The Dynamics of Photosynthesis

Eberhard, Stephan; Finazzi, Guido; Wollman, Françis-André

doi:10.1146/annurev.genet.42.110807.091452

Cited by 602 publications

(467 citation statements)

References 337 publications

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“…Although many components are involved, for simplicity, changes in the redox status are symbolized by the over-reduction of the NADP pool (vertical red arrows) owing to either decreased NADPH consumption in nutrient-deprived Chlamydomonas or excess of excitation energy (owing to a higher surface/volume ratio) in Volvox somatic cells. The switch to cyclic electron transport (CET), which can maintain ATP synthesis (and thus vital processes) in acclimated Chlamydomonas cells (Eberhard et al 2008) and possibly in Volvox somatic cells, is also indicated.…”

Section: Discussionmentioning

confidence: 99%

Environmentally induced responses co-opted for reproductive altruism

Nedelcu

2009

Biol. Lett.

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Reproductive altruism is an extreme form of altruism best typified by sterile castes in social insects and somatic cells in multicellular organisms. Although reproductive altruism is central to the evolution of multicellularity and eusociality, the mechanistic basis for the evolution of this behaviour is yet to be deciphered. Here, we report that the gene responsible for the permanent suppression of reproduction in the somatic cells of the multicellular green alga, Volvox carteri , evolved from a gene that in its unicellular relative, Chlamydomonas reinhardtii , is part of the general acclimation response to various environmental stress factors, which includes the temporary suppression of reproduction. Furthermore, we propose a model for the evolution of soma, in which by simulating the acclimation signal (i.e. a change in cellular redox status) in a developmental rather than environmental context, responses beneficial to a unicellular individual can be co-opted into an altruistic behaviour at the group level. The co-option of environmentally induced responses for reproductive altruism can contribute to the stability of this behaviour, as the loss of such responses would be costly for the individual. This hypothesis also predicts that temporally varying environments, which will select for more efficient acclimation responses, are likely to be more conducive to the evolution of reproductive altruism.

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Section: Discussionmentioning

confidence: 99%

Environmentally induced responses co-opted for reproductive altruism

Nedelcu

2009

Biol. Lett.

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“…The energy-storing processes of photosynthesis start with the capture of photosynthetically active radiation (PAR) by photoactive pigments, transfer of the energy to specialized chlorophyll molecules in photosystems I (PSI) and II (PSII), inducing the transfer of electrons through a series of redox intermediates to ultimately generate NADPH from NADP + (7). The electron transfer steps are tightly coupled to proton transfer reactions into the thylakoid lumen, storing potential energy in the pmf to drive the synthesis of ATP (8,9).…”

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confidence: 99%

Hacking the thylakoid proton motive force for improved photosynthesis: modulating ion flux rates that control proton motive force partitioning into Δ ψ and ΔpH

Davis

Rutherford

Kramer

2017

Phil. Trans. R. Soc. B

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SummaryThere is considerable interest in improving plant productivity by altering the dynamic responses of photosynthesis in tune with natural conditions. This is exemplified by the "energy-dependent" form of nonphotochemical quenching (q E ), the formation and decay of which can be considerably slower than natural light fluctuations, limiting photochemical yield. In addition, we recently reported that rapidly fluctuating light can produce Field Recombination Induced Photodamage (FRIP), where large spikes in electric field across the thylakoid membrane (Δψ) induce photosystem II recombination reactions that produce damaging singlet oxygen ( 1 O 2 ). Both q E and FRIP are directly linked to the thylakoid proton motive force (pmf), and in particular the slow kinetics of partitioning pmf into its ΔpH and Δψ components. Using a series of computational simulations, we explored the possibility of "hacking" pmf partitioning as a target for improving photosynthesis. Under a range of illumination conditions, increasing the rate of counter-ion fluxes across the thylakoid membrane should lead to more rapid dissipation of Δψ and formation of ΔpH. This would result in increased rates for the formation and decay of q E while ameliorating the amplitudes of Δψ-spikes and decreasing 1 O 2 production. These results suggest that ion fluxes may be a viable target for plant breeding or engineering. However, these changes also induce transient, but substantial mismatches in the ATP:NADPH output ratio as well as in the osmotic balance between the lumen and stroma, either of which may explain why evolution has not already accelerated thylakoid ion fluxes. Overall, though the model is simplified, it recapitulates many of the responses seen in vivo, while spotlighting critical aspects of the complex interactions between pmf components and photosynthetic processes. By making the program available, we hope to enable the community of photosynthesis researchers to further explore and test specific hypotheses.*Author for correspondence (kramerd8@cns.msu.edu). 2This opinion/hypothesis paper was inspired by the recent Royal Society symposium on "Enhancing Photosynthesis in Crop Plants: Targets for Improvement," (http://www.rsc.org/events/download/Document/cee7d4f2-9ff1-477b-b155-3e2492577d77) that brought together experts in a range of photosynthetic processes. A prominent theme of several of the presentations was the sensitivity of photosynthesis to rapid, rather than gradual, changes in environmental conditions. Of particular interest was the kinetic mismatch between fluctuations in photosynthetically active radiation (PAR), which can change by orders of magnitude within a second, and the relatively slow onset of photoprotective mechanisms (1, 2). Indeed, there is growing evidence that this mismatch can sensitize both PSI and PSII to oxidative photodamage (3, 4), of which the focus of this paper is the irreversible damage to PSII (to D1 and other subunits) due to 1 O 2 generated by PSII charge recombination. It has also been proposed that the...

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“…Hence the biogenesis of the photosynthetic apparatus involves a concerted interplay between the chloroplast and nucleocytosolic genetic systems as well as a tight coordination between protein and pigment synthesis and insertion into the thylakoid membranes. Analysis of numerous mutants affected in photosynthetic activity in Chlamydomonas reinhardtii, Arabidopsis (Arabidopsis thaliana), and Zea mays has provided many new insights into the assembly of the photosynthetic complexes (Barkan and Goldschmidt-Clermont, 2000;Eberhard et al, 2008).A remarkable feature of photosynthetic organisms is their ability to adapt to changing light conditions, which is reflected in changes in the organization of the photosynthetic complexes. This Update reviews recent advances in our understanding of the assembly of these complexes and for some of them, their remodeling and/or reversible association into supercomplexes that depends on environmental conditions.…”

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confidence: 99%

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confidence: 99%

Assembly of the Photosynthetic Apparatus

Rochaix

2011

Plant Physiology

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The primary reactions of photosynthesis are mediated by three protein complexes embedded in the thylakoid membranes of chloroplasts. These complexes are PSII, the cytochrome b 6 f complex (Cytb 6 f), and PSI, which are connected in series through the photosynthetic electron transport chain. Light energy captured by the light-harvesting systems of PSII (LHCII) and PSI (LHCI) is transferred to the reaction center chlorophylls to create a charge separation across the membrane. This leads to the formation of a strong oxidant on the donor side of PSII capable of splitting water into molecular oxygen, protons, and electrons. The electrons are transferred stepwise from PSII to the plastoquinone pool, Cytb 6 f, plastocyanin, and PSI where a second charge separation creates a strong reductant capable of reducing ferredoxin that subsequently reduces NADP + to NADPH. Besides this linear electron pathway there is a cyclic pathway in which electrons are cycled around PSI through the Cytb 6 f complex. The electron transfer reactions are coupled to proton pumping into the lumen space of the thylakoids and the resulting pH gradient drives the ATP synthase for ATP production. Ultimately NADPH and ATP are used for CO 2 assimilation by the Calvin-Benson cycle. Thylakoid membranes of land plants are organized in two domains, the grana stacks, comprising 80% of the membrane, and the stromal nonappressed membranes that connect different grana stacks. The photosynthetic complexes with exception of Cytb 6 f, are not distributed evenly through the thylakoid membrane system. Whereas PSII is mostly confined to the grana regions, PSI and ATP synthase are located in the stroma lamellae. Electron transfer between these complexes is mediated by the diffusible electron carriers plastoquinone and plastocyanin.A characteristic feature of the photosynthetic complexes is that they all consist of numerous chloroplast and nucleus-encoded subunits. In the case of PSII, PSI, and Cytb 6 f these complexes contain in addition pigments such as chlorophylls and xanthophylls as well as hemes, quinones, and iron-sulfur (Fe-S) centers that act as redox cofactors. Hence the biogenesis of the photosynthetic apparatus involves a concerted interplay between the chloroplast and nucleocytosolic genetic systems as well as a tight coordination between protein and pigment synthesis and insertion into the thylakoid membranes. Analysis of numerous mutants affected in photosynthetic activity in Chlamydomonas reinhardtii, Arabidopsis (Arabidopsis thaliana), and Zea mays has provided many new insights into the assembly of the photosynthetic complexes (Barkan and Goldschmidt-Clermont, 2000;Eberhard et al., 2008).A remarkable feature of photosynthetic organisms is their ability to adapt to changing light conditions, which is reflected in changes in the organization of the photosynthetic complexes. This Update reviews recent advances in our understanding of the assembly of these complexes and for some of them, their remodeling and/or reversible association into supercomplexes...

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The Dynamics of Photosynthesis

Cited by 602 publications

References 337 publications

Environmentally induced responses co-opted for reproductive altruism

Environmentally induced responses co-opted for reproductive altruism

Hacking the thylakoid proton motive force for improved photosynthesis: modulating ion flux rates that control proton motive force partitioning into Δ ψ and ΔpH

Assembly of the Photosynthetic Apparatus

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