Excitation pressure regulates the activation energy for recombination events in the photosystem II reaction centres of Chlamydomonas reinhardtii

2007 ◽  
Vol 85 (6) ◽  
pp. 721-729 ◽  
Author(s):  
Tessa Pocock ◽  
P. V. Sane ◽  
S. Falk ◽  
N. P.A. Hüner
Keyword(s):  
Activation Energy ◽  
Photosystem Ii ◽  
Redox Potential ◽  
Chlamydomonas Reinhardtii ◽  
Reaction Center ◽  
Growth Conditions ◽  
High Irradiance ◽  
Reaction Centres ◽  
Excitation Pressure

Using in vivo thermoluminescence, we examined the effects of growth irradiance and growth temperature on charge recombination events in photosystem II reaction centres of the model green alga Chlamydomonas reinhardtii. We report that growth at increasing irradiance at either 29 or 15 °C resulted in comparable downward shifts in the temperature peak maxima (TM) for S2QB– charge pair recombination events, with minimal changes in S2QA– recombination events. This indicates that such growth conditions decrease the activation energy required for S2QB– charge pair recombination events with no concomitant change in the activation energy for S2QA– recombination events. This resulted in a decrease in the ΔTM between S2QA– and S2QB– recombination events, which was reversible when shifting cells from low to high irradiance and back to low irradiance at 29 °C. We interpret these results to indicate that the redox potential of QB was modulated independently of QA, which consequently narrowed the redox potential gap between QA and QB in photosystem II reaction centres. Since a decrease in the ΔTM between S2QA– and S2QB– recombination events correlated with growth at increasing excitation pressure, we conclude that acclimation to growth under high excitation pressure narrows the redox potential gap between QA and QB in photosystem II reaction centres, enhancing the probability for reaction center quenching in C. reinhardtii. We discuss the molecular basis for the modulation of the redox state of QB, and suggest that the potential for reaction center quenching complements antenna quenching via the xanthophyll cycle in the photoprotection of C. reinhardtii from excess light.

Psb30 is a photosystem II reaction center subunit and is required for optimal growth in high light in Chlamydomonas reinhardtii

2011 ◽  
Vol 104 (1-2) ◽  
pp. 220-228 ◽  
Author(s):  
Natsuko Inoue-Kashino ◽  
Yasuhiro Kashino ◽  
Yuichiro Takahashi
Keyword(s):  
Photosystem Ii ◽  
Chlamydomonas Reinhardtii ◽  
Reaction Center ◽  
Optimal Growth ◽  
High Light

scholarly journals Replacement of α-Tocopherol by β-Tocopherol Enhances Resistance to Photooxidative Stress in a Xanthophyll-Deficient Strain of Chlamydomonas reinhardtii

2009 ◽  
Vol 8 (11) ◽  
pp. 1648-1657 ◽  
Author(s):  
Anchalee Sirikhachornkit ◽  
Jai W. Shin ◽  
Irene Baroli ◽  
Krishna K. Niyogi
Keyword(s):  
Vitamin E ◽  
Photosystem Ii ◽  
Chlamydomonas Reinhardtii ◽  
Antioxidant Activities ◽  
Lipid Peroxide ◽  
Experimental System ◽  
High Light ◽  
Photooxidative Stress ◽  
Triple Mutant

ABSTRACT Tocopherols (vitamin E) comprise a class of lipid-soluble antioxidants synthesized only in plants, algae, and some cyanobacteria. The majority of tocopherols in photosynthetic cells is in the α form, which has the highest vitamin E activity in humans, whereas the β, γ, and δ forms normally account for a small percentage of total tocopherols. The antioxidant activities of these forms of tocopherol differ depending on the experimental system, and their relative activities in vivo are unclear. In a screen for suppressors of the xanthophyll-deficient npq1 lor1 double mutant of Chlamydomonas reinhardtii, we isolated a vte3 mutant lacking α-tocopherol but instead accumulating β-tocopherol. The vte3 mutant contains a mutation in the homolog of a 2-methyl-6-phytyl-1,4-benzoquinone methyltransferase gene found in plants. The vte3 npq1 lor1 triple mutant with β-tocopherol survived better under photooxidative stress than did the npq1 lor1 mutant, but the vte3 mutant on its own did not have an obvious phenotype. Following transfer from low light to high light, the triple mutant showed a higher efficiency of photosystem II, a higher level of cell viability, and a lower level of lipid peroxide, a marker for oxidative stress, than did the npq1 lor1 mutant. After high-light transfer, the level of the photosystem II reaction center protein, D1, was also higher in the vte3 npq1 lor1 mutant, but the rate of D1 photodamage was not significantly different from that of the npq1 lor1 mutant. Taken together, these results suggest that the replacement of α-tocopherol by β-tocopherol in a xanthophyll-deficient strain of Chlamydomonas reinhardtii contributes to better survival under conditions of photooxidative stress.

scholarly journals Phosphorylation of chlamydomonas reinhardi chloroplast membrane proteins in vivo and in vitro.

1982 ◽  
Vol 93 (3) ◽  
pp. 712-718 ◽  
Author(s):  
G C Owens ◽  
I Ohad
Keyword(s):  
Membrane Proteins ◽  
Photosystem Ii ◽  
Binding Site ◽  
Reaction Center ◽  
Thylakoid Membrane ◽  
Red Light ◽  
Intact Cells ◽  
Turnover Process

Phosphorylation of thylakoid membrane proteins in the chloroplast of wild-type and mutant strains of Chlamydomonas reinhardi has been studied in vivo and in vitro. Intact cells or purified membranes were labeled with [32P]orthophosphate or [gamma-32P]ATP, respectively, and the presence of phosphorylated polypeptides was detected by autoradiography after membrane fractionation by SDS PAGE. The 32P was esterified to serine and threonine residues. At least six polypeptides were phosphorylated in vitro and in vivo, and corresponded to components of the photosystem II complex contributing to the formation of the light-harvesting-chlorophyll (LHC) a,b-protein complex, the DCMU binding site (32-35 kdaltons), and the reaction center (26 kdaltons). In agreement with previous reports (Alfonzo, et al., 1979, Plant Physiol., 65:730-734; and Bennett, 1979, FEBS (Fed. Eur. Biochem. Soc.) Lett., 103:342-344), the membrane-bound protein kinase was markedly stimulated by light in vitro via a mechanism requiring photosystem II activity. Phosphorylation of thylakoid membrane polypeptides in vivo was, however, completely independent of illumination. Similar amounts of phosphate were incorporated into the photosynthetic membranes of cells incubated in the dark, in white light with or without 3-(3,4-dichlorophenyl-1,1-dimethyl urea (DCMU), or in red or far-red light. Different turnovers of the phosphate were observed in the light and dark, and a phosphoprotein phosphatase involved in this turnover process was also associated with the membrane. Comparison of the amount of esterified phosphate per protein in vivo and the maximum incorporation in isolated membranes revealed that only a small fraction of the available sites could be phosphorylated in vitro. In contrast to the DCMU binding site, the LHC and 26-kdalton polypeptide were not phosphorylated in vivo when the reaction center II polypeptides of 44-54 kdaltons were missing. The finding that all the phosphoproteins appear to be components of the photosystem II complex and are only partially dephosphorylated in vivo suggests strongly that protein phosphorylation might play an important role in the maintenance of the organizational integrity of this complex. The observation that the LHC is not phosphorylated in the absence of the reaction center lends support to this idea.

scholarly journals Correlation between changes in light energy distribution and changes in thylakoid membrane polypeptide phosphorylation in Chlamydomonas reinhardtii.

1984 ◽  
Vol 98 (1) ◽  
pp. 1-7 ◽  
Author(s):  
F A Wollman ◽  
P Delepelaire
Keyword(s):  
Photosystem Ii ◽  
Chlamydomonas Reinhardtii ◽  
Redox State ◽  
Light Harvesting ◽  
Anaerobic Treatment ◽  
Intact Cells ◽  
Light Harvesting Complex ◽  
Plastoquinone Pool

We have used a new method to extensively modify the redox state of the plastoquinone pool in Chlamydomonas reinhardtii intact cells. This was achieved by an anaerobic treatment that inhibits the chlororespiratory pathway recently described by P. Bennoun (Proc. Natl. Acad. Sci. USA, 1982, 79:4352-4356). A state I (plus 3,4-dichlorophenyl-1,1-dimethylurea) leads to anaerobic state transition induced a decrease in the maximal fluorescence yield at room temperature and in the FPSII/FPSI ratio at 77 degrees K, which was three times larger than in a classical state I leads to state II transition. The fluorescence changes observed in vivo were similar in amplitude to those observed in vitro upon transfer to the light of dark-adapted, broken chloroplasts incubated in the presence of ATP. We then compared the phosphorylation pattern of thylakoid polypeptides in C. reinhardtii in vitro and in vivo using gamma-[32P]ATP and [32P]orthophosphate labeling, respectively. The same set of polypeptides, mainly light-harvesting complex polypeptides, was phosphorylated in both cases. We observed that this phosphorylation process is reversible and is mediated by the redox state of the plastoquinone pool in vivo as well as in vitro. Similar changes of even larger amplitude were observed with the F34 mutant intact cells lacking in photosystem II centers. The presence of the photosystem II centers is then not required for the occurrence of the plastoquinone-mediated phosphorylation of light-harvesting complex polypeptides.

Reduced levels of cytochrome b 6/f in transgenic tobacco increases the excitation pressure on Photosystem II without increasing sensitivity to photoinhibition in vivo

1996 ◽  
Vol 50 (2) ◽  
pp. 159-169 ◽  
Author(s):  
Vaughan Hurry ◽  
Jan M. Anderson ◽  
Murray R. Badger ◽  
G. Dean Price
Keyword(s):  
Photosystem Ii ◽  
Transgenic Tobacco ◽  
Cytochrome B ◽  
Excitation Pressure

Primary Electron Donor(s) in Isolated Reaction Center of Photosystem II from Chlamydomonas reinhardtii

2012 ◽  
Vol 116 (16) ◽  
pp. 4860-4870 ◽  
Author(s):  
Khem Acharya ◽  
Valter Zazubovich ◽  
Mike Reppert ◽  
Ryszard Jankowiak
Keyword(s):  
Photosystem Ii ◽  
Chlamydomonas Reinhardtii ◽  
Reaction Center ◽  
Electron Donor ◽  
Primary Electron ◽  
Primary Electron Donor

Photoinactivation of Photosystem II and Degradation of the D1 Protein are Reduced in a Cytochrome b6/f -Less Mutant of Chlamydomonas reinhardtii

1990 ◽  
Vol 45 (5) ◽  
pp. 395-401 ◽  
Author(s):  
Susana Shochat ◽  
Noam Adir ◽  
Alma Gal ◽  
Yorinao Inoue ◽  
Laurence Mets ◽  
...  
Keyword(s):  
Photosystem Ii ◽  
Chlamydomonas Reinhardtii ◽  
Reaction Center ◽  
Electron Flow ◽  
D1 Protein ◽  
Charge Recombination ◽  
Cyt B ◽  
Variable Fluorescence ◽  
Cytochrome B6 ◽  
Mutant Cells

Abstract The effect of unoccupancy of the QB site by plastoquinone on the photoinactivation of reaction center II in a Cyt b6/f-less mutant of Chlamydomonas reinhardtii, B6, was investigated. In these cells the oxidation of plastoquinol generated by electron flow via RC II to plastoquinone and thus the turnover of PQH2/PQ via the QB site are drastically reduced. Reaction center II of the mutant cells was resistant to photoinactivation relative to the control cells as demonstrated by measurements of light-induced destabilization of S2-QB charge recombination, rise in in­ trinsic fluorescence and loss of variable fluorescence. These parameters relate to functions in­ volving the reaction center II D1 protein. The light-induced degradation of D1 in the mutant cells was also considerably reduced, with a t 1/2 value of 7 h as compared, under similar conditions, to about 1.5 h for the control cells. These results indicate that the photoinactivation of RC II and turnover of the D1 protein are related and require occupancy of the QB site by PQ and its light-driven reduction.

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