Properties of photoreductions by Photosystem II in isolated chloroplasts. An energy-conserving step in the photoreduction of benzoquinones by Photosystem II in the presence of dibromothymoquinone

Trebst, Achim; Reimer, S.

doi:10.1016/0005-2728(73)90238-7

Cited by 89 publications

(20 citation statements)

References 17 publications

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“…The results reported here with trifluralin are reminiscent of effects observed with DBMIB (8,18), most notably the reversal by class III acceptors of the inhibition of ferricyanide reduction. There are, however, differences between DBMIB and trifluralin.…”

Section: Methodssupporting

confidence: 58%

Inhibition of Chloroplast Electron Transport Reactions by Trifluralin and Diallate

et al. 1977

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Section: Methodssupporting

confidence: 58%

Inhibition of Chloroplast Electron Transport Reactions by Trifluralin and Diallate

et al. 1977

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“…This suggests that about 65% of the DMQ reduction was mediated by PSII alone. The concentration of DBMIB required to block the H20 --MV reaction (>3 ,UM) was approximately five times higher than that required in isolated spinach chloroplasts (16,27), indicating that in BS cells the accessibility of the thylakoids to DBMIB is somewhat limited.…”

mentioning

confidence: 88%

Photosynthetic Electron Transport in Isolated Maize Bundle Sheath Cells

Walker¹,

Izawa²

1979

Plant Physiol.

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Fragments of bundle sheath strands, free of mesophyll cells and showing a chlorophyll a/b ratio of 6.0 to 6.6 were prepared from Zea mays by a mechanical method. They were unable to photoreduce ferricyanide but were able to photoreduce the membrane-permeant 2,5-dimethylquinone at a rate of 250 to 420 microequivalents per hour per mg chlorophyll (ueq/hr.mg Chi) at 21 C. In the presence of the catalase inhibitor KCN We have attempted to reevaluate the in situ photochemical activities of chloroplasts in isolated maize BS fragments by carefully optimizing the reaction conditions. We used 2,5-dimethylquinone (DMQ) as the PSII electron acceptor, which is a membranepermeant oxidant and is by far the more stable and therefore more reliable as a PSII acceptor than is unsubstituted p-benzoquinone (24). MV, a standard PSI electron acceptor for chloroplast studies, tumed out to be useful also for isolated BS cells. This was not surprising, since MV is a widely used contact herbicide ("paraquat") and is known to penetrate the leaf tissue readily (see, e.g. 3).The in situ photochemical activities of maize BS chloroplasts are quite comparable to the highest activities reported for isolated BS chloroplasts (9). Perhaps more importantly, this paper also describes experiments in which we have successfully detected an electron transport-dependent H+ uptake by isolated BS fragments. Preparation of BS Fragments. BS fragments were isolated from secondary leaves taken from 2-to 4-week-old plants. All isolation procedures were performed at 0 to 4 C using ice-chilled media. Ten to 12 g (fresh weight) of leaves were cut transversely into Ito 2-cm segments. Two to 3 g of these segments were combined with 5 ml of the isolation medium that contained 0.5 M sucrose, 80 mM Tricine-NaOH buffer (pH 7.8), 5 mM MgCl2, 10 mm KCI, 0.2% BSA, and 0.1% PVP (PVP-40, Sigma). The leaf segments were then thoroughly macerated (4-5 min) using a pair of razor blades attached to an electric kitchen knife. This step removed most of the mesophyll cells and the epidermis from the tissue. The fragments were transferred to a beaker together with the medium and kept in suspension using a magnetic stirrer. The procedure was repeated until the entire 10 to 12 g of the original material was processed. The suspension was then filtered though two layers of Miracloth, and the tissue remaining on the cloth was briefly rinsed with distilled H20. The washed fragments were resuspended in 150 ml of the isolation medium and sheared in a Waring Blendor for 9 to 15 sec in 3-sec bursts at low speed. MATERIALS

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“…, Trebst and associates [6,7] have reported that the benzoquinone derivative, dibromothymoquinone (DBMIB), is a competitive antagonist of PQ and that it is an effective inhibitor of electron transport between the two photoacts. On the basis of investigations with DBMIB, BiShme et al [7] have classified the various cyclic photophosphorylations in vitro and Izawa et al [8] and Trebst and Reimer [9] have * Abbreviations: PMS, methyl-phenazoniummethosulfate; DAD, 2,3,5,6-tetramethyl-p-phenylenediamine; DCPIP, dichlorophenolindophenol; DBMIB, 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone; DCMU, 3(3,4-dichlorophenyl)-1,1-dimethylurea; PQ, plastoquinone.…”

Section: Introductionmentioning

confidence: 99%

The role of plastoquinone in the in vivo photosynthetic cyclic electron transport pathway in algae

Biggins

1974

FEBS Letters

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Properties of photoreductions by Photosystem II in isolated chloroplasts. An energy-conserving step in the photoreduction of benzoquinones by Photosystem II in the presence of dibromothymoquinone

Cited by 89 publications

References 17 publications

Inhibition of Chloroplast Electron Transport Reactions by Trifluralin and Diallate

Inhibition of Chloroplast Electron Transport Reactions by Trifluralin and Diallate

Photosynthetic Electron Transport in Isolated Maize Bundle Sheath Cells

The role of plastoquinone in the in vivo photosynthetic cyclic electron transport pathway in algae

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