TY - JOUR
T1 - Mitochondrial alternative pathway-associated photoprotection of photosystem II is related to the photorespiratory pathway
AU - Watanabe, Chihiro K.A.
AU - Yamori, Wataru
AU - Takahashi, Shunichi
AU - Terashima, Ichiro
AU - Noguchi, Ko
N1 - Publisher Copyright:
© The Author 2016.
PY - 2016
Y1 - 2016
N2 - 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 (Fv/Fm) 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 350μmol m-2s-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 O2 levels, the decline in Fv/Fm 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.
AB - 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 (Fv/Fm) 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 350μmol m-2s-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 O2 levels, the decline in Fv/Fm 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.
KW - Alternative oxidase
KW - Alternative pathway
KW - Arabidopsis thaliana
KW - Photoinhibition
KW - Photorespiratory pathway
KW - Respiration
UR - http://www.scopus.com/inward/record.url?scp=84983002000&partnerID=8YFLogxK
U2 - 10.1093/pcp/pcw036
DO - 10.1093/pcp/pcw036
M3 - Article
SN - 0032-0781
VL - 57
SP - 1426
EP - 1431
JO - Plant and Cell Physiology
JF - Plant and Cell Physiology
IS - 7
ER -