TY - JOUR
T1 - Oxidation of P700 induces alternative electron flow in photosystem I in wheat leaves
AU - Kadota, Kanae
AU - Furutani, Riu
AU - Makino, Amane
AU - Suzuki, Yuji
AU - Wada, Shinya
AU - Miyake, Chikahiro
N1 - Funding Information:
This research was funded by the Core Research for Environmental Science and Technology (Scientific Research Grant No. AL65D21010 to C.M.).
Funding Information:
Funding: This research was funded by the Core Research for Environmental Science and Technology (Scientific Research Grant No. AL65D21010 to C.M.).
Publisher Copyright:
© 2019 by the authors. Licensee MDPI, Basel, Switzerland.
PY - 2019/6
Y1 - 2019/6
N2 - Oxygen (O2)-evolving photosynthetic organisms oxidize the reaction center chlorophyll, P700, in photosystem I (PSI) to suppress the production of reactive oxygen species. The oxidation of P700 is accompanied by alternative electron flow in PSI (AEF-I), which is not required for photosynthetic linear electron flow (LEF). To characterize AEF-I, we compared the redox reactions of P700 and ferredoxin (Fd) during the induction of carbon dioxide (CO2) assimilation in wheat leaves, using dark-interval relaxation kinetics analysis. Switching on an actinic light (1000 μmol photons m−2 s−1) at ambient CO2 partial pressure of 40 Pa and ambient O2 partial pressure of 21 kPa gradually oxidized P700 (P700+) and enhanced the reduction rate of P700+ (vP700) and oxidation rate of reduced Fd (vFd). The vFd showed a positive linear relationship with an apparent photosynthetic quantum yield of PSII (Y[II]) originating at point zero; the redox turnover of Fd is regulated by LEF via CO2 assimilation and photorespiration. The vP700 also showed a positive linear relationship with Y(II), but the intercept was positive, not zero. That is, the electron flux in PSI included the electron flux in AEF-I in addition to that in LEF. This indicates that the oxidation of P700 induces AEF-I. We propose a possible mechanism underlying AEF-I and its physiological role in the mitigation of oxidative damage.
AB - Oxygen (O2)-evolving photosynthetic organisms oxidize the reaction center chlorophyll, P700, in photosystem I (PSI) to suppress the production of reactive oxygen species. The oxidation of P700 is accompanied by alternative electron flow in PSI (AEF-I), which is not required for photosynthetic linear electron flow (LEF). To characterize AEF-I, we compared the redox reactions of P700 and ferredoxin (Fd) during the induction of carbon dioxide (CO2) assimilation in wheat leaves, using dark-interval relaxation kinetics analysis. Switching on an actinic light (1000 μmol photons m−2 s−1) at ambient CO2 partial pressure of 40 Pa and ambient O2 partial pressure of 21 kPa gradually oxidized P700 (P700+) and enhanced the reduction rate of P700+ (vP700) and oxidation rate of reduced Fd (vFd). The vFd showed a positive linear relationship with an apparent photosynthetic quantum yield of PSII (Y[II]) originating at point zero; the redox turnover of Fd is regulated by LEF via CO2 assimilation and photorespiration. The vP700 also showed a positive linear relationship with Y(II), but the intercept was positive, not zero. That is, the electron flux in PSI included the electron flux in AEF-I in addition to that in LEF. This indicates that the oxidation of P700 induces AEF-I. We propose a possible mechanism underlying AEF-I and its physiological role in the mitigation of oxidative damage.
KW - P700
KW - charge recombination
KW - cyclic electron flow
KW - ferredoxin
KW - photosystem I
KW - reactive oxygen species
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U2 - 10.3390/plants8060152
DO - 10.3390/plants8060152
M3 - Article
AN - SCOPUS:85070192799
SN - 2223-7747
VL - 8
JO - Plants
JF - Plants
IS - 6
M1 - 152
ER -