TY - JOUR
T1 - Over-reduced states of the Mn-cluster in cucumber leaves induced by dark-chilling treatment
AU - Higuchi, Mieko
AU - Noguchi, Takumi
AU - Sonoike, Kintake
N1 - Funding Information:
We thank Prof. Itzhak Ohad and Dr. Nir Karen without whom we would never have started this study. We also thank Prof. Amarendra Narayan Misra for critically reading the manuscript. This research was supported in part by a Grant-in-Aid for Scientific Research (B) to K.S. and for Scientific Research (C) to T.N. from the Japan Society for the Promotion of Science.
PY - 2003/7/10
Y1 - 2003/7/10
N2 - Oxygen evolution is inhibited when leaves of chilling-sensitive plants like cucumber are treated at 0°C in the dark. The activity is restored by moderate illumination at room temperature. We examined the changes in the redox state of the Mn-cluster in cucumber leaves in the processes of dark-chilling inhibition and subsequent light-induced reactivation by means of thermoluminescence (TL). A TL B-band arising from S2QB- charge recombination in PSII was observed upon single-flash illumination of untreated leaves, whereas four flashes were required to yield the B-band after dark-chilling treatment for 24 h. This three-step delay indicates that over-reduced states of the Mn-cluster such as the S-2 state were formed during the treatment. Fitting analysis of the flash-number dependence of the TL intensities showed that the Mn-cluster was more reduced with a longer period of the treatment and that S-3 was the lowest S-state detectable in the dark-chilled leaves. Measurements of the Mn content by atomic absorption spectroscopy showed that Mn atoms were gradually released from PSII during the dark-chilling treatment but re-bound to PSII by illumination at 30°C. Thus, dark-chilling inhibition of oxygen evolution can be ascribed to the disintegration of the Mn-cluster due to its over-reduction. The observation of the S-3 state in the present in vivo system strongly suggests that S-3, which has been observed only by addition of exogenous reductants into in vitro preparations, is indeed a redox intermediate of the Mn-cluster in the processes of its disintegration and photoactivation.
AB - Oxygen evolution is inhibited when leaves of chilling-sensitive plants like cucumber are treated at 0°C in the dark. The activity is restored by moderate illumination at room temperature. We examined the changes in the redox state of the Mn-cluster in cucumber leaves in the processes of dark-chilling inhibition and subsequent light-induced reactivation by means of thermoluminescence (TL). A TL B-band arising from S2QB- charge recombination in PSII was observed upon single-flash illumination of untreated leaves, whereas four flashes were required to yield the B-band after dark-chilling treatment for 24 h. This three-step delay indicates that over-reduced states of the Mn-cluster such as the S-2 state were formed during the treatment. Fitting analysis of the flash-number dependence of the TL intensities showed that the Mn-cluster was more reduced with a longer period of the treatment and that S-3 was the lowest S-state detectable in the dark-chilled leaves. Measurements of the Mn content by atomic absorption spectroscopy showed that Mn atoms were gradually released from PSII during the dark-chilling treatment but re-bound to PSII by illumination at 30°C. Thus, dark-chilling inhibition of oxygen evolution can be ascribed to the disintegration of the Mn-cluster due to its over-reduction. The observation of the S-3 state in the present in vivo system strongly suggests that S-3, which has been observed only by addition of exogenous reductants into in vitro preparations, is indeed a redox intermediate of the Mn-cluster in the processes of its disintegration and photoactivation.
KW - Cucumber (Cucumis sativus L.)
KW - Dark-chilling
KW - Mn-cluster
KW - Oxygen-evolving complex
KW - S-state
KW - Thermoluminescence
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U2 - 10.1016/S0005-2728(03)00044-6
DO - 10.1016/S0005-2728(03)00044-6
M3 - Article
C2 - 12837547
AN - SCOPUS:0038433215
SN - 0005-2728
VL - 1604
SP - 151
EP - 158
JO - Biochimica et Biophysica Acta - Bioenergetics
JF - Biochimica et Biophysica Acta - Bioenergetics
IS - 3
ER -