Inhibition of CO2 fixation by iodoacetamide stimulates cyclic electron flow and non-photochemical quenching upon far-red illumination.
Photosynth Res
; 115(1): 55-63, 2013 May.
Article
em En
| MEDLINE
| ID: mdl-23625532
ABSTRACT
The Benson-Calvin cycle enzymes are activated in vivo when disulfide bonds are opened by reduction via the ferredoxin-thioredoxin system in chloroplasts. Iodoacetamide reacts irreversibly with free -SH groups of cysteine residues and inhibits the enzymes responsible for CO2 fixation. Here, we investigate the effect of iodoacetamide on electron transport, when infiltrated into spinach leaves. Using fluorescence and absorption spectroscopy, we show that (i) iodoacetamide very efficiently blocks linear electron flow upon illumination of both photosystems (decrease in the photochemical yield of photosystem II) and (ii) iodoacetamide favors cyclic electron flow upon light excitation specific to PSI. These effects account for an NPQ formation even faster in iodoacetamide under far-red illumination than in the control under saturating light. Such an increase in NPQ is dependent upon the proton gradient across the thylakoid membrane (uncoupled by nigericin addition) and PGR5 (absent in Arabidopsis pgr5 mutant). Iodoacetamide very tightly insulates the electron current at the level of the thylakoid membrane from any electron leaks toward carbon metabolism, therefore, providing choice conditions for the study of cyclic electron flow around PSI.
Texto completo:
1
Coleções:
01-internacional
Temas:
Geral
Base de dados:
MEDLINE
Assunto principal:
Fotossíntese
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Dióxido de Carbono
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Arabidopsis
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Spinacia oleracea
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Iodoacetamida
Idioma:
En
Revista:
Photosynth Res
Assunto da revista:
METABOLISMO
Ano de publicação:
2013
Tipo de documento:
Article
País de afiliação:
França