Detecting localized proton currents in photophosphorylation by procaine inhibition of the transthylakoid pH-gradient

Laasch, Henrik; Ihle, Carolin; Günther, Gabriele

doi:10.1016/0005-2728(93)90064-m

Cited by 10 publications

(7 citation statements)

References 32 publications

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“…To evaluate the activity of ΔpH generation more quantitatively, we estimated the ΔpH from the quenching of 9‐aminoacridine (9‐AA) fluorescence in isolated thylakoids according to the calculations established by Schuldiner et al . (1972) and Laasch et al . (1993) (Figure 6).…”

Section: Resultsmentioning

confidence: 96%

“…The calculation of the transmembrane ΔpH from the light‐induced 9‐AA fluorescence quenching indicated that ΔpH is about 1 pH unit smaller in pgr1 than in the wild type. It should be noted, however, that our calculations represent only rough estimations based on empirical data obtained with spinach thylakoids (Laasch et al ., 1993; Schuldiner et al ., 1972), which are not necessarily applicable to Arabidopsis thylakoid preparations. However, we confirmed the reliability of the response of the indicating dye 9‐AA by varying the external pH.…”

Section: Discussionmentioning

confidence: 99%

“…The maximum ΔpH was calculated from the quenching of 9‐AA fluorescence under illumination with saturating actinic red light (λ > 630 nm) following the approach Schuldiner et al . (1972) and applying the calculations Laasch et al . (1993).…”

Section: Methodsmentioning

confidence: 99%

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Cytochrome b₆f mutation specifically affects thermal dissipation of absorbed light energy in Arabidopsis

et al. 2001

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SummaryLight-induced lumenal acidi®cation controls the ef®ciency of light harvesting by inducing thermal dissipation of excess absorbed light energy in photosystem II. We isolated an Arabidopsis mutant, pgr1 (proton gradient regulation), entirely lacking thermal dissipation, which was observed as little nonphotochemical quenching of chlorophyll¯uorescence. Map-based cloning showed that pgr1 had a point mutation in petC encoding the Rieske subunit of the cytochrome b 6 f complex. Although the electron transport rate was not affected at low light intensity, it was signi®cantly restricted at high light intensity in pgr1, indicating that the lumenal acidi®cation was not suf®cient to induce thermal dissipation. This view was supported by (i) slow de-epoxidation of violaXanthin, which is closely related to lumenal acidi®cation, and (ii) reduced 9-aminoacridine¯uorescence quenching. Although lumenal acidi®cation was insuf®cient to induce thermal dissipation, growth rate was not affected under low light growth conditions in pgr1. These results suggest that thermal dissipation is precisely regulated by lumenal pH to maintain maximum photosynthetic activity. We showed that pgr1 was sensitive to changes in light conditions, demonstrating that maximum activity of the cytochrome b 6 f complex is indispensable for short-term acclimation.

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Section: Resultsmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

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Cytochrome b₆f mutation specifically affects thermal dissipation of absorbed light energy in Arabidopsis

et al. 2001

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“…The maximum ΔpH was calculated from the quenching of 9‐AA fluorescence under illumination with saturating actinic red light ( λ >630 nm) following the approach by Schuldiner et al [20] and applying the calculations from Laasch et al [21].…”

Section: Methodsmentioning

confidence: 99%

Single point mutation in the Rieske iron–sulfur subunit of cytochrome b₆/f leads to an altered pH dependence of plastoquinol oxidation in Arabidopsis

et al. 2002

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The pgr1 mutant of Arabidopsis thaliana carries a single point mutation (P194L) in the Rieske subunit of the cytochrome b 6 /f (cyt b 6 /f) complex and is characterised by a reduced electron transport activity at saturating light intensities in vivo. We have investigated the electron transport in this mutant under in vitro conditions. Measurements of P700 reduction kinetics and of photosynthetic electron transport rates indicated that electron transfer from cyt b 6 /f to photosystem I is not generally reduced in the mutant, but that the pH dependence of this reaction is altered. The data imply that the pH-dependent inactivation of electron transport through cyt b 6 /f is shifted by about 1 pH unit to more alkaline pH values in pgr1 thylakoids in comparison with wild-type thylakoids. This interpretation was confirmed by determination of the transmembrane v vpH at different stromal pH values showing that the lumen pH in pgr1 mutant plants cannot drop below pH 6 reflecting most likely a shift of the pK and/or the redox potential of the oxidised Rieske protein. ß

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“…After reaching the maximum DpH, 0.1 mM ADP was added to test the functionality of ATP synthesis. The DpH was calculated from the quenching of 9-AA fluorescence following the approach by Schuldiner et al (1972) and applying the calculations from Laasch et al (1993).…”

Section: Measurement Of 9-aminoacridine Fluorescencementioning

confidence: 99%

Characterization of a nonphotochemical quenching-deficient Arabidopsis mutant possessing an intact PsbS protein, xanthophyll cycle and lumen acidification

Kalituho

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Graf

et al. 2005

Planta

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Arabidopsis thaliana plants grown from ethyl methane sulfonate-treated seeds were screened for so-called que mutants, which are affected in non-photochemical energy quenching. Based on video imaging of chlorophyll fluorescence an energy dissipation mutant, que1, was identified, isolated and characterized. Similar to the npq mutants, the que1 mutant showed a drastically reduced capacity for pH-dependent energy dissipation, qE, but without affecting the Delta pH-dependent conformational changes at 535 nm (DeltaA (535)), which have been supposed to be obligatorily correlated with qE and to reflect pH-regulated binding of zeaxanthin to the PsbS protein. Western blot and DNA sequence analysis revealed that neither a reduced expression of the PsbS protein nor a mutation in the PsbS gene was responsible for the missing qE in que1. Measurements of 9-aminoacridine fluorescence quenching showed that the acidification of the thylakoid lumen was also not affected in the mutant. Furthermore, que1 was able to convert violaxanthin to zeaxanthin. However, unusual characteristics of zeaxanthin formation in the mutant pointed at an altered availability of violaxanthin for de-epoxidation. This was further accompanied by a decrease of the photochemical quenching of chlorophyll fluorescence (qP), an increase of the portion of oxidized P700 and a reduction of the electron transport rate. These characteristics indicate changes in the organization of the thylakoid membrane that affect linear electron transport (but not lumen acidification) and the formation of energy dissipation in photosystem II. Preliminary genetic analysis revealed that the phenotype of que1 is related to two different mutations, mapped to the lower arms of chromosomes 1 and 4.

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Detecting localized proton currents in photophosphorylation by procaine inhibition of the transthylakoid pH-gradient

Cited by 10 publications

References 32 publications

Cytochrome b₆f mutation specifically affects thermal dissipation of absorbed light energy in Arabidopsis

Cytochrome b₆f mutation specifically affects thermal dissipation of absorbed light energy in Arabidopsis

Single point mutation in the Rieske iron–sulfur subunit of cytochrome b₆/f leads to an altered pH dependence of plastoquinol oxidation in Arabidopsis

Characterization of a nonphotochemical quenching-deficient Arabidopsis mutant possessing an intact PsbS protein, xanthophyll cycle and lumen acidification

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Detecting localized proton currents in photophosphorylation by procaine inhibition of the transthylakoid pH-gradient

Cited by 10 publications

References 32 publications

Cytochrome b6f mutation specifically affects thermal dissipation of absorbed light energy in Arabidopsis

Cytochrome b6f mutation specifically affects thermal dissipation of absorbed light energy in Arabidopsis

Single point mutation in the Rieske iron–sulfur subunit of cytochrome b6/f leads to an altered pH dependence of plastoquinol oxidation in Arabidopsis

Characterization of a nonphotochemical quenching-deficient Arabidopsis mutant possessing an intact PsbS protein, xanthophyll cycle and lumen acidification

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Cytochrome b₆f mutation specifically affects thermal dissipation of absorbed light energy in Arabidopsis

Cytochrome b₆f mutation specifically affects thermal dissipation of absorbed light energy in Arabidopsis

Single point mutation in the Rieske iron–sulfur subunit of cytochrome b₆/f leads to an altered pH dependence of plastoquinol oxidation in Arabidopsis