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Front. Plant Sci. | doi: 10.3389/fpls.2018.00239

Cyclic electron flow around photosystem I promotes ATP synthesis possibly helping the rapid repair of photodamaged photosystem II at low light

  • 1Kunming Institute of Botany, Kunming Institute of Botany (CAS), China
  • 2Yunnan Agricultural University, China

In higher plants, moderate photoinhibition of photosystem II (PSII) leads to a stimulation of cyclic electron flow (CEF) at low light, which is accompanied by an increase in the P700 oxidation ratio. However, the specific role of CEF stimulation at low light is not well known. Furthermore, the mechanism underlying this increase in P700 oxidation ratio at low light is unclear. To address these questions, intact leaves of the shade-adapted plant Panax notoginseng were treated at 2258 μmol photons m-2 s-1 for 30 min to induce PSII photoinhibition. Before and after this high-light treatment, PSI and PSII activity, the energy quenching in PSII, the redox state of PSI and proton motive force (pmf) at a low light of 54 μmol photons m-2 s-1 were determined at the steady state. After high-light treatment, electron flow through PSII (ETRII) significantly decreased but CEF was remarkably stimulated. The P700 oxidation ratio significantly increased but non-photochemical quenching changed negligibly. Concomitantly, the total pmf decreased significantly and the proton gradient (ΔpH) across the thylakoid membrane remained stable. Furthermore, the P700 oxidation ratio was negatively correlated with the value of ETRII. These results suggest that upon PSII photoinhibition, CEF is stimulated to increase the ATP synthesis, facilitating the rapid repair of photodamaged PSII. The increase in P700 oxidation ratio at low light cannot be explained by the change in pmf, but is primarily controlled by electron transfer from PSII.

Keywords: ATP synthesis, cyclic electron flow, Linear electron flow, proton motive force, PSII photoinhibition, P700 oxidation ratio

Received: 10 Jan 2018; Accepted: 09 Feb 2018.

Edited by:

Marian Brestic, Slovak University of Agriculture, Slovakia

Reviewed by:

Lorenzo Ferroni, University of Ferrara, Italy
Xinghong Yang, shandong agricultural university, China
Xiangnan Li, Northeast Institute of Geography and Agroecology (CAS), China  

Copyright: © 2018 Huang, Yang, Zhang and Liu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Wei Huang, Kunming Institute of Botany (CAS), Kunming Institute of Botany, Kunming, China, huangwei@mail.kib.ac.cn