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Biological Research May 2017Acaryochloris marina is an oxygenic cyanobacterium that utilizes far-red light for photosynthesis. It has an expanded genome, which helps in its adaptability to the... (Review)
Review
Acaryochloris marina is an oxygenic cyanobacterium that utilizes far-red light for photosynthesis. It has an expanded genome, which helps in its adaptability to the environment, where it can survive on low energy photons. Its major light absorbing pigment is chlorophyll d and it has α-carotene as a major carotenoid. Light harvesting antenna includes the external phycobilin binding proteins, which are hexameric rods made of phycocyanin and allophycocyanins, while the small integral membrane bound chlorophyll binding proteins are also present. There is specific chlorophyll a molecule in both the reaction center of Photosystem I (PSI) and PSII, but majority of the reaction center consists of chlorophyll d. The composition of the PSII reaction center is debatable especially the role and position of chlorophyll a in it. Here we discuss the photosystems of this bacterium and its related biology.
Topics: Adaptation, Physiological; Chlorophyll; Cyanobacteria; Genome, Bacterial; Photosynthesis
PubMed: 28526061
DOI: 10.1186/s40659-017-0120-0 -
Biochimica Et Biophysica Acta Mar 2010Cyanobacteria adapt to varying light conditions by controlling the amount of excitation energy to the photosystems. On the minute time scale this leads to redirection of...
Cyanobacteria adapt to varying light conditions by controlling the amount of excitation energy to the photosystems. On the minute time scale this leads to redirection of the excitation energy, usually referred to as state transitions, which involves movement of the phycobilisomes. We have studied short-term light adaptation in isolated heterocysts and intact filaments from the cyanobacterium Nostoc punctiforme ATCC 29133. In N. punctiforme vegetative cells differentiate into heterocysts where nitrogen fixation takes place. Photosystem II is inactivated in the heterocysts, and the abundancy of Photosystem I is increased relative to the vegetative cells. To study light-induced changes in energy transfer to Photosystem I, pre-illumination was made to dark adapted isolated heterocysts. Illumination wavelengths were chosen to excite Photosystem I (708nm) or phycobilisomes (560nm) specifically. In heterocysts that were pre-illuminated at 708nm, fluorescence from the phycobilisome terminal emitter was observed in the 77K emission spectrum. However, illumination with 560nm light caused quenching of the emission from the terminal emitter, with a simultaneous increase in the emission at 750nm, indicating that the 560nm pre-illumination caused trimerization of Photosystem I. Excitation spectra showed that 560nm pre-illumination led to an increase in excitation transfer from the phycobilisomes to trimeric Photosystem I. Illumination at 708nm did not lead to increased energy transfer from the phycobilisome to Photosystem I compared to dark adapted samples. The measurements were repeated using intact filaments containing vegetative cells, and found to give very similar results as the heterocysts. This demonstrates that molecular events leading to increased excitation energy transfer to Photosystem I, including trimerization, are independent of Photosystem II activity.
Topics: Energy Transfer; Light; Nitrogen Fixation; Nostoc; Photosystem I Protein Complex; Photosystem II Protein Complex; Phycobilisomes; Thylakoids
PubMed: 20036211
DOI: 10.1016/j.bbabio.2009.12.014 -
The Plant Cell Aug 2008State transitions, or the redistribution of light-harvesting complex II (LHCII) proteins between photosystem I (PSI) and photosystem II (PSII), balance the...
State transitions, or the redistribution of light-harvesting complex II (LHCII) proteins between photosystem I (PSI) and photosystem II (PSII), balance the light-harvesting capacity of the two photosystems to optimize the efficiency of photosynthesis. Studies on the migration of LHCII proteins have focused primarily on their reassociation with PSI, but the molecular details on their dissociation from PSII have not been clear. Here, we compare the polypeptide composition, supramolecular organization, and phosphorylation of PSII complexes under PSI- and PSII-favoring conditions (State 1 and State 2, respectively). Three PSII fractions, a PSII core complex, a PSII supercomplex, and a multimer of PSII supercomplex or PSII megacomplex, were obtained from a transformant of the green alga Chlamydomonas reinhardtii carrying a His-tagged CP47. Gel filtration and single particles on electron micrographs showed that the megacomplex was predominant in State 1, whereas the core complex was predominant in State 2, indicating that LHCIIs are dissociated from PSII upon state transition. Moreover, in State 2, strongly phosphorylated LHCII type I was found in the supercomplex but not in the megacomplex. Phosphorylated minor LHCIIs (CP26 and CP29) were found only in the unbound form. The PSII subunits were most phosphorylated in the core complex. Based on these observations, we propose a model for PSII remodeling during state transitions, which involves division of the megacomplex into supercomplexes, triggered by phosphorylation of LHCII type I, followed by LHCII undocking from the supercomplex, triggered by phosphorylation of minor LHCIIs and PSII core subunits.
Topics: Animals; Chlamydomonas reinhardtii; Light-Harvesting Protein Complexes; Microscopy, Electron, Transmission; Phosphorylation; Photosystem II Protein Complex
PubMed: 18757554
DOI: 10.1105/tpc.108.059352 -
Plant & Cell Physiology Aug 2014Two photosystems, PSI and PSII, drive electron transfer in series for oxygenic photosynthesis using light energy. To balance the activity of the two photosystems under...
Two photosystems, PSI and PSII, drive electron transfer in series for oxygenic photosynthesis using light energy. To balance the activity of the two photosystems under varying light conditions, mobile antenna complexes, light-harvesting complex IIs (LHCIIs), shuttle between the two photosystems during state transitions. PSI forms a complex consisting of PSI core and its peripheral light-harvesting complex (LHCI) in plants and algae. In a previous study, we isolated a PSI-LHCI-LHCII supercomplex containing both LHCI and LHCII from state 2 cells of Chlamydomonas reinhardtii. In the present study, we isolated a PSI-LHCI-LHCII supercomplex associating with more LHCII complexes under a further optimized protocol. We determined its antenna size by three independent methods and revealed that the associated LHCIIs increased the antenna size by about 70 Chls and transferred light energy to the PSI core. Uniform labeling of total cellular proteins with (14)C indicated that the PSI-LHCI-LHCII supercomplex contains 1.85 copies of LhcbM5 and CP29 and 1.29 copies of CP26. PSI-LHCI-LHCII also stably bound 0.4 copy of ferredoxin-NADP(+) oxidoreductase (FNR) that catalyzes light-induced electron transfer from PSI to NADP(+) in the presence of ferredoxin. We discuss the possible organization of these LHCIIs in the PSI-LHCI-LHCII supercomplex.
Topics: Chlamydomonas reinhardtii; Chlorophyll; Electron Transport; Ferredoxin-NADP Reductase; Light; Light-Harvesting Protein Complexes; Models, Biological; Multiprotein Complexes; Oxidation-Reduction; Phosphorylation; Photosynthesis; Photosystem I Protein Complex; Photosystem II Protein Complex; Spectrometry, Fluorescence; Thylakoids
PubMed: 24867888
DOI: 10.1093/pcp/pcu071 -
Frontiers in Plant Science 2017The thylakoid membrane is the site of photochemical and electron transport reactions of oxygenic photosynthesis. The lipid composition of the thylakoid membrane, with...
The thylakoid membrane is the site of photochemical and electron transport reactions of oxygenic photosynthesis. The lipid composition of the thylakoid membrane, with two galactolipids, one sulfolipid, and one phospholipid, is highly conserved among oxygenic photosynthetic organisms. Besides providing a lipid bilayer matrix, thylakoid lipids are integrated in photosynthetic complexes particularly in photosystems I and II and play important roles in electron transport processes. Thylakoid lipids are differentially allocated to photosynthetic complexes and the lipid bilayer fraction, but distribution of each lipid in the thylakoid membrane is unclear. In this study, based on published crystallographic and biochemical data, we estimated the proportions of photosynthetic complex-associated and bilayer-associated lipids in thylakoid membranes of cyanobacteria and plants. The data suggest that ∼30 mol% of phosphatidylglycerol (PG), the only major phospholipid in thylakoid membranes, is allocated to photosystem complexes, whereas glycolipids are mostly distributed to the lipid bilayer fraction and constitute the membrane lipid matrix. Because PG is essential for the structure and function of both photosystems, PG buried in these complexes might have been selectively conserved among oxygenic phototrophs. The specific and substantial allocation of PG to the deep sites of photosystems may need a unique mechanism to incorporate PG into the complexes possibly in coordination with the synthesis of photosynthetic proteins and pigments.
PubMed: 29209350
DOI: 10.3389/fpls.2017.01991 -
The New Phytologist Oct 2023Drought is a major abiotic stress that impairs plant growth and development. Despite this, a comprehensive understanding of drought effects on the photosynthetic...
Drought is a major abiotic stress that impairs plant growth and development. Despite this, a comprehensive understanding of drought effects on the photosynthetic apparatus is lacking. In this work, we studied the consequences of 14-d drought treatment on Arabidopsis thaliana. We used biochemical and spectroscopic methods to examine photosynthetic membrane composition and functionality. Drought led to the disassembly of PSII supercomplexes and the degradation of PSII core. The light-harvesting complexes (LHCII) instead remain in the membrane but cannot act as an antenna for active PSII, thus representing a potential source of photodamage. This effect can also be observed during nonphotochemical quenching (NPQ) induction when even short pulses of saturating light can lead to photoinhibition. At a later stage, under severe drought stress, the PSI antenna size is also reduced and the PSI-LHCI supercomplexes disassemble. Surprisingly, although we did not observe changes in the PSI core protein content, the functionality of PSI is severely affected, suggesting the accumulation of nonfunctional PSI complexes. We conclude that drought affects both photosystems, although at a different stage, and that the operative quantum efficiency of PSII (Φ ) is very sensitive to drought and can thus be used as a parameter for early detection of drought stress.
Topics: Arabidopsis; Photosystem I Protein Complex; Droughts; Photosystem II Protein Complex; Photosynthesis; Light-Harvesting Protein Complexes; Chlorophyll
PubMed: 37530066
DOI: 10.1111/nph.19171 -
Journal of Photochemistry and... Jul 2009In this study, we investigated the energy dissipation processes via photosystem II and photosystem I activity in green alga Chlamydomonas reinhardtii exposed to...
In this study, we investigated the energy dissipation processes via photosystem II and photosystem I activity in green alga Chlamydomonas reinhardtii exposed to dichromate inhibitory effect. Quantum yield of photosystem II and also photosystem I were highly decreased by dichromate effect. Such inhibition by dichromate induced strong quenching effect on rapid OJIP fluorescence transients, indicating deterioration of photosystem II electron transport via plastoquinone pool toward photosystem I. The decrease of energy dissipation dependent on electron transport of photosystem II and photosystem I by dichromate effect was associated with strong increase of non-photochemical energy dissipation processes. By showing strong effect of dichromate on acceptor side of photosystem I, we indicated that dichromate inhibitory effect was not associated only with PSII electron transport. Here, we found that energy dissipation via photosystem I was limited by its electron acceptor side. By the analysis of P700 oxido-reduction state with methylviolagen as an exogenous PSI electron transport mediator, we showed that PSI electron transport discrepancy induced by dichromate effect was also caused by inhibitory effect located beyond photosystem I. Therefore, these results demonstrated that dichromate has different sites of inhibition which are associated with photosystem II, photosystem I and electron transport sink beyond photosystems.
Topics: Animals; Chlamydomonas reinhardtii; Chlorophyll; Electron Transport; Energy Metabolism; Fluorescent Dyes; Photosystem I Protein Complex; Photosystem II Protein Complex; Potassium Dichromate; Water Pollutants, Chemical
PubMed: 19427227
DOI: 10.1016/j.jphotobiol.2009.03.011 -
Biochimica Et Biophysica Acta Dec 1975The parameters listed in the title were determined within the context of a model for the photochemical apparatus of photosynthesis. The fluorescence of variable yield at...
The parameters listed in the title were determined within the context of a model for the photochemical apparatus of photosynthesis. The fluorescence of variable yield at 750 nm at -196 degrees C is due to energy transfer from Photosystem II to Photosystem I. Fluorescence excitation spectra were measured at -196 degrees C at the minimum, FO, level and the maximum, FM, level of the emission at 750 nm. The difference spectrum, FM-FO, which represents the excitation spectrum for FV is presented as a pure Photosystem II excitation spectrum. This spectrum shows a maximum at 677 nm, attributable to the antenna chlorophyll a of Photosystem II units, with a shoulder at 670 nm and a smaller maximum at 650 nm, presumably due to chlorophyll a and chlorophyll b of the light-harvesting chlorophyll complex. Fluoresence at the FO level at 750 nm can be considered in two parts; one part due to the fraction of absorbed quanta, alpha, which excites Photosystem I more-or-less directly and another part due to energy transfer from Photosystem II to Photosystem I. The latter contribution can be estimated from the ratio of FO/FV measured at 692 nm and the extent of FV at 750 nm. According to this procedure the excitation spectrum of Photosystem I at -196 degrees C was determined by subtracting 1/3 of the excitation spectrum of FV at 750 nm from the excitation spectrum of FO at 750 nm. The spectrum shows a relatively sharp maximum at 681 nm due to the antenna chlorophyll a of Photosystem I units with probably some energy transfer from the light-harvesting chlorophyll complex. The wavelength dependence of alpha was determined from fluorescence measurements at 692 and 750 nm at -196 degrees C. Alpha is constant to within a few percent from 400 to 680 nm, the maximum deviation being at 515 nm where alpha shows a broad maximum increasing from 0.30 to 0.34. At wavelengths between 680 and 700 nm, alpha increases to unity as Photosystem I becomes the dominant absorber in the photochemical apparatus.
Topics: Chloroplasts; Electron Transport; Freezing; Mathematics; Photophosphorylation; Photosynthesis; Plants; Quantum Theory; Spectrometry, Fluorescence
PubMed: 1191662
DOI: 10.1016/0005-2728(75)90131-0 -
Annual Review of Plant Biology 2006Oxygenic photosynthesis, the principal converter of sunlight into chemical energy on earth, is catalyzed by four multi-subunit membrane-protein complexes: photosystem I... (Review)
Review
Oxygenic photosynthesis, the principal converter of sunlight into chemical energy on earth, is catalyzed by four multi-subunit membrane-protein complexes: photosystem I (PSI), photosystem II (PSII), the cytochrome b(6)f complex, and F-ATPase. PSI generates the most negative redox potential in nature and largely determines the global amount of enthalpy in living systems. PSII generates an oxidant whose redox potential is high enough to enable it to oxidize H(2)O, a substrate so abundant that it assures a practically unlimited electron source for life on earth. During the last century, the sophisticated techniques of spectroscopy, molecular genetics, and biochemistry were used to reveal the structure and function of the two photosystems. The new structures of PSI and PSII from cyanobacteria, algae, and plants has shed light not only on the architecture and mechanism of action of these intricate membrane complexes, but also on the evolutionary forces that shaped oxygenic photosynthesis.
Topics: Photosystem I Protein Complex; Photosystem II Protein Complex; Protein Conformation
PubMed: 16669773
DOI: 10.1146/annurev.arplant.57.032905.105350 -
Plant Science : An International... Jun 2014Thermoluminescence emission from wheat leaves was recorded under various controlled drought stress conditions: (i) fast dehydration (few hours) of excised leaves in the...
Assessment of photosystem II thermoluminescence as a tool to investigate the effects of dehydration and rehydration on the cyclic/chlororespiratory electron pathways in wheat and barley leaves.
Thermoluminescence emission from wheat leaves was recorded under various controlled drought stress conditions: (i) fast dehydration (few hours) of excised leaves in the dark (ii) slow dehydration (several days) obtained by withholding watering of plants under a day/night cycle (iii) overnight rehydration of the slowly dehydrated plants at a stage of severe dessication. In fast dehydrated leaves, the AG band intensity was unchanged but its position was shifted to lower temperatures, indicating an activation of cyclic and chlororespiratory pathways in darkness, without any increase of their overall electron transfer capacity. By contrast, after a slow dehydration the AG intensity was strongly increased whereas its position was almost unchanged, indicating respectively that the capacity of cyclic pathways was enhanced but that they remained inactivated in darkness. Under more severe dehydration, the AG band almost disappeared. Rewatering caused its rapid bounce significantly above the control level. No significant differences in AG emission could be found between the two drought-sensitive and drought-tolerant wheat cultivars. The afterglow thermoluminescence emission in leaves provides an additional tool to follow the increased capacity and activation of cyclic electron flow around PSI in leaves during mild, severe dehydration and after rehydration.
Topics: Cell Respiration; Dehydration; Electron Transport; Hordeum; Luminescence; Photosystem II Protein Complex; Plant Leaves; Temperature; Triticum
PubMed: 24767121
DOI: 10.1016/j.plantsci.2014.03.013