TY - JOUR
T1 - Photosynthetic electron transport and proton flux under moderate heat stress
AU - Zhang, Ru
AU - Sharkey, Thomas D.
N1 - Funding Information:
Acknowledgments We thank Dr. Toshiharu Shikanai and Dr. Archie Portis for mutant seeds. Dr. Stephen Schrader and Dr. Dafu Wang are thanked for the help on gas exchange machine build-up and the suggestions on planting mutants, respectively. We are grateful to Dr. David Kramer for excellent advice on our ECS measurements. We also appreciate the chlorophyll fluorescence equipment loaned by Dr. Robert Wise and the information from Dr. Cécile Ané about statistical analysis. The project was supported by the National Research Initiative of the USDA Cooperative State Research, Education and Extension Service, grant number 2004-35100-14860.
PY - 2009/4
Y1 - 2009/4
N2 - Moderate heat stress has been reported to increase PSI cyclic electron flow (CEF). We subjected leaves of Arabidopsis (Arabidopsis thaliana) mutants disrupted in the regulation of one or the other pathway of CEF flow-crr2 (chlororespiratory reduction, deficient in regulation of chloroplast NAD(P)H dehydrogenase-dependent CEF) and pgr5 (proton gradient regulation, proposed to have reduced efficiency of antimycin-A-sensitive-CEF regulation) to moderate heat stress. Light-adapted leaves were switched from 23 to 40°C in 2 min. Gas exchange, chlorophyll fluorescence, the electrochromic shift (ECS), and P700 were measured. Photosynthesis of crr2 and pgr5 was more sensitive to heat and had less ability to recover than the genetic background gl. The proton conductance in light was increased by heat and it was twice as much in pgr5, which had much smaller light-induced proton motive force. We confirmed that P700 becomes more reduced at high temperature and show that, in contrast, the proportion of PSII open centers (with Q A oxidized) increases. The two mutants had much slower P700+ reduction rate during and after heat than gl. The proportion of light absorbed by PSI versus PSII was increased in gl and crr2 during and after heat treatment, but not in pgr5. We propose that heat alters the redox balance away from PSII and toward PSI and that the regulation of CEF helps photosynthesis tolerate heat stress.
AB - Moderate heat stress has been reported to increase PSI cyclic electron flow (CEF). We subjected leaves of Arabidopsis (Arabidopsis thaliana) mutants disrupted in the regulation of one or the other pathway of CEF flow-crr2 (chlororespiratory reduction, deficient in regulation of chloroplast NAD(P)H dehydrogenase-dependent CEF) and pgr5 (proton gradient regulation, proposed to have reduced efficiency of antimycin-A-sensitive-CEF regulation) to moderate heat stress. Light-adapted leaves were switched from 23 to 40°C in 2 min. Gas exchange, chlorophyll fluorescence, the electrochromic shift (ECS), and P700 were measured. Photosynthesis of crr2 and pgr5 was more sensitive to heat and had less ability to recover than the genetic background gl. The proton conductance in light was increased by heat and it was twice as much in pgr5, which had much smaller light-induced proton motive force. We confirmed that P700 becomes more reduced at high temperature and show that, in contrast, the proportion of PSII open centers (with Q A oxidized) increases. The two mutants had much slower P700+ reduction rate during and after heat than gl. The proportion of light absorbed by PSI versus PSII was increased in gl and crr2 during and after heat treatment, but not in pgr5. We propose that heat alters the redox balance away from PSII and toward PSI and that the regulation of CEF helps photosynthesis tolerate heat stress.
KW - Chlorophyll fluorescence
KW - Cyclic electron transport around PSI
KW - Electrochromic shift
KW - Gas exchange
KW - Moderate heat stress
KW - P700 measurement
UR - http://www.scopus.com/inward/record.url?scp=67349122643&partnerID=8YFLogxK
U2 - 10.1007/s11120-009-9420-8
DO - 10.1007/s11120-009-9420-8
M3 - Article
C2 - 19343531
AN - SCOPUS:67349122643
SN - 0166-8595
VL - 100
SP - 29
EP - 43
JO - Photosynthesis Research
JF - Photosynthesis Research
IS - 1
ER -