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1.
Yuichiro Takahashi 《Journal of plant research》1998,111(1):101-111
The photosystem I, photosystem II, and cytochromeb
6
f complexes that are involved in electron transport of oxygenic photosynthesis consist of a number of subunits encoded by either
the chloroplast or nuclear genomes. In addition to the major subunits that carry redox components or photosynthetic pigments,
these complexes contain several to more than ten subunits with molecular masses of less than 10 kDa. Directed mutagenesis
has served as a powerful tool for investigation of the roles of these small subunits in the organization or function of the
complexes. Various chloroplast transformants of the green algaChlamydomonas reinhardtii and mutants of cyanobacteria in which a gene encoding a small subunit was deleted or altered have been constructed. Evidence
has accumulated suggesting that these small subunits function in the assembly, stabilization, or protection from photoinhibition
of the complexes or in the modulation or regulation of electron transport. This article presents an overview of the properties
and functions of the chloroplast-encoded small subunits of the three multiprotein complexes of photosynthetic electron transport
that have been mainly analyzed with chloroplast transformants ofC. reinhardtii and the corresponding cyanobacterial transformants.
Recipient of the Botanical Society Award for Young Scientists, 1995. 相似文献
2.
3.
In this study, we evaluated how cadmium inhibitory effect on photosystem II and I electron transport may affect light energy
conversion into electron transport by photosystem II. To induce cadmium effect on the photosynthetic apparatus, we exposed
Chlamydomonas reinhardtii 24 h to 0–4.62 μM Cd2+. By evaluating the half time of fluorescence transients O–J–I–P at different temperatures (20–30°C), we were able to determine
the photosystem II apparent activation energies for different reduction steps of photosystem II, indicated by the O–J–I–P
fluorescence transients. The decrease of the apparent activation energies for PSII electron transport was found to be strongly
related to the cadmium-induced inhibition of photosynthetic electron transport. We found a strong correlation between the
photosystem II apparent activation energies and photosystem II oxygen evolution rate and photosystem I activity. Different
levels of cadmium inhibition at photosystem II water-splitting system and photosystem I activity showed that photosystem II
apparent activation energies are strongly dependent to photosystem II donor and acceptor sides. Therefore, the oxido-reduction
state of whole photosystem II and I electron transport chain affects the conversion of light energy from antenna complex to
photosystem II electron transport. 相似文献
4.
Boris V. Trubitsin Olga A. Koksharova Liya A. Vitukhnovskaya Alexey Yu. Semenov 《BBA》2005,1708(2):238-249
In this work, we investigated electron transport processes in the cyanobacterium Synechocystis sp. PCC 6803, with a special emphasis focused on oxygen-dependent interrelations between photosynthetic and respiratory electron transport chains. Redox transients of the photosystem I primary donor P700 and oxygen exchange processes were measured by the EPR method under the same experimental conditions. To discriminate between the factors controlling electron flow through photosynthetic and respiratory electron transport chains, we compared the P700 redox transients and oxygen exchange processes in wild type cells and mutants with impaired photosystem II and terminal oxidases (CtaI, CydAB, CtaDEII). It was shown that the rates of electron flow through both photosynthetic and respiratory electron transport chains strongly depended on the transmembrane proton gradient and oxygen concentration in cell suspension. Electron transport through photosystem I was controlled by two main mechanisms: (i) oxygen-dependent acceleration of electron transfer from photosystem I to NADP+, and (ii) slowing down of electron flow between photosystem II and photosystem I governed by the intrathylakoid pH. Inhibitor analysis of P700 redox transients led us to the conclusion that electron fluxes from dehydrogenases and from cyclic electron transport pathway comprise 20-30% of the total electron flux from the intersystem electron transport chain to P700+. 相似文献
5.
Hager M Hermann M Biehler K Krieger-Liszkay A Bock R 《The Journal of biological chemistry》2002,277(16):14031-14039
Photosystem II is a large pigment-protein complex catalyzing water oxidation and initiating electron transfer processes across the thylakoid membrane. In addition to large protein subunits, many of which bind redox cofactors, photosystem II particles contain a number of low molecular weight polypeptides whose function is only poorly defined. Here we have investigated the function of one of the smallest polypeptides in photosystem II, PsbJ. Using a reverse genetics approach, we have inactivated the psbJ gene in the tobacco chloroplast genome. We show that, although the PsbJ polypeptide is not principally required for functional photosynthetic electron transport, plants lacking PsbJ are unable to grow photoautotrophically. We provide evidence that this is due to the accumulation of incompletely assembled water-splitting complexes, which in turn causes drastically reduced photosynthetic performance and extreme hypersensitivity to light. Our results suggest a role of PsbJ for the stable assembly of the water-splitting complex of photosystem II and, in addition, support a control of photosystem I accumulation through photosystem II activity. 相似文献
6.
Proposals for the naming of chloroplast genes. II. Update to the nomenclature of genes for thylakoid membrane polypeptides 总被引:1,自引:1,他引:0
Richard B. Hallick 《Plant Molecular Biology Reporter》1989,7(4):266-275
The nomenclature for genes for components of the photosynthetic membranes has been reviewed and updated. Newly discovered
genes have been added to the existing convention for gene nomenclature. Genes designatedpetA throughpetI are described for components of the photosynthetic electron transport systems,psaA throughpsaK for photosystem I components, andpsbA throughpsbR for photosystem II, including the extrinsic polypeptides of the oxygen-evolving complex. References for representative examples
of each gene are given. 相似文献
7.
Four different photosynthetic mutants of Euglena gracilis were characterized as to their lesions in photosynthetic electron transport. Two were defective around photosystem II: one, in electron transport on the oxidizing side of photosystem II, and the second lacked cytochrome 558. The location of the defect in the third mutant was concluded to be in the carbon fixation cycle, since it could catalyse both photosynthetic electron transport and photophosphorylation. The fourth mutant had a defect in its mechanism of photophosphorylation. 相似文献
8.
Summary A review is given of primary and associated electron transport reactions in various division of photosynthetic bacteria and in the two photosystems of plant photosynthesis. Two types of electron acceptor chains are distinguished: type Q, found in purple bacteria, Chloroflexus and system II of oxygenic photosynthesis and type F, found in green sulfur bacteria, Heliobacterium and photosystem I. Secondary donor reactions are discussed in relation to plant photosystem II.Dedicated to the memory of Warren L. Butler 相似文献
9.
Chloroplast transformation of Chlamydomonas reinhardtii has developed into a powerful tool for studying the structure, function and assembly of thylakoid protein complexes in a eukaryotic organism. In this article we review the progress that is being made in the development of procedures for efficient chloroplast transformation. This focuses on the development of selectable markers and the use of Chlamydomonas mutants, individually lacking thylakoid protein complexes, as recipients. Chloroplast transformation has now been used to engineer all four major thylakoid protein complexes, photosystem II, photosystem I, cytochrome b
6/f and ATP synthase. These results are discussed with an emphasis on new insights into assembly and function of these complexes in chloroplasts as compared with their prokaryotic counterparts.Abbreviations ENDOR
electron nuclear double resonance
- ESEEM
electron spin echo envelope modulation
- LHC
light harvesting complex
- PSI
Photosystem I
- PS II
Photosystem II
- P680
primary electron donor in PS II
- P700
primary electron donor in PS I 相似文献
10.
Shaun Bailey Anastasios Melis Pierre Cardol Giovanni Finazzi Gry Mine Berg Jeff Shrager 《BBA》2008,1777(3):269-276
Cyanobacteria dominate the world's oceans where iron is often barely detectable. One manifestation of low iron adaptation in the oligotrophic marine environment is a decrease in levels of iron-rich photosynthetic components, including the reaction center of photosystem I and the cytochrome b6f complex [R.F. Strzepek and P.J. Harrison, Photosynthetic architecture differs in coastal and oceanic diatoms, Nature 431 (2004) 689-692.]. These thylakoid membrane components have well characterised roles in linear and cyclic photosynthetic electron transport and their low abundance creates potential impediments to photosynthetic function. Here we show that the marine cyanobacterium Synechococcus WH8102 exhibits significant alternative electron flow to O2, a potential adaptation to the low iron environment in oligotrophic oceans. This alternative electron flow appears to extract electrons from the intersystem electron transport chain, prior to photosystem I. Inhibitor studies demonstrate that a propyl gallate-sensitive oxidase mediates this flow of electrons to oxygen, which in turn alleviates excessive photosystem II excitation pressure that can often occur even at relatively low irradiance. These findings are also discussed in the context of satisfying the energetic requirements of the cell when photosystem I abundance is low. 相似文献
11.
Functional size of photosynthetic electron transport chain determined by radiation inactivation 总被引:1,自引:1,他引:0
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Radiation inactivation technique was employed to determine the functional size of photosynthetic electron transport chain of spinach chloroplasts. The functional size for photosystem I+II (H2O to methylviologen) was 623 ± 37 kilodaltons; for photosystem II (H2O to dimethylquinone/ferricyanide), 174 ± 11 kilodaltons; and for photosystem I (reduced diaminodurene to methylviologen), 190 ± 11 kilodaltons. The difference between 364 ± 22 (the sum of 174 ± 11 and 190 ± 11) kilodaltons and 623 ± 37 kilodaltons is partially explained to be due to the presence of two molecules of cytochrome b6/f complex of 280 kilodaltons. The molecular mass for other partial reactions of photosynthetic electron flow, also measured by radiation inactivation, is reported. The molecular mass obtained by this technique is compared with that determined by other conventional biochemical methods. A working hypothesis for the composition, stoichiometry, and organization of polypeptides for photosynthetic electron transport chain is proposed. 相似文献
12.
Riethmuller-Haage I Bastiaans L Harbinson J Kempenaar C Kropff MJ 《Photosynthesis research》2006,88(3):331-341
The influence of the acetolactate synthase inhibitor metsulfuron-methyl on the operation of the photosynthetic apparatus was examined on 4-weeks-old climate chamber-grown Solanum nigrum plant. To have an indication on the relative performance of the photosynthetic apparatus of ALS-treated plants, the level of carbon dioxide (CO2) fixation, the relative quantum efficiency of photosystem I (ΦPSI) or photosystem II (ΦPSII) electron transport and leaf chlorophyll content were assessed for both control and treated plants at 2, 4 and 7 days after application of the herbicide. Results indicated a progressive inhibition of the level of CO2 fixation, the relative quantum efficiency of photosystem I (ФPSI) and II (ФPSII) electron transport and the leaf chlorophyll content already 2 days after application of the herbicide. The linear relationship between the photosystem I and II was unaltered by herbicidal treatment and was sustained under conditions where large changes in pigment composition of the leaves occurred. It appears that the stress-induced loss of leaf chlorophyll is not a catastrophic process but rather is the consequence of a well-organised breakdown of components. Under photorespiratory and non-photorespiratory conditions, the relationship between the index of electron transport flow through photosystem I and II and the rate of CO2 fixation is altered so that electron transport becomes less efficient at driving CO2 fixation. 相似文献
13.
The mechanism by which suspension medium ions regulate the rate of photoinduced electron transport across photosystem II was investigated with ion permeabilized cells of the cyanobacterium Anacystis
nidulans. Electron transport was measured as the reduction of the electroneutral acceptor dichlorophenol indophenol, whose surface concentration is independent of electrostatic membrane potential. Potassium salts stimulate photoinduced electron transport at low concentrations and inhibit it at higher concentrations. No inhibition is observed when an antichaotropic anion is associated with potassium, while the inhibition is more severe the stronger the chaotropic character of the anion. Neutralization of the surface charge by potassium ions ligated to negatively charged membrane sites at the cytoplasmic side is a prerequisite for the expression of the chaotropic inhibition of photosystem II electron transport.Abbreviations Chl
chlorophyll
- DCIP
2,6-dichlorophenol indophenol
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethyl urea
- DPC
1,5-diphenyl carbazide
- FeCN
ferricyanide anion
- Hepes
4-(2-hydroxyethyl)-1-piperazine ethanesulfonic acid
- PS
photosystem
- TEC3+
tris ethylene diamine cobalt cation 相似文献
14.
Electron Transport through photosystem I Stimulates Light Activation of Ribulose Bisphosphate Carboxylase/Oxygenase (Rubisco) by Rubisco Activase 总被引:2,自引:1,他引:1
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The activation state of ribulose bisphosphate carboxylase/oxygenase (rubisco) in a lysed chloroplast system is increased by light in the presence of a saturating concentration of ATP and a physiological concentration of CO2 (10 micromolar). Electron transport inhibitors and artificial electron donors and acceptors were used to determine in which region of the photosynthetic electron transport chain this light-dependent reaction occurred. In the presence of DCMU and methyl viologen, the artificial donors durohydroquinone and 2,6-dichlorophenolindophenol (DCPIP) plus ascorbate both supported light activation of rubisco at saturating ATP concentrations. No light activation occurred when DCPIP was used as an acceptor with water as electron donor in the presence of ATP and dibromothymoquinone, even though photosynthetic electron transport was observed. Nigericin completely inhibited the light-dependent activation of rubisco. Based on these results, we conclude that stimulation of light activation of rubisco by rubisco activase requires electron transport through PSI but not PSII, and that this light requirement is not to supply the ATP needed by the rubisco activase reaction. Furthermore, a pH gradient across the thylakoid membrane appears necessary for maximum light activation of rubisco even when ATP is provided exogenously. 相似文献
15.
Acclimation to high-light conditions in cyanobacteria: from gene expression to physiological responses 总被引:2,自引:0,他引:2
Photosynthetic organisms have evolved various acclimatory responses to high-light (HL) conditions to maintain a balance between
energy supply (light harvesting and electron transport) and consumption (cellular metabolism) and to protect the photosynthetic
apparatus from photodamage. The molecular mechanism of HL acclimation has been extensively studied in the unicellular cyanobacterium
Synechocystis sp. PCC 6803. Whole genome DNA microarray analyses have revealed that the change in gene expression profile under HL is closely
correlated with subsequent acclimatory responses such as (1) acceleration in the rate of photosystem II turnover, (2) downregulation
of light harvesting capacity, (3) development of a protection mechanism for the photosystems against excess light energy,
(4) upregulation of general protection mechanism components, and (5) regulation of carbon and nitrogen assimilation. In this
review article, we survey recent progress in the understanding of the molecular mechanisms of these acclimatory responses
in Synechocystis sp. PCC 6803. We also briefly describe attempts to understand HL acclimation in various cyanobacterial species in their natural
environments. 相似文献
16.
THOMAS D. SHARKEY 《Plant, cell & environment》2005,28(3):269-277
Photosynthesis is particularly sensitive to heat stress and recent results provide important new insights into the mechanisms by which moderate heat stress reduces photosynthetic capacity. Perhaps most surprising is that there is little or no damage to photosystem II as a result of moderate heat stress even though moderate heat stress can reduce the photosynthetic rate to near zero. Moderate heat stress can stimulate dark reduction of plastoquinone and cyclic electron flow in the light. In addition, moderate heat stress may increase thylakoid leakiness. At the same time, rubisco deactivates at moderately high temperature. Relationships between effects of moderate heat on rubisco activation and thylakoid reactions are not yet clear. Reactive oxygen species such as H2O2 may also be important during moderate heat stress. Rubisco can make hydrogen peroxide as a result of oxygenase side reactions and H2O2 production by rubisco was recently shown to increase substantially with temperature. The ability to withstand moderately high temperature can be improved by altering thylakoid lipid composition or by supplying isoprene. In my opinion this indicates that thylakoid reactions are important during moderate heat stress. The deactivation of rubisco at moderately high temperature could be a parallel deleterious effect or a regulatory response to limit damage to thylakoid reactions. 相似文献
17.
Primary Structure of Chlamydomonas reinhardtii Ribulose 1,5-Bisphosphate Carboxylase/Oxygenase Activase and Evidence for a Single Polypeptide 总被引:1,自引:0,他引:1
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Immunoblot analysis of ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco) activase from the green alga Chlamydomonas reinhardtii indicated the presence of a single polypeptide. This observation contrasts with the Spinacea oleracea (spinach) and Arabidopsis thaliana proteins, in which two polypeptide species are generated by alternative pre-mRNA splicing. A Chlamydomonas rubisco activase cDNA clone containing the entire coding region was isolated and sequenced. The open reading frame encoded a 408 amino acid, 45 kilodalton polypeptide that included a chloroplast transit peptide. The presumptive mature polypeptide possessed 62% and 65% amino acid sequence identity, respectively, with the spinach and Arabidopsis mature polypeptides. The Chlamydomonas rubisco activase transit peptide possessed almost no amino acid sequence identity with the higher plant transit peptides. The nucleotide sequence of Chlamydomonas rubisco activase cDNA provided no evidence for alternative mRNA splicing, consistent with the immunoblot evidence for only one polypeptide. Genomic DNA blot analysis indicated the presence of a single Chlamydomonas rubisco activase gene. In the presence of spinach rubisco activase, a lower extent and rate of activation were obtained in vitro with Chlamydomonas rubisco than with spinach rubisco. We conclude Chlamydomonas rubisco activase comprises a single polypeptide which differs considerably from the higher plant polypeptides with respect to primary structure. 相似文献
18.
Stefanie Tietz Sujith Puthiyaveetil Heather M. Enlow Robert Yarbrough Magnus Wood Dmitry A. Semchonok Troy Lowry Zhirong Li Peter Jahns Egbert J. Boekema Steven Lenhert Krishna K. Niyogi Helmut Kirchhoff 《The Journal of biological chemistry》2015,290(22):14091-14106
The structural organization of proteins in biological membranes can affect their function. Photosynthetic thylakoid membranes in chloroplasts have the remarkable ability to change their supramolecular organization between disordered and semicrystalline states. Although the change to the semicrystalline state is known to be triggered by abiotic factors, the functional significance of this protein organization has not yet been understood. Taking advantage of an Arabidopsis thaliana fatty acid desaturase mutant (fad5) that constitutively forms semicrystalline arrays, we systematically test the functional implications of protein crystals in photosynthetic membranes. Here, we show that the change into an ordered state facilitates molecular diffusion of photosynthetic components in crowded thylakoid membranes. The increased mobility of small lipophilic molecules like plastoquinone and xanthophylls has implications for diffusion-dependent electron transport and photoprotective energy-dependent quenching. The mobility of the large photosystem II supercomplexes, however, is impaired, leading to retarded repair of damaged proteins. Our results demonstrate that supramolecular changes into more ordered states have differing impacts on photosynthesis that favor either diffusion-dependent electron transport and photoprotection or protein repair processes, thus fine-tuning the photosynthetic energy conversion. 相似文献
19.
Three seedling lethal mutants of Zea mays with impaired photosynthesis are described. These recessive mutants were selected on the basis of high chlorophyll fluorescence. They have normal chlorophyll pigmentation but are unable to fix CO2 fully. Evidence is presented from fluorescence characteristics of isolated chloroplasts that both photosystem I and II mutants were isolated. Using conventional measures of photosynthetic electron transport, we suggest that the photosystem I mutant has limited ability to reduce NADP. The other two mutants are clearly blocked in photosystem II, one possibly lacking the primary electron acceptor. 相似文献
20.
Myxothiazol and antimycin A are shown to suppress the oxygen transient previously attributed to the flash-induced inhibition of chlororespiration in Chlamydomonas reinhardtii (Peltier et al. 1987, Biochim Biophys Acta 893: 83–90). However, these two compounds do not affect the photosynthetic electron transport chain as inferred by the insensitivity of the CO2-dependent photosynthetic O2 evolution and of the flash-induced electrochromic effect. Chlorophyll fluorescence induction measurements carried out in dark-adapted cells of a mutant of Chlamydomonas lacking photosystem 1, show that myxothiazol and antimycin A significantly increase the redox state of the photosystem 2 acceptors. We conclude from these results that chlororespiration is inhibited by myxothiazol and antimycin A and that the site of inhibition is located on the dark oxidation pathway of the plastoquinone pool. This inhibition is interpreted through the involvement of a myxothiazol and antimycin A sensitive cytochrome in the chlororespiratory chain.Abbreviations cyt
cytochrome
- PQ
plastoquinone
- PS
photosystem 相似文献