Net Proton Transport in Sunflower Hypocotyls: Comparative Studies of Inhibitors

Böttger, Michael; Bigdon, Michael; Soll, Hans-Jürgen

doi:10.1016/s0044-328x(84)80066-5

Cited by 9 publications

(3 citation statements)

References 21 publications

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“…H+ secretion was at least partially restored after about 2 h (data not shown). This recovery and a following overcompensation is typical and often seen after inhibitor treatments (8). The as we are using a system with high time resolution.…”

Section: Methodsmentioning

confidence: 76%

Hormone Action on Transmembrane Electron and H⁺ Transport

Böttger¹,

Hilgendorf²

1988

Plant Physiol.

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A possible involvement of two different systems in proton translocation was investigated by simultaneous measurement of transmembrane electron flow and proton secretion in a pH-stat combined with a redoxstat. The pH gradient between cytoplasm and apoplast is probably maintained by an H+-pumping ATPase and by a second proton extrusion system, which seems to be linked to a redox chain with NAD(P)H as electron donor. Indole acetic acid inhibits both e-and H+ efflux, but only if the 'electron draw' from the outside is not too high. The electron draw depends on the hexacyanoferrate level at the plasmalemma surface and on the Ca2+ concentration. The inhibiting effect of auxin on e-and H+ efux in the presence of hexacyanoferrate can be only detected at low levels of bivalent cations and of the artificial electron acceptor. The inhibition of e-and H+ efflux by auxin requires high oxygen levels. idants like HCF III or HCI IV will very likely impair the functions of a variety of plasmalemma proteins, including channels, cotransporters, pumps, and auxin-receptors by oxidizing sulfhydryl groups of the proteins (6). In other words, a number of important transport functions may be impaired which would alter electron and/or proton movement. (c) Alcohols can be used to increase the level of intracellular NADH through the action of the cytoplasmic alcohol dehydrogenase (6, 10, 11). Alcohols, known to be substrates for alcohol dehydrogenase such as propan-1-ol, ethanol, and butan-1-ol increase net H+ efflux immediately; propan-2-ol and methanol have no effect. This stereoselectivity and the requirement of high 02 supply for alcohol action exclude an explanation as a membrane effect. Exogenous NADH was found to increase HCF III reduction of protoplasts (21) and of intact roots (29). Komor et al. (20) have demonstrated that reduction of externally applied NAD(P)H with concomitant acidificaton in the apoplast is without involvement of transmembrane steps. An independence of transplasma membrane proton gradient from NAD(P)H-HCF III oxidoredtction in maize root microsoms was described (24). We therefore avoided addition of NAD(P)H and tried to distinguish between H+-pumping ATPase and redoxchain-linked proton extrusion by the use of different 02 pressures as the ATP generating system and the plasmalemma NAD(P)H oxidase have very different Km values for 02.The aim of the present paper is to investigate the influence of hormones and other effectors on the proton extrusion and its possible linkage to transmembrane electron transfer. MATERIALS AND METHODS

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Section: Methodsmentioning

confidence: 76%

Hormone Action on Transmembrane Electron and H⁺ Transport

Böttger¹,

Hilgendorf²

1988

Plant Physiol.

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“…For example, if intracellular H+ transport were sensitive to protein synthesis inhibitors but H+ extrusion through the plasma membrane were not, the suggested difference in subcellular distribution between FC-and auxin-induced H+ transport processes would account for the heretofore unexplained fact that protein synthesis inhibitors completely block auxinstimulated H+ extrusion, but inhibit optimally FC-induced H+ export only marginally (references cited in 35). Also, if intracellular H+ pumping, which can lead to H+ extrusion only after the time required for vesicle transport and exocytosis, were sensitive to lower FC concentrations than plasma membrane transport, this would explain why low FC concentrations stimulate H+ extrusion only after a time lag similar to that for IAA stimulation, whereas higher FC concentrations stimulate almost immediately (6,35). It could also explain why H+ extrusion may be more sensitive to protein synthesis inhibitors at low than at high FC concentrations (6).…”

mentioning

confidence: 99%

“…Also, if intracellular H+ pumping, which can lead to H+ extrusion only after the time required for vesicle transport and exocytosis, were sensitive to lower FC concentrations than plasma membrane transport, this would explain why low FC concentrations stimulate H+ extrusion only after a time lag similar to that for IAA stimulation, whereas higher FC concentrations stimulate almost immediately (6,35). It could also explain why H+ extrusion may be more sensitive to protein synthesis inhibitors at low than at high FC concentrations (6).…”

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confidence: 99%

Auxin and Fusicoccin Enhancement of β-Glucan Synthase in Peas

Ray¹

1985

Plant Physiol.

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Fusicoccin (FC), like indoleacetic acid (IAA), causes Golgi-localized B-1,4-glucan synthase (GS) activity to increase when applied to pea third internode segments whose GS activity has declined after isolation from the plant. This suggests that GS activity is modulated by H' extrusion; in agreement, vanadate and nigericin inhibit the GS response. The GS response is not due to acidification of the cell wall. Treatment of tissue with heavy water, which in effect raises intracellular pH, mimics the MATERIALS AND METHODS Pea (Pisum sativum cv Alaska) seedlings were grown and third internode segments 8 mm long were cut as described (27), except that for all experiments other than that ofTable I, each internode was abraded (14) by stroking with an aqueous paste of No. 305 emery powder (Edmund Scientific, Barrington, NJ) which was then rinsed off by vigorous agitation in water, before cutting the segment. The segments were kept 2 to 3 h at 35C in moist air to deplete their GS activity (27).Lots of 30 segments, each in a small Stender dish, were pretreated usually for 30 to 60 min at 35°C in a medium containing 30 mm sucrose, 0.8 mm citric acid/Pipes (Tris salt) buffer pH 6.5 (unless specified otherwise in figure or table legends), containing usually 1 mM KCI, plus indicated additions. This pretreatment medium was removed and 2.0 ml of a similar incubation medium, with or without IAA or FC as indicated, the initial pH of which had been carefully measured to 0.01 pH unit with a semimicro glass electrode, were added, and the dishes were kept normally at 35C for 60 or 90 min (the incubation period). The incubation medium was removed and its pH was remeasured, while the segments were rinsed with ice water and held on ice until they were homogenized to prepare membranes for enzyme assay. H+ extrusion was estimated from the measured drop in pH (ApH) of the medium during incubation, using the postincubation titration curve

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