Plastoquinone redox control of chloroplast thylakoid protein phosphorylation and distribution of excitation energy between photosystems: discovery, background, implications (original) (raw)
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Photosynthesis research, 2001
A cytochrome b (6) f deficient mutant of Lemna perpusilla maintains a constant and lower level of the light-harvesting chl a/b-binding protein complex II (LHC II) as compared to the wild type plants at low-light intensities. Inhibition of the plastoquinone pool reduction increases the LHC II content of the mutant at both low- and high-light intensities but only at high-light intensity in the wild type plants. Proteolytic activity against LHC II appears during high-light photoacclimation of wild type plants. However, the acclimative protease is present in the mutant at both light intensities. These and additional results suggest that the plastoquinone redox state serves as the major signal-transducing component in the photoacclimation process affecting both, synthesis and degradation of LHC II and appearance of acclimative LHC II proteolysis. The plastoquinol pool cannot be oxidized by linear electron flow in the mutant plants which are locked in a 'high light' acclimation st...
Photoactivation of the Electron Flow from NADPH to Plastoquinone in Spinach Chloroplasts
Plant and Cell Physiology, 1995
Intact chloroplasts from spinach showed a transient increase in Chi fluorescence after saturating illumination with actinic light and its yield depended on the duration of illumination and the intensity of the actinic light (AL). The increase was partially suppressed when antimycin A was added immediately after termination of the AL. The inhibited fluorescence increase, therefore, reflected the electron flow from the reductant(s) that had accumulated during the actinic illumination to the plastoquinone (PQ) pool via ferredoxin and the antimycin A-sensitive Cyt 6-559 [Miyake et al. (1995) Plant Cell Physiol. 36: 743]. Addition of dihydroxyacetone phosphate (DHAP) to chloroplasts caused the enhancement of the increase in fluorescence after AL, which was inhibited by antimycin A. Decay of the transiently raised fluorescence was retarded by 2-heptyl-4-hydroxyquinoline TV-oxide and stigmatellin, suggesting that re-oxidation of the reduced PQ pool is coupled with the operation of Q-cycle. Although the activity of the stromal enzyme system that supplies NADPH on addition of DHAP was constant irrespective of light or darkness, the capacity of the intact chloroplasts to show a DHAP-dependent fluorescence increase had a limited lifetime after AL was turned off. This result suggests that the antimycin A-sensitive Cyt 6-559 or ferredoxin-NADP reductase is activated by light and deactivated in the dark. In ruptured chloroplasts, the addition of NADPH increased the dark fluorescence yield only in the presence of Fd, which also was inhibited by antimycin A. Thus the photoregulatory mechanism of Cyt 6-559 (Fd) in intact chloroplasts appeared to be lost when chloroplasts were ruptured.
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1994
Regulation of thylakoid protein phosphorylation from saturating up to photoinhibitory light conditions was studied in intact chloroplasts with high rates of CO2 fixation and functioning protein biosynthesis. Comparing steady-state level phosphorylation with the phosphorylation in the presence of the phosphatase inhibitor NaF, evidence was found that phosphorylation of light harvesting chlorophyll-protein complex II (LHC II) and Photosystem II (PS II) polypeptides was catalysed by at least two different kinase/phosphatase systems. Whereas the steady-state level of LHC II phosphorylation declined with increasing light intensity, the phosphorylation level of PS II polypeptides remained stable even at photoinhibitory conditions. Decrease of steady-state level of LHC II phosphorylation at higher light intensities was partially due to an inhibition of the phosphorylation reaction. Its inactivation was observed before any significant loss of PS II electron transfer activity occurred. Quenching analysis of chlorophyll fluorescence revealed that the high light inhibition of the LHC II phosphorylation reaction was caused by an increased membrane energetisation, and not by an oxidation of the plastoquinone pool. In contrast, the kinase activity responsible for the phosphorylation of the PS II polypeptides seemed to be exclusively under the redox control of the plastoquinone pool and was not influenced by membrane energetisation. Evidence was found that also the phosphatase activities specific for LHC II and PS II proteins were different. As indicated by the high turnover of phosphate groups bound to LHC II, the LHC II specific phosphatase showed a high activity. Its activity was stimulated at higher light intensities and determined to a main extent the steady state level of LHC II phosphorylation. The phosphatase specific for the PS II phosphoproteins showed almost no activity in the light as indicated by the absence of a phosphate group turnover in the light. Dephosphorylation of PS II could only be observed in the dark and in contrast to LHC II dephosphorylation could not be inhibited by NaF. Even the increased turnover of the D1 protein at higher light intensities, which was followed by the light-dependent incorporation of [14C]leucine into the protein, did not accelerate the D1 protein phosphorylation. The steady-state level of PS II protein phosphorylation was therefore in principle determined by its kinase activity.
Biochimica et biophysica acta, 2014
Non-photochemical (dark) increases in chlorophyll a fluorescence yield associated with non-photochemical reduction of redox carriers (Fnpr) have been attributed to the reduction of plastoquinone (PQ) related to cyclic electron flow (CEF) around photosystem I. In vivo, this rise in fluorescence is associated with activity of the chloroplast plastoquinone reductase (plastid plastoquinone oxidoreductase) complex. In contrast, this signal measured in isolated thylakoids has been attributed to the activity of the protein gradient regulation-5 (PGR5)/PGR5-like (PGRL1)-associated CEF pathway. Here, we report a systematic experimentation on the origin of Fnpr in isolated thylakoids. Addition of NADPH and ferredoxin to isolated spinach thylakoids resulted in the reduction of the PQ pool, but neither its kinetics nor its inhibitor sensitivities matched those of Fnpr. Notably, Fnpr was more rapid than PQ reduction, and completely insensitive to inhibitors of the PSII QB site and oxygen evolvin...
Reduction of the plastoquinone pool by exogenous NADH and NADPH in higher plant chloroplasts
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1998
Chlorophyll fluorescence measurements were performed on osmotically lysed potato chloroplasts in order to characterize the reactions involved in the dark reduction of photosynthetic inter-system chain electron carriers. Addition of NADH or NADPH to lysed chloroplasts increased the chlorophyll fluorescence level measured in the presence of a non-actinic light Ž . until reaching F , thus indicating an increase in the redox state of the plastoquinone PQ pool. The fluorescence increase max was more pronounced when the experiment was carried out under anaerobic conditions and was about 50% higher when Ž . NADH rather than NADPH was used as an electron donor. The NAD P H-PQ oxidoreductase reaction was inhibited by diphenylene iodonium, N-ethylmaleimide and dicoumarol, but insensitive to rotenone, antimycin A and piericidin A. By comparing the substrate specificity and the inhibitor sensitivity of this reaction to the properties of spinach ferredoxinq Ž . Ž . NADP -reductase FNR , we infer that FNR is not involved in the NAD P H-PQ oxidoreductase activity and conclude to Ž . the participation of rotenone-insensitive NAD P H-PQ oxidoreductase. By measuring light-dependent oxygen uptake in the presence of DCMU, methyl viologen and NADH or NADPH as an electron donors, the electron flow rate through the Ž .
Biochemistry, 2002
Phosphatidylglycerol (PG), a ubiquitous constituent of thylakoid membranes of chloroplasts and cyanobacteria, is demonstrated to be essential for the functionality of plastoquinone electron acceptor Q B in the photosystem II reaction center of oxygenic photosynthesis. Growth of the pgsA mutant cells of Synechocystis sp. PCC6803 that are defective in phosphatidylglycerolphosphate synthase and are incapable of synthesizing PG, in a medium without PG, resulted in a 90% decrease in PG content and a 50% loss of photosynthetic oxygen-evolving activity as reported [Hagio, M., Gombos, Z., Várkonyi, Z., Masamoto, K., Sato, N., Tsuzuki, M., and Wada, H. (2000) Plant Physiol. 124, 795-804]. We have studied each step of the electron transport in photosystem II of the pgsA mutant to clarify the functional site of PG. Accumulation of Q Awas indicated by the fast rise of chlorophyll fluorescence yield under continuous and flash illumination. Oxidation of Q Aby Q B plastoquinone was shown to become slow, and Q Areoxidation required a few seconds when measured by double flash fluorescence measurements. Thermoluminescence measurements further indicated the accumulation of the S 2 Q Astate but not of the S 2 Q Bstate following the PG deprivation. These results suggest that the function of Q B plastoquinone was inactivated by the PG deprivation. We assume that PG is an indispensable component of the photosystem II reaction center complex to maintain the structural integrity of the Q B -binding site. These findings provide the first clear identification of a specific functional site of PG in the photosynthetic reaction center.
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1983
The quenching of Photosystem II (PS 11) chlorophyll fluorescence by oxidised plastoquinone has been used in an attempt to determine their relative distribution in the partition zone and stroma-exposed thylakoid membranes. Thus, the PS II-plastoquinone interaction was determined in stacked (2.5 mM MgC! 2) and largely unstacked (0.25 mM MgCI2) membranes. A method to correct for spiliover or other quenching changes at the different MgC! 2 concentrations, which would compete with the plastoquinone-induced quenching, was devised utilising the quinone dibromothymoquinone. This compound is demonstrated to behave as an ideal (theoretically) PS II quencher at both high and low MgCi 2 concentrations, which indicates that it distributes itself homogeneously between partition zone and stroma-exposed membrane regions. In passing from the stacked to the unstacked configuration, the PS lI-plastoquinone interaction decreases less than the PS ll-dibromothymoquinone interaction. This is interpreted to mean that plastoquinone is present in both the partition zone and stroma-exposed membranes, with somewhat higher concentrations in the stroma-exposed membranes. Thus, plastoquinone is well placed to transport reducing equivalents from the partition zones to the stroma-exposed membranes.