Journal
PLANT AND CELL PHYSIOLOGY
Volume 57, Issue 7, Pages 1426-1431Publisher
OXFORD UNIV PRESS
DOI: 10.1093/pcp/pcw036
Keywords
Alternative oxidase; Alternative pathway; Arabidopsis thaliana; Photoinhibition; Photorespiratory pathway; Respiration
Categories
Funding
- Ministry of Education, Culture, Sports, Science and Technology of Japan [25440127]
- Grants-in-Aid for Scientific Research [26291055, 25440127] Funding Source: KAKEN
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Respiratory electron transport has two ubiquinol-oxidizing pathways, the cytochrome pathway (CP) and the alternative pathway (AP). The AP, which is catalyzed by the alternative oxidase (AOX), is energetically wasteful but may alleviate PSII photoinhibition under light conditions excessive for photosynthesis. However, its mechanism remains unknown. We used Arabidopsis aox1a mutants lacking AOX activity and studied the mutation's effects on photoinhibition by measuring the decrease in the maximum quantum yield of PSII (F-v/F-m) after high light exposure. Since the CP compensates for the lack of AOX, we monitored the extent of photoinhibition under conditions where CP activity is partially inhibited by antimycin A. When leaves were exposed to high light at 350 mmol m(-2) s(-1), the decline in Fv/Fm was significantly faster in the aox1a mutants than in the wild type. However, under conditions where photorespiration was suppressed by high CO2 or low O-2 levels, the decline in F-v/F-m was suppressed in the aox1a mutants, but not in the wild type, making the difference between the wild type and mutants small. Our results demonstrate that the lack of the AP causes an acceleration of PSII photoinhibition in relation to the photorespiratory pathway, suggesting that the AP can support the activity of the photorespiratory pathway under high light conditions.
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