Relationship between photosynthetic electron transport and pH gradient across the thylakoid membrane in intact leaves.

Schönknecht, Gerald; Neimanis, Spidola; Katona, Eva; Gerst, Ulvi; Heber, U.

doi:10.1073/pnas.92.26.12185

Cited by 34 publications

(21 citation statements)

References 17 publications

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“…In the light, a relatively high proton gradient occurs across the thylakoid membrane, and in the dark, this difference in pH between cytosol and thylakoid lumen is decreased (49,50). The transition between these two states is achieved by proton diffusion across the thylakoid membrane, which is accompanied by a counter movement of cations to balance both osmolarity and electrochemical gradient.…”

Section: Discussionmentioning

confidence: 99%

Identification and Characterization of the Na+/H+ Antiporter NhaS3 from the Thylakoid Membrane of Synechocystis sp. PCC 6803

Tsunekawa

Shijuku

Hayashimoto

et al. 2009

Journal of Biological Chemistry

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Na؉ /H ؉ antiporters influence proton or sodium motive force across the membrane. Synechocystis sp. PCC 6803 has six genes encoding Na ؉ /H؉ antiporters, nhaS1-5 and sll0556. In this study, the function of NhaS3 was examined. NhaS3 was essential for growth of Synechocystis, and loss of nhaS3 was not complemented by expression of the Escherichia coli Na ؉ /H ؉ antiporter NhaA. Membrane fractionation followed by immunoblotting as well as immunogold labeling revealed that NhaS3 was localized in the thylakoid membrane of Synechocystis. NhaS3 was shown to be functional over a pH range from pH 6.5 to 9.0 when expressed in E. coli. A reduction in the copy number of nhaS3 in the Synechocystis genome rendered the cells more sensitive to high Na ؉ concentrations. NhaS3 had no K ؉ /H ؉ exchange activity itself but enhanced K ؉ uptake from the medium when expressed in an E. coli potassium uptake mutant. Expression of nhaS3 increased after shifting from low CO 2 to high CO 2 conditions. Expression of nhaS3 was also found to be controlled by the circadian rhythm. Gene expression peaked at the beginning of subjective night. This coincided with the time of the lowest rate of CO 2 consumption caused by the ceasing of O 2 -evolving photosynthesis. This is the first report of a Na

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Section: Discussionmentioning

confidence: 99%

Identification and Characterization of the Na+/H+ Antiporter NhaS3 from the Thylakoid Membrane of Synechocystis sp. PCC 6803

Tsunekawa

Shijuku

Hayashimoto

et al. 2009

Journal of Biological Chemistry

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“…In hydrated systems, photoprotective quenching of chlorophyll¯uorescence depends on the formation of a suciently large DpH across the thylakoids which activates zeaxanthin formation (PfuÈ ndel et al 1994;SchoÈ nknecht et al 1995;Horton et al 1996;Owens 1996;Gilmore and Govindjee 1999). Carbon assimilation is unlikely to provide for such a proton gradient because ATP synthesis during electron transport to CO 2 consumes, at H + /e = 3 and H + /ATP = 4 (Rumberg et al 1990;Rich 1991;Kobayashi et al 1995), as many protons as are deposited inside the thylakoids during electron transport to CO 2 .…”

Section: Cyclic Electron Transport As a Source Of Npqmentioning

confidence: 99%

Phototolerance of lichens, mosses and higher plants in an alpine environment: analysis of photoreactions

Heber

Bilger²,

Bligny

et al. 2000

Planta

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Adaptation to excessive light is one of the requirements of survival in an alpine environment particularly for poikilohydric organisms which in contrast to the leaves of higher plants tolerate full dehydration. Changes in modulated chlorophyll fluorescence and 820-nm absorption were investigated in the lichens Xanthoria elegans (Link) Th. Fr. and Rhizocarpon geographicum (L.) DC, in the moss Grimmia alpestris Limpr. and the higher plants Geum montanum L., Gentiana lutea L. and Pisum sativum L., all collected at altitudes higher than 2000 m above sea level. In the dehydrated state, chlorophyll fluorescence was very low in the lichens and the moss, but high in the higher plants. It increased on rehydration in the lichens and the moss, but decreased in the higher plants. Light-induced charge separation in photosystem II was indicated by pulse-induced fluorescence increases only in dried leaves, not in the dry moss and dry lichens. Strong illumination caused photodamage in the dried leaves, but not in the dry moss and dry lichens. Light-dependent increases in 820-nm absorption revealed formation of potential quenchers of chlorophyll fluorescence in all dehydrated plants, but energy transfer to quenchers decreased chlorophyll fluorescence only in the moss and the lichens, not in the higher plants. In hydrated systems, coupled cyclic electron transport is suggested to occur concurrently with linear electron transport under strong actinic illumination particularly in the lichens because far more electrons became available after actinic illumination for the reduction of photo-oxidized P700 than were available in the pool of electron carriers between photosystems II and I. In the moss Grimmia, but not in the lichens or in leaves, light-dependent quenching of chlorophyll fluorescence was extensive even under nitrogen, indicating anaerobic thylakoid acidification by persistent cyclic electron transport. In the absence of actinic illumination, acidification by ca. 8% CO2 in air quenched the initial chlorophyll fluorescence yield Fo only in the hydrated moss and the lichens, not in leaves of the higher plants. Under the same conditions, 8% CO2 reduced the maximal fluorescence yield Fm strongly in the poikilohydric organisms, but only weakly or not at all in leaves. The data indicate the existence of deactivation pathways which enable poikilohydric organisms to avoid photodamage not only in the hydrated but also in the dehydrated state. In the hydrated state, strong nonphotochemical quenching of chlorophyll fluorescence indicated highly sensitive responses to excess light which facilitated the harmless dissipation of absorbed excitation energy into heat. Protonation-dependent fluorescence quenching by cyclic electron transport, P700 oxidation and, possibly, excitation transfer between the photosystems were effectively combined to produce phototolerance.

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“…We thus estimate relative g H ϩ as the reciprocal of the ECS decay time constant, (1͞ ECS ), as described in ref. 60. Fig.…”

Section: The Effects Of Light and Co2 Levels On The Conductivity Of Tmentioning

confidence: 99%

“…60). Because proton flux is expected to be proportional to LEF (31), we plotted NPQ against LEF͞g H ϩ (Fig.…”

Section: Changes In G Hmentioning

confidence: 99%

In vivo modulation of nonphotochemical exciton quenching (NPQ) by regulation of the chloroplast ATP synthase

Kanazawa

Kramer

2002

Proc. Natl. Acad. Sci. U.S.A.

326

318

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Nonphotochemical quenching (NPQ) of excitation energy, which protects higher plant photosynthetic machinery from photodamage, is triggered by acidification of the thylakoid lumen as a result of light-induced proton pumping, which also drives the synthesis of ATP. It is clear that the sensitivity of NPQ is modulated in response to changing physiological conditions, but the mechanism for this modulation has remained unclear. Evidence is presented that, in intact tobacco or Arabidopsis leaves, NPQ modulation in response to changing CO 2 levels occurs predominantly by alterations in the conductivity of the CF O-CF1 ATP synthase to protons (g H ؉ ). At a given proton flux, decreasing g H ؉ will increase transthylakoid proton motive force (pmf ), thus lowering lumen pH and contributing to the activation of NPQ. violaxanthin deepoxidase ͉ photoinhibition ͉ xanthophyll cycle ͉ proton motive force ͉ chemiosmotic coupling L ight-driven transthylakoid proton motive force (pmf ) serves two essential roles in higher plant photosynthesis (1). First, it is the central intermediate in the chemiosmotic circuit for light-driven ATP synthesis. Light-driven electron transfer leads to the pumping of protons from the stroma to the thylakoid lumen, establishing pmf, which drives the endergonic synthesis of ATP from ADP and orthophosphate (P i ) at the CF O -CF 1 ATP synthase (ATP synthase).Second, the ⌬pH component of pmf is the key regulatory signal for initiation of nonphotochemical quenching (NPQ) of excitation energy, which is important for photoprotection. Light absorption by the light-harvesting complexes (LHCs) in excess of that which can be processed can lead to harmful side reactions, collectively termed photoinhibition, that can occur at several levels, including the antenna complexes, the oxidizing and reducing sides of photosystem II (PS II), and the reducing side of photosystem I (PS I) (see reviews in refs. 2 and 3).In higher plants, photoinhibition is avoided in part by activation of NPQ, which can dump a large fraction of excitation energy, preventing the accumulation of reactive intermediates (see reviews in refs. 4 and 5-7). It is now generally accepted that NPQ involves two processes activated by acidification of the lumen, the interconversion of xanthophyll cycle carotenoids by violaxanthin deepoxidase (VDE), and the protonation of residues on key LHC components, in particular the psbS subunit (reviewed in ref. 7). Arabidopsis mutants deficient in NPQ are light sensitive, confirming its role in photoprotection (e.g., refs. 8 and 9-12).In the most basic working model for NPQ function (e.g., figure 2 of reference 12), where the kinetic and thermodynamic properties of each step in the process are consistent, NPQ should be a continuous function of linear electron flow (LEF). On the other hand, it has become clear that the relationship between LEF and NPQ is strongly modulated in response to rapid changes in physiological state, and we provide a direct demonstration of this below. It has been suggested that such NPQ mod...

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Relationship between photosynthetic electron transport and pH gradient across the thylakoid membrane in intact leaves.

Cited by 34 publications

References 17 publications

Identification and Characterization of the Na+/H+ Antiporter NhaS3 from the Thylakoid Membrane of Synechocystis sp. PCC 6803

Identification and Characterization of the Na+/H+ Antiporter NhaS3 from the Thylakoid Membrane of Synechocystis sp. PCC 6803

Phototolerance of lichens, mosses and higher plants in an alpine environment: analysis of photoreactions

In vivo modulation of nonphotochemical exciton quenching (NPQ) by regulation of the chloroplast ATP synthase

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