Proton gradients as possible intermediary energy transducers during ATP‐driven reverse electron flow in chloroplasts

Avron, Mordhay; Schreiber, Ulrich

doi:10.1016/0014-5793(77)80180-4

Cited by 32 publications

(13 citation statements)

References 16 publications

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“…Results and discussion Figure 1 illustrates the procedure which was found optimal for high yields of ATP-induced luminescence. The chloroplast suspension was first illuminated with strong, heat-filtered white light for 3 min to activate the latent ATPase [10,12]. From about 5 s after the activating light was turned off, the decay of postillumination luminescence was monitored for 90 s, by which time it approached zero.…”

Section: Methodsmentioning

confidence: 99%

ATP‐induced chlorophyll luminescence in isolated spinach chloroplasts

Schreiber

Avron

1977

FEBS Letters

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Section: Methodsmentioning

confidence: 99%

ATP‐induced chlorophyll luminescence in isolated spinach chloroplasts

Schreiber

Avron

1977

FEBS Letters

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“…Hence it has not been determined whether light has a role other than generation of the ApH required for NPQ and zeaxanthin formation. ATP hydrolysis can generate a ApH (28,29) and with ascorbate present can induce zeaxanthin formation in the dark (5). Whether ATP hydrolysis can similarly induce NPQ in the dark has not been reported.…”

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confidence: 99%

Dark induction of zeaxanthin-dependent nonphotochemical fluorescence quenching mediated by ATP.

Gilmore

Yamamoto

1992

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

163

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Zeaxanthin-dependent nonphotochemical fluorescence quenching is a light-induced activity in plants that apparently protects against the potentially damaging effects of excess light. We report a dark-induced nonphotochemical quenching in thylakoids of Lactuca satva L. cv. Romaine mediated by ATP. This effect is due to low lumen pH from hydrolysis-dependent proton pumping and hence required an active ATPase. The induction was optimal at 0.3 mM ATP, a physiological concentration, and occurred under conditions of little or no reverse electron flow. The properties of ATPinduced quenching were in all respects examined similar to light-induced quenching, including antimycin inhibition of quenching induction but not ApH. We conclude that zeaxanthin-dependent quenching depends directly on lumen pH and that the role of light is indirect. Although it is known that zeaxanthin and low lumen pH are insufficient for quenching to occur, the results apparently exclude the redox state of an electron-transport carrier or formation of light-induced carotenoid triplets as a further requirement. We propose that a slow pH-dependent conformational change together with zeaxanthin cause static quenching in the pigment bed; possibly antimycin inhibits this change. Furthermore, we suggest from the ability of ATP to sustain quenching in the dark for extended periods that persistent or slowly reversible zeaxanthin quenching often observed in vivo may be due to sustained ApH from ATP hydrolysis.High light intensity induces reversible changes in the level of violaxanthin in leaves via the so-called xanthophyll cycle (1-3). Zeaxanthin, which is formed in this cycle from violaxanthin (4) under low lumen pH (5), enhances nonradiative dissipation of excess absorbed energy and thus apparently serves the important function of protecting the photosystem against the potentially damaging effects of excess light (6). In vitro, the rate and extent of zeaxanthin formation are functions of lumen pH, ascorbate concentration, and violaxanthin availability (2). In vivo, zeaxanthin forms when photosynthesis becomes limiting (4,7,8), at high temperature (7, 9), or under other combined stresses (10). Zeaxanthin-forming capacity, thus protective capacity, varies with species and growth history. Plants that are well adapted to high light intensity have larger total pools of xanthophyll-cycle pigments (violaxanthin plus antheraxanthin plus zeaxanthin) than the same species grown under reduced light intensity (11).Nonradiative energy dissipation at photosystem II (PSII) is reflected in nonphotochemical quenching (NPQ) of roomtemperature fluorescence (12-15). The correlation of NPQ with zeaxanthin formation, first reported by Demmig et al. (16) in leaves, has since been observed in intact chloroplasts (17) and thylakoids (18). Zeaxanthin-dependent NPQ is of the "high-energy" or ApH-dependent type (17-19) as is zeaxanthin-independent or constitutive NPQ that is also present in many systems (17)(18)(19)(20). Lowering of the intrinsic quantum efficiency or "do...

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“…4 The formation of a light-induced ApH was monitored by observing changes in fluorescence of 9-AA3 (25). The experimental apparatus was described by Avron and Schreiber (1). Four hundred Il cell suspension or cell-free preparation were introduced into the instrumental chamber in the dark.…”

Section: Methodsmentioning

confidence: 99%

“…Addition of inhibitors or changes of NaCl concentration were made by injecting into the chamber using the connected syringe. Sources of light and the method used to determine 9-AA fluorescence yield were those described in detail by Avron and Schreiber (1). Data are presented on the basis of relative changes in fluorescence intensity.…”

Section: Methodsmentioning

confidence: 99%

Light-Induced Proton Gradient Formation in Intact Cells of Dunaliella salina

Schreiber¹

1981

Plant Physiol.

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A light-induced proton gradient (ApH) increase as exhibited by an increase of 9-aminoacridine fluorescence quenching is demonstrated between the external medium and the interior of the halophytic green alga Dwaiella saUna. The A light-induced proton uptake has been reported in Dunaliella (2). This proton uptake has been attributed to the activity of an Na+/H+ exchange mechanism which may be related to the maintenance of the Na+ concentration gradient between the cells and the surrounding medium (18). Neumann and Levine (20), on the other hand, suggested that the uptake of protons in the light is the result of CO2 uptake in photosynthesis. In the study reported here we confirm a light-induced proton uptake in intact Dunaliella cells. The response of the ApH to electron transport and ATPase inhibitors, to sulfhydryl reagent as well as to the Na+ concentration in the medium are reported. The data suggest that an (Na+/H+)-ATPase localized in the cell membrane may be involved in the uptake of protons in the light. MATERIALS AND METHODSDunaliella salina cells were grown as described previously (15,16). Cells were harvested by centrifugation at room temperature at 700g for 5 min and washed twice in growth medium in which the Tris buffer was replaced by 50 mm Hepes buffer (pH 7.5). Cell-free preparations were obtained by the addition of cold (2 C) distilled H20 to the cell suspension to yield final NaCl concentration of 0.2 M. This treatment resulted in a complete rupture of the cells. The cell-free suspension was then centrifuged (lO,000g, 10 min, 4 C) and resuspended in a medium containing 0.4 M sucrose and 5 mM MgCl2 in 50 mm Hepes buffer (pH 7.8).

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Proton gradients as possible intermediary energy transducers during ATP‐driven reverse electron flow in chloroplasts

Cited by 32 publications

References 16 publications

ATP‐induced chlorophyll luminescence in isolated spinach chloroplasts

ATP‐induced chlorophyll luminescence in isolated spinach chloroplasts

Dark induction of zeaxanthin-dependent nonphotochemical fluorescence quenching mediated by ATP.

Light-Induced Proton Gradient Formation in Intact Cells of Dunaliella salina

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