Document Detail

Distinct roles of the cytochrome pathway and alternative oxidase in leaf photosynthesis.
MedLine Citation:
PMID:  16239307     Owner:  NLM     Status:  MEDLINE    
In illuminated leaves, mitochondria are thought to play roles in optimizing photosynthesis. However, the roles of the cytochrome pathway (CP) and alternative oxidase (AOX) in photosynthesis, in particular in the redox state of the photosynthetic electron transport chain, are not separately characterized. We examined the effects of specific inhibition of two respiratory pathways, CP and AOX, on photosynthetic oxygen evolution and the redox state of the photosynthetic electron transport chain in broad bean (Vicia faba L.) leaves under various light intensities. Under saturating photosynthetic photon flux density (PPFD; 700 micromol photon m(-2) s(-1)), inhibition of either pathway caused a decrease in the steady-state levels of the photosynthetic O(2) evolution rate and the PSII operating efficiency, Phi(II). Because these inhibitors, at the concentrations applied to the leaves, had little effect on photosynthesis in the intact chloroplasts, two respiratory pathways are essential for maintenance of high photosynthetic rates at saturating PPFD. CP or AOX inhibition affected to Chl fluorescence parameters (e.g. photochemical quenching and non-photochemical quenching) differently, suggesting that CP and AOX contribute to photosynthesis in different ways. At low PPFD (100 micromol photon m(-2) s(-1)), only the inhibition of AOX, not CP, lowered the photosynthetic rate and Phi(II). AOX inhibition also decreased the Phi(II)/Phi(I) ratio even at low PPFD levels. These data suggest that AOX inhibition caused the over-reduction of the photosynthetic electron transport chain and induced the cyclic electron flow around PSI (CEF-PSI) even at the low PPFD. Based on these results, we discuss possible roles for CP and AOX in the light.
Keisuke Yoshida; Ichiro Terashima; Ko Noguchi
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2005-10-20
Journal Detail:
Title:  Plant & cell physiology     Volume:  47     ISSN:  0032-0781     ISO Abbreviation:  Plant Cell Physiol.     Publication Date:  2006 Jan 
Date Detail:
Created Date:  2006-02-09     Completed Date:  2006-04-10     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9430925     Medline TA:  Plant Cell Physiol     Country:  Japan    
Other Details:
Languages:  eng     Pagination:  22-31     Citation Subset:  IM    
Department of Biology, Graduate School of Science, Osaka University, Toyonaka, Japan.
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MeSH Terms
Antimycin A / pharmacology
Chlorophyll / metabolism
Cytochromes / metabolism*
Electron Transport / drug effects
Models, Biological
Oxidoreductases / metabolism*
Oxygen Consumption / drug effects
Photosynthesis / drug effects,  physiology*
Photosystem II Protein Complex / metabolism
Plant Leaves / drug effects,  metabolism*,  radiation effects
Salicylamides / pharmacology
Vicia faba / drug effects,  metabolism,  radiation effects
Reg. No./Substance:
0/Cytochromes; 0/Photosystem II Protein Complex; 0/Salicylamides; 1406-65-1/Chlorophyll; 642-15-9/Antimycin A; 89-73-6/salicylhydroxamic acid; EC 1.-/Oxidoreductases; EC 1.-/alternative oxidase

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