Cyclic electron flow around photosystem I is essential for photosynthesis

  title={Cyclic electron flow around photosystem I is essential for photosynthesis},
  author={Yuri N Munekage and Mihoko Hashimoto and Chikahiro Miyake and Ken-ichi Tomizawa and Tsuyoshi Endo and Masao Tasaka and Toshiharu Shikanai},
Photosynthesis provides at least two routes through which light energy can be used to generate a proton gradient across the thylakoid membrane of chloroplasts, which is subsequently used to synthesize ATP. In the first route, electrons released from water in photosystem II (PSII) are eventually transferred to NADP+ by way of photosystem I (PSI). This linear electron flow is driven by two photochemical reactions that function in series. The cytochrome b6f complex mediates electron transport… 

Characterization of the Novel Photosynthetic Protein PPP7 involved in Cyclic Electron Flow around PSI

  • G. Corso
  • Biology, Environmental Science
  • 2007
CEF is enhanced in the Arabidopsis psad1 and psae1 mutants with a defect in photosystem I oxidation in contrast to the cyanobacterial psae mutant which exhibits an decreased CEF, pointing to fundamental mechanistic differences in the cyclic electron flow of cyanobacteria and vascular plants.

A Supercomplex of Cytochrome bf and Photosystem I for Cyclic Electron Flow

This review focuses on a recent report on the super-supercomplex that is composed of the cytochrome b6f complex, photosystem I with its own light-harvesting complex, the light- Harvesting complex for photosystem II, and the ferredoxin-NADPH oxidoreductase, which exhibits cyclic electron flow in the green unicellular alga Chlamydomonas reinhardtii.

Physiological Functions of Cyclic Electron Transport Around Photosystem I in Sustaining Photosynthesis and Plant Growth.

This review summarizes the possible functions and importance of the two pathways of PSI cyclic electron transport and proposes a major pathway mediated by the chloroplast NADH dehydrogenase-like (NDH) complex.

Regulatory network of proton motive force: contribution of cyclic electron transport around photosystem I

This mechanism sacrifices homeostasis of the thylakoid lumen pH, seriously disturbing the pH-dependent regulation of photosynthetic electron transport, induction of qE, and downregulation of the cytochrome b6f complex.

Chapter 22 Regulation of Photosynthetic Electron Transport

The photosynthetic machinery of plants has two conflicting functions. It has to perform at maximum efficiency under light-limited conditions, but has to avoid photo-damage when the incoming light

Regulation of electron transport is essential for photosystem I stability and plant growth

It is demonstrated that CEF and PCEF exhibit strong functional overlap and that when one protein component is depleted, the others can compensate for most of the missing activity, demonstrating that mechanisms for the modulation of photosynthetic electron transport are indispensable.

Differential use of two cyclic electron flows around photosystem I for driving CO2-concentration mechanism in C4 photosynthesis.

The results indicate that CEF via NDH plays a central role in driving the CO(2)-concentrating mechanism in C(4) photosynthesis.

Regulation of cyclic electron flow by chloroplast NADPH-dependent thioredoxin system

Linear electron transport in the thylakoid membrane drives both photosynthetic NADPH and ATP production, while cyclic electron flow (CEF) around photosystem I only promotes the translocation of



Concerning a dual function of coupled cyclic electron transport in leaves.

Coupled cyclic electron transport is assigned a role in the protection of leaves against photoinhibition in addition to its role in ATP synthesis and avoidance of overreduction of the electron transport chain is a prerequisite for the efficient protection of the photosynthetic apparatus against photo inactivation.

Cyclic electron transfer in plant leaf

  • P. JoliotA. Joliot
  • Biology
    Proceedings of the National Academy of Sciences of the United States of America
  • 2002
It is proposed that the cyclic pathway operates within a supercomplex including one PSI, one cytochrome bf complex, one plastocyanin, and one ferredoxin, which induces the synthesis of ATP needed for the activation of the Benson–Calvin cycle.

Electron transport and photophosphorylation by Photosystem I in vivo in plants and cyanobacteria

Under high light intensities where CO2 can limit photosynthesis, the proton gradient established by coupled cyclic electron transport can prevent over-reduction of the electron transport system by increasing thermal de-excitation in Photosystem II (Weis and Berry 1987).

Photosynthetic control of chloroplast gene expression

Here it is shown that the redox state of plastoquinone also controls the rate of transcription of genes encoding reaction-centre apoproteins of photosystem I and photosystem II, and the stoichiometry between the two photosystems changes in a way that counteracts the inefficiency produced when either photosystem limits the rates of the other.

Electron acceptors in isolated intact spinach chloroplasts act hierarchically to prevent over-reduction and competition for electrons

The different electron acceptors in the stroma are organized in a hierarchical manner; this allows electron flux towards CO2 and nitrite reduction to proceed without any competition for electrons, and any excess electrons to be taken by these additional non-assimilatory pathways.

Photosynthesis by Isolated Chloroplasts

Evidence is given for the action of the photochemically generated assimilatory power on two phases of the reductive carbohydrate cycle in isolated chloroplasts: the carboxylative phase which includes the phosphorylation of ribulose monophosphate and the fixation of COZ, and the reduction of 3-phosphoglyceric acid and the formation of hexose phosphate.

Irrungen, Wirrungen? The Mehler reaction in relation to cyclic electron transport in C3 plants

  • U. Heber
  • Environmental Science
    Photosynthesis Research
  • 2004
Cyclic electron flow acts in flexible relationship with the water–water cycle to control Photosystem II activity, which relieves the inhibition of cyclic electron transport, which is observed under excessive reduction of intersystem electron carriers.

THE WATER-WATER CYCLE IN CHLOROPLASTS: Scavenging of Active Oxygens and Dissipation of Excess Photons.

  • K. Asada
  • Environmental Science, Engineering
    Annual review of plant physiology and plant molecular biology
  • 1999
Whenever the water-water cycle operates properly for scavenging of active oxygens in chloroplasts, it also effectively dissipates excess excitation energy under environmental stress.

Directed disruption of the tobacco ndhB gene impairs cyclic electron flow around photosystem I.

Analysis of the transient increase in chlorophyll fluorescence after actinic light illumination and the redox kinetics of P700 suggest that the cyclic electron flow around PS I is impaired in the ndhB-deficient transformants, suggesting that the cycling of electrons aroundPS I mediated by ndh gene products is dispensable in tobacco under mild environmental conditions.