Plant and Cell Physiology, 2002, Vol. 43, No. 8 951-957
© 2002 Oxford University Press
Cyclic Electron Flow within PSII Functions in Intact Chloroplasts from Spinach Leaves
1 Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, 6-10-1, Hakozaki, Higashi-ku, Fukuoka, 812-8581 Japan
2 Graduate School of Biological Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0101 Japan
Using thylakoid membranes, we previously demonstrated that accumulated electrons in the photosynthetic electron transport system induces the electron flow from the acceptor side of PSII to its donor side only in the presence of a pH gradient (
pH) across the thylakoid membranes. This electron flow has been referred to as cyclic electron flow within PSII (CEF-PSII) [Miyake and Yokota (2001) Plant Cell Physiol. 42: 508]. In the present study, we examined whether CEF-PSII operates in isolated intact chloroplasts from spinach leaves, by correlating the quantum yield of PSII [
(PSII)] with the activity of the linear electron flow [V(O2)]. The addition of the protonophore nigericin to the intact chloroplasts decreased (PSII), but increased V(O2), and relative electron flux in PSII [(PSII) x PFD] and V(O2) were proportional to one another. (PSII) x PFD at a given V(O2) was much higher in the presence of pH than that in its absence. These effects of nigericin on the relationship between (PSII) x PFD and V(O2) are consistent with those previously observed in thylakoid membranes, indicating the occurrence of CEF-PSII also in intact chloroplasts. In the presence of pH, CEF-PSII accounted for the excess electron flux in PSII that could not be attributed to photosynthetic linear electron flow. The activity of CEF-PSII increased with increased light intensity and almost corresponded to that of the water–water cycle (WWC), implying that CEF-PSII can dissipate excess photon energy in cooperation with WWC to protect PSII from photoinhibition under limited photosynthesis conditions.
3 Corresponding author: E-mail, cmiyake@brs.kyushu-u.ac.jp; Fax, +81-92-642-4424.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  K. Asada Production and Scavenging of Reactive Oxygen Species in Chloroplasts and Their Functions Plant Physiology, June 1, 2006; 141(2): 391 - 396. [Full Text] [PDF]
|
|
|
|
 |
|
 C. Miyake, Y. Shinzaki, M. Nishioka, S. Horiguchi, and K.-I. Tomizawa Photoinactivation of Ascorbate Peroxidase in Isolated Tobacco Chloroplasts: Galdieria partita APX Maintains the Electron Flux through the Water-Water Cycle in Transplastomic Tobacco Plants Plant Cell Physiol., February 1, 2006; 47(2): 200 - 210. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Miyake and M. Okamura Cyclic Electron Flow within PSII Protects PSII from its Photoinhibition in Thylakoid Membranes from Spinach Chloroplasts Plant Cell Physiol., April 15, 2003; 44(4): 457 - 462. [Abstract] [Full Text] [PDF]
|
|