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  • 1
    Electronic Resource
    Electronic Resource
    Active uptake of sucrose by plant plasma membrane vesicles: determination of some important physical and energetical parameters (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 82 (1991), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The present paper investigates some characteristics of plant plasma membrane vesicles in relation to sucrose uptake. The plasma membrane vesicles purified by aqueous two-phase partitioning from sugar beet (Beta vulgaris L.) leaf microsomes had an average diameter of 291 ± 13 nm and their internal volume was 2.2 μl (mg protein)−1. Although the vesicles were subjected to one freeze-thaw cycle for the purpose of storage, they retained mainly (78 %) their original right-side-out orientation as estimated either by labelling with peroxidase-labelled Concanavalin A or by measurements of ATPase latency. The use of higher concentrations of protecting agents [5 mM ethylenediaminetetraacetic acid (EDTA) and 2 mM dithiothreitol (DTT)] in the grinding buffer led to an increase of sucrose uptake by the vesicles. Measurements of the two components (pH and electrical gradients) of the proton motive force (PMF) showed that a high PMF (-200 mV) was created under the experimental conditions used. The accumulation of sucrose which theoretically could be obtained by this PMF is much larger than the accumulation actually measured. Although the data support the conclusion that an active uptake of sucrose is driven by the PMF in plasma membrane vesicles from sugar beet leaves, they also stress some limits of this experimental system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1991.tb02920.x
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  • 2
    Electronic Resource
    Electronic Resource
    Direct versus indirect effects of p-chloromercuribenzenesulphonic acid on sucrose uptake by plant tissues: The electrophysiological evidence (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 68 (1986), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The short-term effects of p-chloromercuribenzenesulphonic acid (PCMBS) on the transmembrane potential difference (PD) of broad bean (Vicia faba L. cv. Aguadulce) cotyledon cells and on sugar beet (Beta vulgaris L. cv. Klein E.) leaf cells were studied by the electrophysiological method. These effects were compared with that of the permeant thiol reagents N-ethylmaleimide and HgCl2. N-Ethylmaleimide and HgCl2 markedly and rapidly depolarised the PD of all the material studied, while PCMBS caused either a slight depolarisation (cotyledon cells) or no depolarisation (leaf cells) during the first 30 min of treatment. In cotyledons, PCMBS markedly inhibited sucrose uptake (89%) and the sucrose-induced depolarisation associated with the proton-sucrose symport (67%), while it decreased the proton-motive force only marginally (7%). It is concluded that during short treatments (30 min or less). PCMBS inhibits sucrose uptake directly by blocking the sucrose carrier, and not the proton pump. For longer treatments, indirect effects cannot be excluded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1986.tb03371.x
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  • 3
    Electronic Resource
    Electronic Resource
    Development of pH sensitivity of sucrose uptake during ageing of Vicia faba leaf discs (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 61 (1984), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Uptake of [U-14C]-sucrose (40 mM) by fresh and aged peeled leaf discs of broad bean (Vicia faba L. cv. Aguadulce) has been studied. In fresh discs, uptake was nearly insensitive to external pH, whereas the pH response of absorption in discs aged for 12 h was bell-shaped, with an optimum between pH 5 and 6. At this pH, uptake was nearly twice that in fresh tissue. The passive (insensitive to carbonyl cyanide m-chlorophenylhydrazone and to cold treatment) uptake was the same in fresh or aged discs. The development of pH sensitivity of absorption did not appear when ageing was performed in the presence of 10−HM cycloheximide or 5.7 × 10−5M actinomycin D. Similarly, when the tissues were treated with 10−3M spermidine for 2 h after excision and then aged for 10 h, the development of the pH-sensitive uptake system was inhibited. Ca2+ (10−2M) supplied together with spermidine prevented the inhibiting effect of spermidine. The appearance of the pH-sensitive system was also markedly reduced if ageing took place in the presence of 10−3M aminoethoxyvinylglycine. Autoradiographs from fresh discs and from discs aged with or without the inhibitors suggest that pH sensitivity developed more intensively in the parenchyma than in the veins.The results suggest some caution when using excised leaf discs for studies on sucrose uptake and phloem loading. Development of pH sensitivity of uptake may require the synthesis of both DNA-dependent RNA and protein and could be related to ethylene metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1984.tb05172.x
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  • 4
    Electronic Resource
    Electronic Resource
    Recognition of phlorizin by the carriers of sucrose and hexose in broad bean leaves (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 69 (1987), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Phlorizin (1-[2-(β-d-glucopyranosyloxy)-4, 6-dihydroxyphenyl]-3-(4-hydroxyphenyl)-1-propanone) is a well-known non-transported inhibitor of glucose uptake in animal cells. The effects of this compound were studied on the transmembrane potential difference (PD) of broad bean (Vicia faba L. cv. Aguadulce) mesophyll cells, and on the uptake of amino acids and sugars by the leaf tissues. Phlorizin (5 mM) induced a marginal depolarization (7 to 10 mV) of the normal PD (-140 mV), and a slight decrease in the uptake of glycine and serine. By contrast, phlorizin induced a stronger inhibition of the uptake of glucose and 3–O-methylglucose, and more particularly of sucrose uptake and phloem loading. In tissues aged for 12 h, 5 mM phlorizin inhibited the absorption of sucrose from a 1 mM solution by 70%. Kinetic experiments demonstrated that phlorizin acted as a competitive inhibitor for the sucrose carrier and for the hexose carrier. Efflux experiments showed that the counter-exchange of sucrose and of 3–O-methylglucose was also phlorizin-sensitive. Overall, the data show that phlorizin is recognized by the hexose carrier and, more efficiently, by the sucrose carrier of the material investigated, but that it is not transported across the membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1987.tb01978.x
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  • 5
    Electronic Resource
    Electronic Resource
    Changes in apoplastic and intracellular leaf sugars induced by the blocking of export in Vicia faba (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 68 (1986), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Sugar export by broadbean (Vicia faba L. cv. Aguadulce) was blocked by a cold jacket (1 cm-width, 1°C) applied on the petiole of a mature leaf or by heat-girdling the petiole. A time course study was made on the effects of these treatments on apoplastic and intracellular soluble sugars of the leaf in relation to phloem loading and photosynthesis. Blocking of export by heat-girdling induced an inhibition of phloem loading within 10 min, an accumulation of starch within 30 min and a rise in apoplastic sucrose within 60 min. By contrast, apoplastic hexoses and photosynthesis were not affected by this treatment within 8 h and intracellular sugars were not affected within 2 h. The cold jacket also increased the sucrose content of the apoplast. The increase in apoplastic sucrose induced by the cold barrier is reversed upon rewarming and less marked when the sink/source ratio is increased by defoliating all but the leaves studied. The results are discussed in terms of sink/source relationships. They show that the increase in apoplastic sucrose resulting from inhibition of loading is not part of the events leading from blocking of transport to change in carbon partitioning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1986.tb06610.x
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  • 6
    Electronic Resource
    Electronic Resource
    Carrier-mediated uptake of glyphosate in broad bean (Vicia faba) via a phosphate transporter (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 87 (1993), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The possibility that the herbicide glyphosate (N-phosphonomethylglycine) may be taken up in plant cells via a phosphate transporter of the plasma membrane was investigated using protoplasts of broad bean leaves (Vicia fabaL.). Phosphonoformic acid, a powerful inhibitor of phosphate transport in animal cells, was first demonstrated to be a competitive inhibitor of phosphate uptake inbroad bean protoplasts. Glyphosate was able to inhibit phosphate uptake into the protoplasts, and to protect partially the phosphate transporter from inhibition by phosphonoformic acid. Concentration dependence studies showed that glyphosate uptake exhibited a saturable phase at low glyphosate concentrations (0. 5 to 3 μM), superimposed by a linear uptake at higher concentrations (up to 100 μM). Inhibition of glyphosate uptake by para-chloromercuribenzene sulphonic acid, sodium azide and carbonyl-cyanide-m-chlorophenylhydrazone was much stronger at 1 than at 100 μM glyphosate. Kinetics indicated that the saturable component of glyphosate transport was competitively inhibited by either phosphate or phosphonoformic acid. It is concluded that glyphosate can be absorbed via a phosphate transporter of the plasma membrane
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1993.tb02508.x
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  • 7
    Electronic Resource
    Electronic Resource
    Phloem loading in Vicia faba leaves: Effect of N-ethylmaleimide and parachloromercuribenzenesulfonic acid on H+ extrusion, K+ and sucrose uptake (1980)
    Springer
    Planta 149 (1980), S. 144-148 
    Details
    ISSN: 1432-2048
    Keywords: Phloem loading ; Potassium uptake ; Proton extrusion ; Sucrose uptake ; Sulfhydryl-specific reagents ; Uptake (H+, K+, sucrose) ; Vicia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of a penetrating (NEM) and a non-penetrating (PCMBS) sulfhydryl-specific reagent on proton extrusion, 86Rb and [U-14C]sucrose uptake by Vicia faba leaves have been studied. Proton extrusion was strongly or completely inhibited by 0.1 mM NEM. 86Rb and [U-14C]sucrose uptake were markedly reduced by NEM concentrations equal to or higher than 0.5 mM. Under our experimental conditions, PCMBS (1 mM) exerted a strong inhibition on [14C]sucrose uptake but did not inhibit proton extrusion and 86Rb uptake. The sensitivity of phloem loading to PCMBS is thought to be a consequence of sugar-carrier blockage and not of inhibition of the proton pump.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00380875
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  • 8
    Electronic Resource
    Electronic Resource
    Dipeptide transport in barley mesophyll vacuoles (1995)
    Springer
    Planta 196 (1995), S. 430-433 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The transport of [14C]glycyl-glycine (Gly-Gly) across the tonoplast of isolated barley vacuoles has been characterized. Uptake of the dipeptide Gly-Gly into barley mesophyll vacuoles was strongly increased by the addition of ATP, while Mg2+ inhibited the ATP-dependent fluxes. Inhibition of the vacuolar proton pump by bafilomycin or dissipation of the ΔpH had no effect on the ATP-dependent Gly-Gly uptake. Only the non-hydrolysable ATP analogue 5′-adenylylimidodiphosphate could partially substitute for ATP; ADP, GTP and UTP had no effect. Transport of Gly-Gly was saturable exhibiting an apparent K m of 49±5 mM. Uptake was inhibited by the sulphydryl reagents N-ethylmaleimide and p-chloromercuribenzenesulphonic acid. When present at 30 mM, various dipeptides as well as tri-glycine inhibited Gly-Gly (10 mM) uptake by 30–50%, whereas 5 mM phenylalanine was able to inhibit Gly-Gly uptake almost completely. Comparison with published data suggests that Gly-Gly is transferred across the tonoplast by the same system as several amino acids and inorganic ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203640
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  • 9
    Electronic Resource
    Electronic Resource
    Glutathione depletion leads to delayed growth stasis in Saccharomyces cerevisiae : evidence of a partially overlapping role for thioredoxin (2000)
    Springer
    Current genetics 38 (2000), S. 71-77 
    Details
    ISSN: 1432-0983
    Keywords: Key words Glutathione ; Thioredoxin ; Growth stasis ; S. cerevisiae ; S. pombe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Disruption of the first enzyme of glutathione biosynthesis in both Saccharomyces cerevisiae and Schizosaccharomyces pombe leads to a glutathione auxotrophy phenotype on plates. However, growth experiments in liquid medium revealed that the cessation of growth resulting from glutathione depletion in these yeasts is very delayed in S. cerevisiae compared to S. pombe. Glutathione metabolism was investigated to understand this delayed growth stasis in S. cerevisiae. The assimilation of reduced and oxidized glutathione, the intracellular storage pools of glutathione and the turnover of this compound were investigated and found to be similar in both yeasts. A possible overlapping role of intracellular thioredoxin in causing delayed stasis was studied. Yeast thioredoxin was overexpressed in S. cerevisiae and was found to partially relieve the dependence of S. cerevisiae glutathione auxotrophs on extracellular glutathione in glucose-grown cultures, as well as in glycerol-grown cultures where conditions of increased glutathione requirements exists in the cell. By partially, but not completely, compensating for glutathione deficiency in this yeast, thioredoxin thus appeared to be the major factor that was causing the delayed growth stasis following glutathione depletion in this yeast.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002940000137
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  • 10
    Electronic Resource
    Electronic Resource
    Stimulation of sugar exit from leaf tissues ofVicia faba L. (1988)
    Springer
    Planta 174 (1988), S. 340-348 
    Details
    ISSN: 1432-2048
    Keywords: Carrier specificity ; Hexose transport ; Leaf (sugar transport) ; Membrane (sugar transport) ; Sucrose transport ; Vicia (sugar transport)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract After removal of the lower epidermis, leaf discs ofVicia faba L. were loaded with either [14C]sucrose or [3H]3-O-methylglucose (3-O-MeG). The exit of preloaded sucrose was strongly stimulated when sucrose was present in the bathing medium, and the exit of 3-O-MeG was also markedly increased in the presence of 3-O-MeG. This specific stimulation exhibited single saturation dependence on the external concentration of sugar (K m=9 mM for sucrose, 5 mM for 3-O-MeG), and was sensitive to low temperature, uncouplers and thiol reagents. Sucrose exit was never affected by 3-O-MeG in the bathing medium. Sucrose did not affect the exit of 3-O-MeG in fresh discs, but promoted this exit in discs previously aged for 12 h, indicating partial external hydrolysis of sucrose in the latter tissues. Ageing also dramatically increased the exit of 3-O-MeG induced by 3-O-MeG but had no effect on the exit of sucrose induced by sucrose. The ability of 53 compounds (pentoses, hexoses, hexose-phosphates, polyols, di- and trisaccharides, phenyl- and nitrophenyl-derivatives, sweeteners) to interact with the sucrose carrier and with the hexose carrier was tested. Sucrose, maltose, α-phenylglucoside andp-nitrophenyl-α-glucoside interacted with the sucrose carrier.d-glucose,d-xylose,d-fucose,d-galactose,d-mannose, 3-O-MeG and 2-deoxyglucose interacted with the hexose carrier.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00959519
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