Cyclic electron transport in isolated intact chloroplasts. Further studies with antimycin

Mills, John D.; Slovacek, R.E.; Hínd, Geoffrey

doi:10.1016/0005-2728(78)90178-0

Cited by 68 publications

(39 citation statements)

References 36 publications

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“…These low rates of 02 uptake were relatively insensitive to increases in light intensity which greatly stimulated photosynthesis (14). These and a number of other workers (3,4,20,23,32) have provided evidence for cyclic flow during photosynthesis in thylakoids, chloroplasts, and intact leaves. Quantitative measurements of Cyt turnover in intact chloroplasts (26) have also indicated substantial cyclic flow.…”

Section: Introductionmentioning

confidence: 60%

“…The effect of antimycin A on photosynthetic activities in thylakoids and intact chloroplasts is complex and apparently depends on the experimental conditions involved (7,14,19,20,22,23,25,28). Figure 1 shows that the photoreduction of methyl viologen in intact chloroplasts is insensitive to antimycin A up to 4 Am in the presence and absence of 10 mm NH4CL.…”

Section: Resultsmentioning

confidence: 99%

“…2, 3, and 5), but not NH4CI (Table I) chloroplast preparations in the presence of antimycin A. The simplest explanation for these observations is that antimycin A primarily inhibited cyclic electron flow and caused a decrease in the supply of ATP for photosynthesis (4,14,20,23). However, the reduction of N02 or oxaloacetate via linear electron flow would lead to 02 evolution and a net generation of ATP without the formation of NADPH and thus would restore the ATP/NADPH balance.…”

Section: Discussionmentioning

confidence: 97%

“…high Pi concentration) for CO2 fixation (28). But under aerobic conditions at optimal Pi, antimycin A strongly inhibited photosynthetic CO2 fixation in intact chloroplasts with concomitant decreases in energy-dependent processes such as Chl a fluorescence, 9-aminoacridine fluorescence quenching, light scattering changes at 535 nm, and the slow electrochromic absorbance changes at 518 nm (14,20,23). This evidence suggests that the inhibition of photosynthesis in intact chloroplasts by antimycin A is directly linked to the inhibition of cyclic electron flow.…”

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confidence: 96%

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Evidence for Cyclic Photophosphorylation during ¹⁴CO₂ Fixation in Intact Chloroplasts

Woo¹

1983

Plant Physiol.

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This study examines the effect of antimycin A and nitrite on 14CO2 fixation in intact chloroplasts isolated from spinach (Spiucia oeracea L.) leaves. Antimycin A (2 micromolar) strongly inhibited CO2 fixation but did not appear to inhibit or uncouple linear electron transport in intact chloroplasts. The addition of small quantities (40-100 micromolar) of nitrite A stoichiometric balance of ATP/NADPH in the chloroplast is essential for optimum photosynthesis. It is now widely accepted that such a stoichiometric balance of ATP/NADPH could not be achieved by linear electron transport from H20 to NADP+ alone (1 1). Assuming that the ATP/NADPH ratio generated via linear electron transport is 1.33, the extra ATP needed would presumably be derived from cyclic and/or pseudocyclic electron transport.High rates of 02 uptake have been measured in thylakoid preparations from spinach leaves in the presence of high concentrations of Fd (1; R. T. Furbank and M. R. Badger, unpublished), during photosynthesis in intact chloroplasts and cells (8,9), and in leaves of C3 plants (6,10). The values of 02 uptake measured in these studies are comparable to and, in several cases, exceeded the value (1 1.3% of total 02 evolution) required for the generation of all the extra ATP needed for CO2 fixation. This evidence suggests that pseudocyclic electron transport plays a significant (dominant) role in the ATP/NADPH balance during photosynthesis. Marsho et al. (18) found that, although there was a significant rate of 02 uptake in intact chloroplasts during the lag phase of photosynthesis, this diminished to a relatively insignificant level during steady-state photosynthesis. These low rates of 02 uptake were relatively insensitive to increases in light intensity which greatly stimulated photosynthesis (14). These and a number of other workers (3,4,20,23,32) have provided evidence for cyclic flow during photosynthesis in thylakoids, chloroplasts, and intact leaves. Quantitative measurements of Cyt turnover in intact chloroplasts (26) have also indicated substantial cyclic flow. But the corresponding rates of 02 evolution during these measurements were low. Thus, the relative contribution of cyclic versus pseudocyclic flow to the ATP/NADPH balance during photosynthesis remains unresolved. Furthermore, the reasons for the discrepancies between high (8, 9) and low (14, 18) rates of 02 uptake measured during photosynthesis in chloroplasts and cells remain to be resolved.In thylakoids, antimycin A is a reported potent inhibitor of Fddependent cyclic flow (2) but may function as an uncoupler at higher concentrations (7). In intact chloroplasts, antimycin A stimulated CO2 fixation under anaerobic conditions (19,22,25) and in aerobic conditions which were suboptimal (e.g. high Pi concentration) for CO2 fixation (28). But under aerobic conditions at optimal Pi, antimycin A strongly inhibited photosynthetic CO2 fixation in intact chloroplasts with concomitant decreases in energy-dependent processes such as Chl a fluorescence, 9-aminoacridin...

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Section: Introductionmentioning

confidence: 60%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 97%

mentioning

confidence: 96%

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Evidence for Cyclic Photophosphorylation during ¹⁴CO₂ Fixation in Intact Chloroplasts

Woo¹

1983

Plant Physiol.

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“…The inhibition of photosynthesis by antimycin A measured using in vitro systems such as thylakoids or chloroplasts generally reported in the literature is much more important, generally between 50% and 80% (Tagawa et al, 1963;Mills et al, 1978;Woo, 1983;Moss and Bendall, 1984;Cleland and Bendall, 1992). We observed a much more important inhibition of the photosynthetic electron transport activity in ndhB Ϫ plants (approximately 50%).…”

Section: Involvement Of the Ndh Complex In Cyclic Electron Flow Arounmentioning

confidence: 96%

Increased Sensitivity of Photosynthesis to Antimycin A Induced by Inactivation of the Chloroplast ndhB Gene. Evidence for a Participation of the NADH-Dehydrogenase Complex to Cyclic Electron Flow around Photosystem I

et al. 2001

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) were used to study the role of the NADH-dehydrogenase complex (NDH) during photosynthesis and particularly the involvement of this complex in cyclic electron flow around photosystem I (PSI). Photosynthetic activity was determined on leaf discs by measuring CO 2 exchange and chlorophyll fluorescence quenchings during a dark-to-light transition. In the absence of treatment, both non-photochemical and photochemical fluorescence quenchings were similar in ndhB Ϫ and wild type (WT). When leaf discs were treated with 5 m antimycin A, an inhibitor of cyclic electron flow around PSI, both quenchings were strongly affected. At steady state, maximum photosynthetic electron transport activity was inhibited by 20% in WT and by 50% in ndhB Ϫ . Under non-photorespiratory conditions (2% O 2 , 2,500 L L Ϫ1 CO 2 ), antimycin A had no effect on photosynthetic activity of WT, whereas a 30% inhibition was observed both on quantum yield of photosynthesis assayed by chlorophyll fluorescence and on CO 2 assimilation in ndhB Ϫ . The effect of antimycin A on ndhB Ϫ could not be mimicked by myxothiazol, an inhibitor of the mitochondrial cytochrome bc 1 complex, therefore showing that it is not related to an inhibition of the mitochondrial electron transport chain but rather to an inhibition of cyclic electron flow around PSI. We conclude to the existence of two different pathways of cyclic electron flow operating around PSI in higher plant chloroplasts. One of these pathways, sensitive to antimycin A, probably involves ferredoxin plastoquinone reductase, whereas the other involves the NDH complex. The absence of visible phenotype in ndhB Ϫ plants under normal conditions is explained by the complement of these two pathways in the supply of extra-ATP for photosynthesis.During oxygenic photosynthesis of C 3 plants, both photosystem II (PSII) and photosystem I (PSI) cooperate to achieve NADP ϩ reduction using water as an electron donor and generate a trans-membrane proton gradient driving ATP synthesis. Although NADP ϩ reduction is recognized to be dependent on the activity of both photosystems through electron transport reactions of the "Z" scheme (Hill and Bendall, 1960;Redding et al., 1999), it has early been reported from studies on isolated thylakoids that ATP could be produced by the sole PSI through cyclic electron transfer reactions (Arnon, 1959). The cyclic electron flow around PSI has been extensively studied in thylakoids and/or chloroplasts of C 3 plants (for review, see Fork and Herbert, 1993; Bendall and Manasse, 1995). This mechanism has been suggested to provide ATP for a variety of cellular processes, including stress adaptation (Havaux et al., 1991) and CO 2 fixation (Furbank and Horton, 1987; Herbert et al., 1990). During photosynthetic CO 2 fixation, both NADPH and ATP are used to regenerate ribulose-1,5-bisphosphate and allow functioning of the photosynthetic carbon reduction cycle (Calvin cycle). In the absence of Q cycle, when one NADPH is produced by linear electron transport reactions, four H ϩ are released in ...

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The Antimycin-binding Site of Thylakoid Membranes from Chloroplasts

Davies

Bendall

1987

Progress in Photosynthesis Research

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Cyclic electron transport in isolated intact chloroplasts. Further studies with antimycin

Cited by 68 publications

References 36 publications

Evidence for Cyclic Photophosphorylation during ¹⁴CO₂ Fixation in Intact Chloroplasts

Evidence for Cyclic Photophosphorylation during ¹⁴CO₂ Fixation in Intact Chloroplasts

Increased Sensitivity of Photosynthesis to Antimycin A Induced by Inactivation of the Chloroplast ndhB Gene. Evidence for a Participation of the NADH-Dehydrogenase Complex to Cyclic Electron Flow around Photosystem I

The Antimycin-binding Site of Thylakoid Membranes from Chloroplasts

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Cyclic electron transport in isolated intact chloroplasts. Further studies with antimycin

Cited by 68 publications

References 36 publications

Evidence for Cyclic Photophosphorylation during 14CO2 Fixation in Intact Chloroplasts

Evidence for Cyclic Photophosphorylation during 14CO2 Fixation in Intact Chloroplasts

Increased Sensitivity of Photosynthesis to Antimycin A Induced by Inactivation of the Chloroplast ndhB Gene. Evidence for a Participation of the NADH-Dehydrogenase Complex to Cyclic Electron Flow around Photosystem I

The Antimycin-binding Site of Thylakoid Membranes from Chloroplasts

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Evidence for Cyclic Photophosphorylation during ¹⁴CO₂ Fixation in Intact Chloroplasts

Evidence for Cyclic Photophosphorylation during ¹⁴CO₂ Fixation in Intact Chloroplasts