii.
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Affiliation(s)
- Uwe Langner
- University of Leipzig, Institute of Biology I, Department of Plant Physiology, Leipzig, Germany
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Abstract
Despite recent elucidation of the three-dimensional structure of major photosynthetic complexes, our understanding of light energy conversion in plant chloroplasts and microalgae under physiological conditions requires exploring the dynamics of photosynthesis. The photosynthetic apparatus is a flexible molecular machine that can acclimate to metabolic and light fluctuations in a matter of seconds and minutes. On a longer time scale, changes in environmental cues trigger acclimation responses that elicit intracellular signaling between the nucleo-cytosol and chloroplast resulting in modification of the biogenesis of the photosynthetic machinery. Here we attempt to integrate well-established knowledge on the functional flexibility of light-harvesting and electron transfer processes, which has greatly benefited from genetic approaches, with data derived from the wealth of recent transcriptomic and proteomic studies of acclimation responses in photosynthetic eukaroytes.
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Affiliation(s)
- Stephan Eberhard
- Université Pierre et Marie Curie, Institut de Biologie Physico-Chimique, F-75005 Paris, France
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Kargul J, Barber J. Photosynthetic acclimation: Structural reorganisation of light harvesting antenna - role of redox-dependent phosphorylation of major and minor chlorophyll a/b binding proteins. FEBS J 2008; 275:1056-68. [DOI: 10.1111/j.1742-4658.2008.06262.x] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Park W, Moon I. A discrete multi states model for the biological production of hydrogen by phototrophic microalga. Biochem Eng J 2007. [DOI: 10.1016/j.bej.2006.06.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Yamashita E, Zhang H, Cramer WA. Structure of the cytochrome b6f complex: quinone analogue inhibitors as ligands of heme cn. J Mol Biol 2007; 370:39-52. [PMID: 17498743 PMCID: PMC1993820 DOI: 10.1016/j.jmb.2007.04.011] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2007] [Revised: 04/01/2007] [Accepted: 04/04/2007] [Indexed: 11/24/2022]
Abstract
A native structure of the cytochrome b(6)f complex with improved resolution was obtained from crystals of the complex grown in the presence of divalent cadmium. Two Cd(2+) binding sites with different occupancy were determined: (i) a higher affinity site, Cd1, which bridges His143 of cytochrome f and the acidic residue, Glu75, of cyt b(6); in addition, Cd1 is coordinated by 1-2 H(2)O or 1-2 Cl(-); (ii) a second site, Cd2, of lower affinity for which three identified ligands are Asp58 (subunit IV), Glu3 (PetG subunit) and Glu4 (PetM subunit). Binding sites of quinone analogue inhibitors were sought to map the pathway of transfer of the lipophilic quinone across the b(6)f complex and to define the function of the novel heme c(n). Two sites were found for the chromone ring of the tridecyl-stigmatellin (TDS) quinone analogue inhibitor, one near the p-side [2Fe-2S] cluster. A second TDS site was found on the n-side of the complex facing the quinone exchange cavity as an axial ligand of heme c(n). A similar binding site proximal to heme c(n) was found for the n-side inhibitor, NQNO. Binding of these inhibitors required their addition to the complex before lipid used to facilitate crystallization. The similar binding of NQNO and TDS as axial ligands to heme c(n) implies that this heme utilizes plastoquinone as a natural ligand, thus defining an electron transfer complex consisting of hemes b(n), c(n), and PQ, and the pathway of n-side reduction of the PQ pool. The NQNO binding site explains several effects associated with its inhibitory action: the negative shift in heme c(n) midpoint potential, the increased amplitude of light-induced heme b(n) reduction, and an altered EPR spectrum attributed to interaction between hemes c(n) and b(n). A decreased extent of heme c(n) reduction by reduced ferredoxin in the presence of NQNO allows observation of the heme c(n) Soret band in a chemical difference spectrum.
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Abstract
Crystal structures and their implications for function are described for the energy transducing hetero-oligomeric dimeric cytochrome b6f complex of oxygenic photosynthesis from the thermophilic cyanobacterium, Mastigocladus laminosus, and the green alga, Chlamydomonas reinhardtii. The complex has a cytochrome b core and a central quinone exchange cavity, defined by the two monomers that are very similar to those in the respiratory cytochrome bc1 complex. The pathway of quinol/quinone (Q/QH2) transfer emphasizes the labyrinthine internal structure of the complex, including an 11x12 A portal through which Q/QH2, containing a 45-carbon isoprenoid chain, must pass. Three prosthetic groups are present in the b6f complex that are not found in the related bc1 complex: a chlorophyll (Chl) a, a beta-carotene, and a structurally unique covalently bound heme that does not possess amino acid side chains as axial ligands. It is hypothesized that this heme, exposed to the cavity and a neighboring plastoquinone and close to the positive surface potential of the complex, can function in cyclic electron transport via anionic ferredoxin.
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Affiliation(s)
- William A Cramer
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2054, USA.
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Szyszka B, Ivanov AG, Hüner NPA. Psychrophily is associated with differential energy partitioning, photosystem stoichiometry and polypeptide phosphorylation in Chlamydomonas raudensis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1767:789-800. [PMID: 17234152 DOI: 10.1016/j.bbabio.2006.12.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2006] [Revised: 11/23/2006] [Accepted: 12/03/2006] [Indexed: 11/29/2022]
Abstract
Chlamydomonas raudensis UWO 241 and SAG 49.72 represent the psychrophilic and mesophilic strains of this green algal species. This novel discovery was exploited to assess the role of psychrophily in photoacclimation to growth temperature and growth irradiance. At their optimal growth temperatures of 8 degrees C and 28 degrees C respectively, UWO 241 and SAG 49.72 maintained comparable photostasis, that is energy balance, as measured by PSII excitation pressure. Although UWO 241 exhibited higher excitation pressure, measured as 1-qL, at all growth light intensities, the relative changes in 1-qL were similar to that of SAG 49.72 in response to growth light. In response to suboptimal temperatures and increased growth irradiance, SAG 49.72 favoured energy partitioning of excess excitation energy through inducible, down regulatory processes (Phi(NPQ)) associated with the xanthophyll cycle and antenna quenching, while UWO 241 favoured xanthophyll cycle-independent energy partitioning through constitutive processes involved in energy dissipation (Phi(NO)). In contrast to SAG 49.72, an elevation in growth temperature induced an increase in PSI/PSII stoichiometry in UWO 241. Furthermore, SAG 49.72 showed typical threonine-phosphorylation of LHCII, whereas UWO 241 exhibited phosphorylation of polypeptides of comparable molecular mass to PSI reaction centres but the absence of LHCII phosphorylation. Thus, although both strains maintain an energy balance irrespective of their differences in optimal growth temperatures, the mechanisms used to maintain photostasis were distinct. We conclude that psychrophily in C. raudensis is complex and appears to involve differential energy partitioning, photosystem stoichiometry and polypeptide phosphorylation.
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Affiliation(s)
- Beth Szyszka
- Department of Biology and The Biotron, University of Western Ontario, 1151 Richmond Street N., London, Ontario, Canada
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Ali K, Santabarbara S, Heathcote P, Evans MCW, Purton S. Bidirectional electron transfer in photosystem I: Replacement of the symmetry-breaking tryptophan close to the PsaB-bound phylloquinone (A1B) with a glycine residue alters the redox properties of A1B and blocks forward electron transfer at cryogenic temperatures. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1757:1623-33. [PMID: 16989769 DOI: 10.1016/j.bbabio.2006.07.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2006] [Revised: 07/14/2006] [Accepted: 07/24/2006] [Indexed: 11/25/2022]
Abstract
A conserved tryptophan residue located between the A(1B) and F(X) redox centres on the PsaB side of the Photosystem I reaction centre has been mutated to a glycine in Chlamydomonas reinhardtii, thereby matching the conserved residue found in the equivalent position on the PsaA side. This mutant (PsaB:W669G) was studied using EPR spectroscopy with a view to understanding the molecular basis of the reported kinetic differences in forward electron transfer from the A(1A) and the A(1B) phyllo(semi)quinones. The kinetics of A(1)(-) reoxidation due to forward electron transfer or charge recombination were measured by electron spin echo spectroscopy at 265 K and 100 K, respectively. At 265 K, the reoxidation kinetics are considerably lengthened in the mutant in comparison to the wild-type. Under conditions in which F(X) is initially oxidised the kinetics of charge recombination at 100 K are found to be biphasic in the mutant while they are substantially monophasic in the wild-type. Pre-reduction of F(X) leads to biphasic kinetics in the wild-type, but does not alter the already biphasic kinetic properties of the PsaB:W669G mutant. Reduction of the [4Fe-4S] clusters F(A) and F(B) by illumination at 15 K is suppressed in the mutant. The results provide further support for the bi-directional model of electron transfer in Photosystem I of C. reinhardtii, and indicate that the replacement of the tryptophan residue with glycine mainly affects the redox properties of the PsaB bound phylloquinone A(1B).
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Affiliation(s)
- Kulsam Ali
- Department of Biology, University College London, Gower Street, London WC1E 6BT, UK
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Cramer WA, Zhang H. Consequences of the structure of the cytochrome b6f complex for its charge transfer pathways. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1757:339-45. [PMID: 16787635 DOI: 10.1016/j.bbabio.2006.04.020] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2006] [Revised: 03/30/2006] [Accepted: 04/24/2006] [Indexed: 11/17/2022]
Abstract
At least two features of the crystal structures of the cytochrome b6f complex from the thermophilic cyanobacterium, Mastigocladus laminosus and a green alga, Chlamydomonas reinhardtii, have implications for the pathways and mechanism of charge (electron/proton) transfer in the complex: (i) The narrow 11 x 12 A portal between the p-side of the quinone exchange cavity and p-side plastoquinone/quinol binding niche, through which all Q/QH2 must pass, is smaller in the b6f than in the bc1 complex because of its partial occlusion by the phytyl chain of the one bound chlorophyll a molecule in the b6f complex. Thus, the pathway for trans-membrane passage of the lipophilic quinone is even more labyrinthine in the b6f than in the bc1 complex. (ii) A unique covalently bound heme, heme cn, in close proximity to the n-side b heme, is present in the b6f complex. The b6f structure implies that a Q cycle mechanism must be modified to include heme cn as an intermediate between heme bn and plastoquinone bound at a different site than in the bc1 complex. In addition, it is likely that the heme bn-cn couple participates in photosytem I-linked cyclic electron transport that requires ferredoxin and the ferredoxin: NADP+ reductase. This pathway through the n-side of the b6f complex could overlap with the n-side of the Q cycle pathway. Thus, either regulation is required at the level of the redox state of the hemes that would allow them to be shared by the two pathways, and/or the two different pathways are segregated in the membrane.
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Affiliation(s)
- William A Cramer
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
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Su JH, Shen YK. Influence of state-2 transition on the proton motive force across the thylakoid membrane in spinach chloroplasts. PHOTOSYNTHESIS RESEARCH 2005; 85:235-45. [PMID: 16075323 DOI: 10.1007/s11120-005-4619-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2004] [Accepted: 03/29/2005] [Indexed: 05/03/2023]
Abstract
The proton motive force (pmf) across the thylakoid membrane is composed of the proton gradient and the membrane potential, which promotes millisecond-delayed light emission (ms-DLE). In this study, the time courses of LHC II phosphorylation and ms-DLE were investigated in spinach chloroplast during State-2 transition. Red light illumination resulted in an exponential rise in LHC II phosphorylation and a biphasic time course of ms-DLE. The phospho-LHC II appeared upon approximately 1 min illumination. The phosphorylation level increased exponentially when illumination was elongated to 20 min. The t((1/2) )of saturated LHC II phosphorylation was estimated 4-5 min under present illumination. During this process, the amplitudes of ms-DLE increased transiently to a maximal amplitude within 0.5 min illumination, and the reached maximum of the fast phase of ms-DLE was approximately 140% of the dark control. Then, ms-DLE decreased from the maximum. After > or =3 min illumination, ms-DLE decreased to a lower level than the dark control. In the presence of uncouplers and inhibitors, the transient increase in the biphasic time course of ms-DLE was removed by nigericin and DCMU, and the sequential decrease was delayed by DCCD. The time course was not affected significantly by valinomycin and DBMIB. Moreover, the level of LHC II phosphorylation was enhanced by nigericin, valinomycin and DCCD, and was inhibited completely by DCMU and partially by DBMIB. Taken together, we proposed that the PS II photochemical activity remained unaffected even with a higher level of LHC II phosphorylation, which was reflected by the effect of DCCD on the time course of ms-DLE. Probably, the evidence of LHC II phosphorylation is the rearrangement of LHC II-PS II complex and the thylakoid, a feedback to light-exposure, rather than the redistribution of excitation energy from PS II to PS I.
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Affiliation(s)
- Ji-Hu Su
- Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences.
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