Exogenous polyamines alter membrane fluidity in bean leaves ? a basis for potential misinterpretation of their true physiological role

Roberts, Dane R.; Dumbroff, E. B.; Thompson, John E.

doi:10.1007/bf00391345

Cited by 139 publications

(79 citation statements)

References 34 publications

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“…Similar conclusions were reached some years ago with isolated beef heart mitochondria by Spisni et al (1976a,b). A surface-rigidifying effect of physiological polyamine concentrations was also found, with a similar method, in microsomes isolated from bean leaves or in liposomes composed of the lipids extracted from this material (Roberts et al, 1986). Taken together, these results indicate that polyamines can rigidify the membrane surface and this must be taken into account in order to explain their effect on membrane functions.…”

Section: Polyamines and Transportsupporting

confidence: 57%

Influence of polyamines on membrane functions

Schuber

1989

Biochemical Journal

421

222

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Section: Polyamines and Transportsupporting

confidence: 57%

Influence of polyamines on membrane functions

Schuber

1989

Biochemical Journal

421

222

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“…The study of polyamine transport across membranes proved to be a difficult task because multiple charged cations polyamines have a strong tendency to bind to negatively charged sites of the membranes such as phospholipids (1,16). In order to assess the extent of surface polyamine binding, isolated protoplasts and vacuoles were incubated with 14C-labeled spermidine (6.6 gM) and putrescine (5.5 gM) for 5 min and then were separated from the incubation medium by rapid centrifugation through a layer of silicone oil with or without the insertion of a washing layer of excess unlabeled polyamine.…”

Section: Resultsmentioning

confidence: 99%

Transport and Subcellular Localization of Polyamines in Carrot Protoplasts and Vacuoles

Pistocchi

Keller²,

Bagni³

et al. 1988

Plant Physiol.

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Putrescine and spermidine uptake in carrot (Daucus carota L., cv "Tip top") protoplasts and isolated vacuoles was studied. Protoplasts and vacuoles accumulated polyamines very quickly, with maximum absorption within 1 to 2 minutes. The insertion of a washing layer containing 100 millimolar unlabeled putrescine or spermidine did not change this pattern, but strongly reduced the uptake of putrescine and spermidine in protoplasts and in vacuoles. The dependence of spermidine uptake on the external concentration was linear up to the highest concentrations tested in protoplasts, while that in vacuoles showed saturation kinetics below 1 millimolar (Km = 61.8 micromolar) and a linear component from 1 to 50 millimolar. Spermidine uptake in protoplasts increased linearly between pH 5.5 and 7.0, while there was a distinct optimum at pH 7.0 for vacuoles. Preincubation of protoplasts with 1 millimolar Ca2+ affected only surface binding but not transport into the cells. Nonpermeant polycations such as La3+ and polylysine inhibited spermidine uptake into protoplasts. Compartmentation studies showed that putrescine and spermidine were partly vacuolar in location and that exogenously appfied spermidine could be recovered inside the cells. The characteristics of the protoplast and vacuolar uptake system induce us to put forward the hypothesis of a passive influx of polyamines through the plasmalemma and of the presence of a carrier-mediated transport system localized in the tonoplast.Polyamines are ubiquitous in higher plants. They may act as growth regulators, membrane stabilizers, senescence retardants, stress metabolites, and so forth (for reviews, see Refs. 5 and 18).For many of these functions, transport of polyamines has to be postulated. Recently, evidence has increased for both long and short distance transport of polyamines in higher plants (2,3,7,14,15 since cell fractionation studies revealed that most of the spermidine taken up by the cells (about 70%) had been adsorbed to the cell wall, whereas most of the putrescine taken up (70%) was recovered in the cytoplasm (15).From this differential subcellular distribution of polyamines, it is obvious that two overlapping processes have to be studied separately in order to gain the desired information on the uptake of polyamines: (a) the interactions of the positively charged polyamines with the negatively charged cell wall components and (b) the uptake of polyamines into the cell as a transport process across the plasmalemma (and then the tonoplast). The present study deals mainly with the second point.The availability of protoplasts and vacuoles had the added benefit of also allowing a study of the subcellular compartmentation of accumulated polyamines with the vacuole as the focal point. The vacuole as a temporary storage site of polyamines would explain the often observed discrepancy between the high intracellular polyamine concentrations of up to 1 mm and the low physiological concentrations needed for a proper functioning of the polyamines (10-100 ,uM) (4). Unf...

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“…According to this view, exogenous PAs are nonspecifically toxic, and thus prevent senescence by interfering with the formation of enzymes essential to the synthesis of ethylene. The decreased fluidity of membrane components in PA-treated cells is taken as evidence for this point of view (18).…”

mentioning

confidence: 99%

Polyamines in plant physiology.

Galston¹,

Sawhney²

1990

Plant Physiol.

587

258

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The diamine putrescine, the triamine spermidine, and the tetramine spermine are ubiquitous in plant cells, while other polyamines are of more limited occurrence. Their chemistry and pathways of biosynthesis and metabolism are well characterized.They occur in the free form as cations, but are often conjugated to small molecules like phenolic acids and also to various macromolecules. Their titer varies from approximately micromolar to more than millimolar, and depends greatly on environmental conditions, especially stress. In cereals, the activity of one of the major polyamine biosynthetic enzymes, arginine decarboxylase, is rapidly and dramatically increased by almost every studied external stress, leading to 50-fold or greater increases in putrescine titer within a few hours. The physiological significance of this increase is not yet clear, although most recent work suggests an adaptive, protective role. Polyamines produced through the action of ornithine decarboxylase, by contrast, seem essential for DNA replication and cell division. The application of exogenous polyamines produces effects on patterns of senescence and morphogenesis, suggesting but not proving a regulatory role for polyamines in these processes. The evidence for such a regulatory role is growing.

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Exogenous polyamines alter membrane fluidity in bean leaves ? a basis for potential misinterpretation of their true physiological role

Cited by 139 publications

References 34 publications

Influence of polyamines on membrane functions

Influence of polyamines on membrane functions

Transport and Subcellular Localization of Polyamines in Carrot Protoplasts and Vacuoles

Polyamines in plant physiology.

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