Paraquat-Catalyzed Photodestructions in Subchloroplast Particles are Independent on Photosynthetic Electron Transport

1980 ◽  
Vol 35 (3-4) ◽  
pp. 303-307 ◽  
Author(s):  
E. F. Elstner ◽  
E. Lengfelder ◽  
G. Kwiatkowski
Keyword(s):  
Superoxide Dismutase ◽  
Electron Transport ◽  
Superoxide Radical ◽  
Photosynthetic Electron Transport ◽  
Activated Oxygen ◽  
Ethane Production ◽  
Chlorophyll Bleaching ◽  
Endogenous Substrates ◽  
Ethane Formation ◽  
Active Substances

Abstract Light dependent ethane formation and chlorophyll bleaching in isolated chloroplast lamellae are enhanced by either methylviologen or α-linolenic acid. Both ethane formation and chloro­phyll bleaching are also enhanced in chloroplast particles deficient in photosynthetic electron transport, e. g. after aging, heat treatment or digitonin fragmentation. Ethane formation by sub­ chloroplast particles from endogenous substrates in the presence of methylviologen is inhibited by superoxide dismutase or by a penicillamine copper complex exhibiting superoxide dismutase activity whereas chlorophyll bleaching is enhanced by superoxide dismutase - active substances. Maximal rates of ethane formation in subchloroplast particles are observed when more than 50% of the chlorophyll is bleached and continues after 98% chlorophyll bleaching. This result indicated that methylviologen -stimulated ethane production in subchloroplast particles is not de­pendent on photosynthetic electron transport but involves “activated oxygen” - species like the superoxide radical ion, generated by a light receptor derived from the pigmentsystem of photo­ system I or activated after its destruction.

Superoxide-and Ethane-Formation in Subchloroplast Particles: Catalysis by Pyridinium Derivatives

1980 ◽  
Vol 35 (9-10) ◽  
pp. 770-775 ◽  
Author(s):  
E. F. Elstner ◽  
H. P. Fischer ◽  
W. Osswald ◽  
G. Kwiatkowski
Keyword(s):  
Electron Transport ◽  
Photosystem I ◽  
Photosynthetic Electron Transport ◽  
Redox Potentials ◽  
Light Reaction ◽  
Pyridinium Bromide ◽  
Superoxide Formation ◽  
Fatty Acid Peroxidation ◽  
Chlorophyll Bleaching ◽  
Ethane Formation

Abstract Oxygen reduction by chloroplast lamellae is catalyzed by low potential redox dyes with E′0 values between -0 .3 8 V and -0 .6 V. Compounds of E′0 values of -0 .6 7 V and lower are inactive. In subchloroplast particles with an active photosystem I but devoid of photosynthetic electron transport between the two photosystems, the active redox compounds enhance chlorophyll bleaching, superoxide formation and ethane production independent on exogenous substrates or electron donors. The activities of these compounds decrease with decreasing redox potential, with one exception: 1-methyl-4,4′-bipyridini urn bromide with an E′0 value of lower -1 V (and thus no electron acceptor of photosystem I in chloroplast lamellae with intact electron transport) stimulates light dependent superoxide formation and unsaturated fatty acid peroxidation in sub­ chloroplast particles, maximal rates appearing after almost complete chlorophyll bleaching. Since this activity is not visible with compounds with redox potentials below -0 .6 V lacking the nitrogen atom at the 1-position of the pyridinium substituent, we assume that 1 -methyl-4,4′-bi-pyridinium bromide is “activated” by a yet unknown light reaction.

Formation mechanisms of superoxide radical and hydrogen peroxide in chloroplasts, and factors determining the signalling by hydrogen peroxide

2018 ◽  
Vol 45 (2) ◽  
pp. 102 ◽  
Author(s):  
Boris N. Ivanov ◽  
Maria M. Borisova-Mubarakshina ◽  
Marina A. Kozuleva
Keyword(s):  
Hydrogen Peroxide ◽  
Electron Transport ◽  
Thylakoid Membrane ◽  
Electron Transport Chain ◽  
Superoxide Radical ◽  
Photosynthetic Electron Transport ◽  
Formation Mechanisms ◽  
H2o2 Production ◽  
Photosynthetic Electron Transport Chain ◽  
Transport Chain

Reduction of O2 molecule to superoxide radical, O2•−, in the photosynthetic electron transport chain is the first step of hydrogen peroxide, H2O2, production in chloroplasts in the light. The mechanisms of O2 reduction by ferredoxin, by the components of the plastoquinone pool, and by the electron transfer cofactors in PSI are analysed. The data indicating that O2•− and H2O2 can be produced both outside and within thylakoid membrane are presented. The H2O2 production in the chloroplast stroma is described as a result of either dismutation of O2•− or its reduction by stromal reductants. Formation of H2O2 within thylakoid membrane in the reaction of O2•− with plastohydroquinone is examined. The significance of both ways of H2O2 formation for specificity of the signal being sent by photosynthetic electron transport chain to cell adaptation systems is discussed.

Diethyldithiocarbamate, a New Photosystem I Electron Donor of Mehler-Type Hill Reactions

1986 ◽  
Vol 41 (9-10) ◽  
pp. 861-866 ◽  
Author(s):  
Brad L. Upham ◽  
Kriton K. Hatzios
Keyword(s):  
Superoxide Dismutase ◽  
Electron Transport ◽  
Electron Donor ◽  
Photosystem I ◽  
Photosynthetic Electron Transport ◽  
Mehler Reaction ◽  
Plastoquinone Pool ◽  
Electron Donation

Abstract Diethyldithiocarbamate (DEDTC) does not accept electrons from the photosynthetic electron transport (PET) but can donate electrons to a photosystem I (PSI) Mehler reaction in the pres­ence of the following PET inhibitors: DCMU. DBMIB, and bathophenanthroline. It cannot photoreduce PSI in the presence of cyanide, a PET inhibitor. These data indicate that the site of electron donation is after the plastoquinone pool. Ascorbate is not required for the ability of DEDTC to donate electrons to PSI. There is no photoreductant activity by DEDTC inferredoxin/NADP Hill reactions. Superoxide dismutase inhibits DEDTC/DCMU or bathophenanthroline→methylviologen/O2 Mehler reaction. Catalase does not recover the consumed O2 from a DEDTC/DCMU→methylviologen/O2 Mehler reaction, indicating O2- has not been dismutating into H2O2. These results indicate that superoxide is required for DEDTC ability to donate electrons, therefore DEDTC is limited only to Mehler-type reactions.

Enhancement of Chloroplast Photooxidations with Photosynthesis-Inhibiting Herbicides and Protection with NADH or NADPH

Weed Science ◽  
1978 ◽  
Vol 26 (5) ◽  
pp. 440-443 ◽  
Author(s):  
C. N. Giannopolitis ◽  
G. S. Ayers
Keyword(s):  
Lipid Peroxidation ◽  
Electron Transport ◽  
Hordeum Vulgare ◽  
Photosynthetic Electron Transport ◽  
Intact Chloroplasts ◽  
Chlorophyll Bleaching ◽  
Additional Support ◽  
Reducing Potential

Representative herbicides of the substituted ureas, uracils,s-triazines, benzonitriles, and bipyridyls, which are potent inhibitors of photosynthetic electron transport, markedly accelerated photooxidations (chlorophyll bleaching and lipid peroxidation) normally occurring in isolated intact chloroplasts. Other herbicides, which are not potent inhibitors of photosynthesis, did not accelerate photooxidations. The photooxidations, whether in the presence or absence of herbicides, were completely prevented by exogenously supplied NADH or NADPH but not by sucrose or mannitol. Herbicide-induced injury to barley(Hordeum vulgareL.) seedlings treated with paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) was diminished by allowing the seedlings to absorb NADPH. These results provide additional support to the hypothesis that depletion of the source of reducing potential (NADPH) is responsible for chloroplast photooxidations and plant death following treatment with photosynthesis-inhibiting herbicides.

Action of EMD-IT 5914 on Chloroplasts

Weed Science ◽  
1978 ◽  
Vol 26 (3) ◽  
pp. 292-296 ◽  
Author(s):  
K. J. Kunert ◽  
P. Böger
Keyword(s):  
Electron Transport ◽  
Oxygen Evolution ◽  
Direct Effect ◽  
Aminolevulinic Acid ◽  
Photosynthetic Electron Transport ◽  
Carotenoid Biosynthesis ◽  
Secondary Process ◽  
Chloroplast Pigments ◽  
Unicellular Algae ◽  
Chlorophyll Bleaching

The experimental herbicide EMD-IT 5914 [difunon, 5-dimethyl-amino-methylene-2-oxo-4-phenyl-2,5-dihydrofurane-carbonitrile-(3)] was applied to unicellular algae and its effect on growth, oxygen evolution and photosynthetic electron transport measured. Inhibition of biosynthesis of chloroplast pigments was evaluated in relation to the activities of porphobilinogenase and δ-aminolevulinic acid dehydratase. The only direct effect of the herbicide was an inhibition of carotenoid biosynthesis but not of photosynthetic electron transport or enzymic activities connected with porphyrin biosynthesis. Chlorophyll bleaching is considered to be a secondary process.

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