Photosystem I-abhängige Phosphorylierung isolierter Chloroplasten mit Ascorbat/2.6-Dichlorphenolindophenol als Elektronendonator und Methylviologen als Elektronenakzeptor / Photosystem I Dependent Phosphorylation of Isolated Chloroplasts with Ascorbate/2,6-Dichlorophenolindophenol as Electron Donor and Methylviologen as Electron Acceptor

1972 ◽  
Vol 27 (4) ◽  
pp. 445-455 ◽  
Author(s):  
Heinrich Strotmann ◽  
Christa Von Gösseln
Keyword(s):  
Electron Transport ◽  
Linear System ◽  
Photosystem I ◽  
Electron Acceptor ◽  
Electron Flow ◽  
Phosphorylation Site ◽  
Cyclic System ◽  
Atp Production ◽  
Proton Uptake ◽  
Isolated Chloroplasts

Photosystem I related phosphorylation of isolated chloroplasts was investigated with special reference to the stoichiometry between ATP production and electron transprt (ATP: 2e⊖). The system studied contained DCMU to inhibit electron flow from photosystem II, ascorbate and DPIP to supply electrons to photosystem I, and methylviologen as electron acceptor. The following results were obtained:1. Basal electron transport is stimulated by the addition of the phosphorylating system, indicating that phosphorylation is really coupled to non-cyclic electron flow. The ratio ATP: 2e⊖ is 1, when the increase of electron flow obtained by the addition of ADP and phosphate is correlated to phosphorylation. This ratio is constant upon varying several parameters including DPIP concentration and light intensity.2. In the absence of methylviologen a DPIP catalyzed cyclic phosphorylation takes place (cf. I. c.7, 11, 12). Phosphorylation is not increased by the addition of methylviologen, indicating that both, the cyclic DPIP mediated and the non-cyclic system are coupled to the same phosphorylation site and limited by the same reaction step.3. In the absence of oxygen a methylviologen supported cyclic phosphorylation occurs. Comparing optimum rates, phosphorylation under these conditions is about twice as high as in the noncyclic system. Therefore we conclude that two phosphorylation sites are involved in methylviologen catalyzed cyclic electron transport. This system is sensitive against trypsin treatment of the chloroplasts, whereas the linear system is not.4. The two cyclic systems as well as the non-cyclic system are coupled to reversible proton uptake. Furthermore the linear system exhibits an irreversible uptake of hydrogen ions, which is stoichiometric to electron flow. From the reversible and the irreversible components of the pH changes the ratio of the proton pump to electron transprt can be calculated. Under steady state conditions the ration H⨁ : e⊖ approaches 1.

The site of electron transport inhibition by bentazon (3-isopropyl-1H-2,1,3-benzothiadiazin-(4)3H-one 2,2-dioxide) in isolated chloroplasts

1982 ◽  
Vol 60 (4) ◽  
pp. 409-412 ◽  
Author(s):  
Rungsit Suwanketnikom ◽  
Kriton K. Hatzios ◽  
Donald Penner ◽  
Duncan Bell
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Photosystem I ◽  
Electron Acceptor ◽  
Photosynthetic Electron Transport ◽  
Primary Electron ◽  
Photochemical Reactions ◽  
Spinacea Oleracea ◽  
Primary Electron Acceptor ◽  
Isolated Chloroplasts

The effect of bentazon (3-isopropyl-1H-2,1,3-benzathiadiazin-(4)3H-one 2,2-dioxide) on various photochemical reactions of isolated spinach (Spinacea oleracea L.) chloroplasts was studied at concentrations 0, 5, 15, 45, and 135 μM. Bentazon at a concentration of 135 μM strongly inhibited uncoupled electron transport from water to ferricyanide or to methylviologen with inhibition percentages greater than 90%. Photosystem II mediated electron transport from water to oxidized diaminodurene, with 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) blocking photosystem I, was also strongly inhibited by bentazon at 135 μM but less with lower concentrations of bentazon. Photosystem I mediated transfer of electrons from diaminodurene to methylviologen, with 3,4-dichlorophenyl-1,1-dimethylurea (DCMU) blocking photosystem II, was not inhibited by bentazon at any concentration examined. Transfer of electrons from catechol to methylviologen in hydroxylamine-treated chloroplasts was inhibited by bentazon, and the inhibition percentages were again concentration dependent. The data indicate that the site of bentazon inhibition of the photosynthetic electron transport is at the reducing side of photosystem II, between the primary electron acceptor Q and plastoquinone.

Effects of Difenzoquat on Photoreactions and Respiration in Wheat (Triticum aestivum) and Wild Oat (Avena fatua)

Weed Science ◽  
1983 ◽  
Vol 31 (5) ◽  
pp. 693-699 ◽  
Author(s):  
Blaik P. Halling ◽  
Richard Behrens
Keyword(s):  
Triticum Aestivum ◽  
Electron Transport ◽  
Electron Acceptor ◽  
Photosynthetic Electron Transport ◽  
Significant Inhibition ◽  
Avena Fatua ◽  
Wild Oat ◽  
Leaf Chlorosis ◽  
Acceptor Activity ◽  
Proton Uptake

Experiments were conducted with isolated protoplasts of wild oat (Avena fatuaL. # AVEFA) and isolated chloroplasts of wild oat and wheat (Triticum aestivumL.), to determine if the methyl sulfate salt of difenzoquat (1,2-dimethyl-3,5-diphenyl-1H-pyrazolium) might influence photoreactions in these species. Difenzoquat did not affect CO2fixation, uncoupled electron transport, or proton uptake. At concentrations of 0.5 mM and 1 mM, difenzoquat caused a slight, but statistically significant, inhibition of photophosphorylation. Experiments assaying coupled electron transport indicated that inhibition of photophosphorylation occurred not through uncoupling, but by an energy-transfer inhibition. This same effect was observed in isolated mitocondria of both species, with about 50% inhibition of state 3 respiration rates occurring with 10 μM difenzoquat. However, no important differentials were observed in the relative susceptibilities of wheat and wild oat mitochondria. Difenzoquat also functioned as a weak autooxidizing electron acceptor in photosynthetic electron transport. Therefore, difenzoquat-induced leaf chlorosis and necrosis may result from a bipyridilium-type electron acceptor activity if sufficient herbicide is absorbed.

Inhibition of oxygen evolution by ivalin

1994 ◽  
Vol 72 (2) ◽  
pp. 177-181 ◽  
Author(s):  
Ernesto Bernal-Morales ◽  
Alfonso Romo De Vivar ◽  
Bertha Sanchez ◽  
Martha Aguilar ◽  
Blas Lotina-Hennsen
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Sesquiterpene Lactone ◽  
Oxygen Evolution ◽  
Electron Flow ◽  
Atp Synthesis ◽  
Naturally Occurring ◽  
Transport Inhibitor ◽  
Proton Uptake ◽  
Key Words Oxygen

The inhibition of ATP synthesis, proton uptake, and electron transport (basal, phosphorylating, and uncoupled) from water to methylviologen by ivalin (a naturally occurring sesquiterpene lactone in Zaluzania triloba and Iva microcephala) indicates that it acts as electron transport inhibitor. Since photosystem I and electron transport from DPC to QA were not affected, while the electron flow of uncoupled photosystem II from H2O to DAD and from water to silicomolybdate was inhibited, we concluded that the site of inhibition of ivalin is located at the oxygen evolution level. Key words: oxygen evolution, ivalin, photosynthesis, sesquiterpene lactone.

Studies about the Mechanism of Herbicidal Interaction with Photosystem II in Isolated Chloroplasts

1979 ◽  
Vol 34 (11) ◽  
pp. 1010-1014 ◽  
Author(s):  
Gernot Renger
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Excitation Energy ◽  
Electron Acceptor ◽  
Functional Organization ◽  
Regulatory Element ◽  
Release Kinetics ◽  
Acceptor Side ◽  
Receptor Sites ◽  
Isolated Chloroplasts

Abstract Based on the functional organization scheme of system-II-electron transport and its modification by different procedures a proteinaceous component enwrapping the redox components (plastoquinone molecules) of the acceptor side (thereby acting as regulatory element) is inferred to be the unique target for herbicidal interaction with system II. This proteinaceous component, which is attacked by trypsin, provides the receptor sites for the herbicides. Studies of the release kinetics in trypsinated chloroplasts of the inhibition of oxygen evolution with K3 [Fe (CN)6] as electron acceptor indicates, that there exists a binding area with different specific subreceptor sites rather than a unique binding site for the various types of inhibitors. Furthermore, trypsination of the proteinaceous component enhances the efficiency of the plastoquinone pool to act as a non-photochemical quencher for excitation energy.

Rewiring photosynthesis: a photosystem I-hydrogenase chimera that makes H2in vivo

2020 ◽  
Vol 13 (9) ◽  
pp. 2903-2914 ◽  
Author(s):  
Andrey Kanygin ◽  
Yuval Milrad ◽  
Chandrasekhar Thummala ◽  
Kiera Reifschneider ◽  
Patricia Baker ◽  
...  
Keyword(s):  
Electron Transport ◽  
Hydrogen Production ◽  
Photosystem I ◽  
Electron Transport Chain ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Photosynthetic Electron Transport Chain ◽  
Transport Chain

Photosystem I-hydrogenase chimera intercepts electron flow directly from the photosynthetic electron transport chain and directs it to hydrogen production.

DCMU-Induced Fluorescence Changes and Photodestruction of Pigments Associated with an Inhibition of Photosystem I Cyclic Electron Flow

1984 ◽  
Vol 39 (5) ◽  
pp. 351-353 ◽  
Author(s):  
Stuart M. Ridley ◽  
Peter Horton
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Photosystem I ◽  
Dose Response ◽  
Electron Flow ◽  
Cyclic Electron Flow ◽  
Cyclic Flow ◽  
Working Hypothesis ◽  
Dose Responses

Diuron (DCMU) induces the photodestruction of pigments, which is the initial herbicidal symptom. As a working hypothesis, it is proposed that this symptom can only be produced when the herbicide dose is sufficiently high to inhibit not only photosystem II electron transport almost completely, but also inhibit (through over oxidation) the natural cyclic electron flow associated with photosystem I as well. Using freshly prepared chloroplasts, studies of DCMU-induced fluorescence changes, and dose responses for inhibition of electron transport, have been compared with a dose response for the photodestruction of pigments in chloroplasts during 24 h illumination. Photodestruction of pigments coincides with the inhibition of cyclic flow.

Inhibition of Oxygen Evolution by Cacalol and Its Derivatives

1991 ◽  
Vol 46 (9-10) ◽  
pp. 777-780 ◽  
Author(s):  
B. Lotina-Hennsen ◽  
J. L. Roque-Reséndiz ◽  
M. Jiménez ◽  
M. Aguilar
Keyword(s):  
Electron Transport ◽  
Oxygen Evolution ◽  
Photosystem I ◽  
Atp Synthesis ◽  
The Other ◽  
Other Hand ◽  
Transport Inhibitors ◽  
Proton Uptake

Abstract The inhibition of ATP synthesis, proton uptake and electron transport (basal, phosphory-lating and uncoupled) from water to methylviologen indicates that cacalol and its derivatives act as electron transport inhibitors. Since on one hand photosystem I is not affected and elec­tron transport from DPC to QA is midly affected and on the other hand the electron transport from water to DCIP, and water to silicomolibdate are inhibited, we conclude that the site of inhibition of cacalol is located at the oxygen evolution level. Cacalol derivatives inhibit elec­tron flow between P680 to QA and probably also the QB site.

scholarly journals Quantitative electron-paramagnetic-resonance measurements of the electron-transfer components of the photosystem-I reaction centre. The reaction-centre chlorophyll (P700), the primary electron acceptor X and bound iron-sulphur centre A

1978 ◽  
Vol 170 (2) ◽  
pp. 373-378 ◽  
Author(s):  
P Heathcote ◽  
D L Williams-Smith ◽  
M C W Evans
Keyword(s):  
Free Radical ◽  
Electron Transport ◽  
Photosystem I ◽  
Electron Acceptor ◽  
Line Shape ◽  
Primary Electron ◽  
Reaction Centre ◽  
Electron Spins ◽  
Average Value ◽  
Primary Electron Acceptor

An e.p.r. spectrum of the reduced form of the electron-transport component (X), thought to be the primary electron acceptor of Photosystem I, was obtained. By using line-shape simulations of this component and the free-radical e.p.r. signal I of the oxidized reaction-centre chlorophyll (P700), it was possible to determine the ratio of the number of electron spins to which these signals correspond in Photosystem-I particles under a variety of conditions. On illumination at cryogenic temperatures of Photosystem-I preparations, in which both bound iron-sulphur centres A and B were reduced, the measured ratio of free radical to component X varied between 1.04 and 2.23, with an average value of 1.54 +/- 0.18 where a Gaussian line-shape is assumed for the component-X signal in the simulation. The error in this measurement is estimated to be up to 50%. In a similar way component X and centre A of the bound iron-sulphur protein were quantified, the ratio between these two components varying between 1.26 and 0.61 with an average value of 0.75 +/- 0.06. These results indicate that the quantitative relationship, in terms of net electron spins, between centre A, component X and P700 is of the order to be expected if component X is indeed the primary electron acceptor in Photosystem I and a component of the photosynthetic electron-transport chain.

scholarly journals Regulation of electron transport is essential for photosystem I stability and plant growth

2019 ◽  
Author(s):  
Mattia Storti ◽  
Anna Segalla ◽  
Marco Mellon ◽  
Alessandro Alboresi ◽  
Tomas Morosinotto
Keyword(s):  
Electron Transport ◽  
Photosystem I ◽  
Nadh Dehydrogenase ◽  
Physcomitrella Patens ◽  
Electron Flow ◽  
Photosynthetic Electron Transport ◽  
Type I ◽  
Growth Reduction ◽  
Light Regimes ◽  
Photosynthetic Organisms

AbstractLife depends on the ability of photosynthetic organisms to exploit sunlight to fix carbon dioxide into biomass. Photosynthesis is modulated by pathways such as cyclic and pseudocyclic electron flow (CEF and PCEF). CEF transfers electrons from photosystem I to the plastoquinone pool according to two mechanisms, one dependent on proton gradient regulators (PGR5/PGRL1) and the other on the type I NADH dehydrogenase (NDH) complex. PCEF uses electrons from photosystem I to reduce oxygen; in several groups of photosynthetic organisms but not in angiosperms, it is sustained by flavodiiron proteins (FLVs). PGR5/PGRL1, NDH and FLVs are all active in the moss Physcomitrella patens, and mutants depleted in these proteins show phenotypes under specific light regimes. Here, we demonstrated that CEF and PCEF exhibit strong functional overlap and that when one protein component is depleted, the others can compensate for most of the missing activity. When multiple mechanisms are simultaneously inactivated, however, plants show damage to photosystem I and strong growth reduction, demonstrating that mechanisms for the modulation of photosynthetic electron transport are indispensable.

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