A model for proton and potassium co-transport during the uptake of glutamine and sucrose by tomato internode disks

Bel, Aart J. E. van; Erven, A.J. Van

doi:10.1007/bf00379930

Cited by 37 publications

(24 citation statements)

References 25 publications

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“…1). The apparent conflict between this latter finding and that of van Bel (21) is probably resolved by the fact that initial flux was observed in our investigation whereas his measurements were made after some hours. This strict pH dependence even in the presence of CCCP, together with the very similar pH dependence of vacuolar uptake although the direction of the protonmotive force is here reversed (14) are strong indications that the pH sensitivity may reflect a requirement of a constituent of the transport system for protonation and is not necessarily reflecting the energy input for transport.…”

Section: Discussioncontrasting

confidence: 81%

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Protonation and Light Synergistically Convert Plasmalemma Sugar Carrier System in Mesophyll Protoplasts to its Fully Activated Form

Guy¹,

Reinhold²,

Rahat³

et al. 1981

Plant Physiol.

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The course of sugar fluxes into and out of protoplasts isolated from the mesophyll of Pisum sativum L. has been followed over brief time intervals (minutes). Light strongly stimulated net sugar influx at pH 8 as well as at pH 5.5. The proton conductor carbonyl cyanide m-chlorophenylhydrazone (CCCP) inhibited initial influx in the light, both at pH 8.0 and at pH 5.5. CCCP was without effect in the dark at either pH. All these results applied both to sucrose and to the nonmetabolizable glucose analog 3-0-methyl-Dglucose.When protoplasts at pH 5.5 were transferred from light to darkness, "stored" light driving force maintained uptake in the dark at the full light rate for the first 7 minutes. At pH 8, however, even 4 minutes after transfer to dark, uptake was well below the light rate. Initial uptake rates over a range of external concentrations were derived from progress curves obtained in the light and in the dark, both at pH 5.5 and at 7.7. When initial rate was plotted against concentration, simple Michaelis-Menten kinetics were observed only under the condition pH 5.5, light. In the dark at both pH values, and in the light at pH 7.7, complex curves with intermediate plateaus were obtained, strongly resembling curves reported for systems where mixed negative and positive cooperativity is operating.The same "K,. for protons" was observed in the dark and in the light (10-7 molar). Switching protoplasts in the dark from pH 8 to 5.5 failed to drive sugar transport by imposed protonmotive force, as judged by lack of sensitivity to CCCP. Switching protoplasts which had taken up sugar in the dark at pH 5.5 to pH 7 induced net efflux of sugar. Flux analysis showed that this effect was entirely due to the prompt fall in influx.

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Section: Discussioncontrasting

confidence: 81%

“…Under both conditions, uptake is proceeding unaided by the proton extrusion pump-in the former case because the latter is short-circuited by the proton conductor, and in the latter case because it may require light to activate the pump in our cells (cf. 15,17,18,21). Yet dark uptake does not appear to be facilitated diffusion.…”

Section: Discussionmentioning

confidence: 99%

Protonation and Light Synergistically Convert Plasmalemma Sugar Carrier System in Mesophyll Protoplasts to its Fully Activated Form

Guy¹,

Reinhold²,

Rahat³

et al. 1981

Plant Physiol.

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“…It has been proposed that phloem loading of sucrose in Beta proceeds by means of a sucrose-proton cotransport mechanism (10,12,13). Similar sucrose cotransport systems have been reported in castor bean cotyledons (15,18), soybean cotyledons (20,21), Samanea pulvinar organs (23), maize scutellum (14), tomato internodes (26), castor bean petiolar phloem (22), and Vicia minor vein phloem (5), leading Giaquinta (12) to propose that cotransport may be the general mechanism by which sucrose is transported in higher plants.…”

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confidence: 64%

A Reanalysis of the Two-Component Phloem Loading System in Beta vulgaris

Maynard¹,

Lucas²

1982

Plant Physiol.

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“…The literature has been reviewed (2). In recent studies, proton co-transport has been implicated in pea-stem segments (4, 5), maize coleoptiles and roots (4), intact duckweed (18,20), tomato internode segments and discs (21,22), sugar-beet leaves (9), and isolated protoplasts and vacuoles from pea-leaf mesophyll cells (10,11 with test medium, and gently resuspended in test medium. Large quantities of germinated pollen were allowed to settle for 5 min in a tall glass cylinder in order to decant about 0.5 volume prior to filtering.…”

mentioning

confidence: 99%

“…The literature has been reviewed (2). In recent studies, proton co-transport has been implicated in pea-stem segments (4,5), maize coleoptiles and roots (4), intact duckweed (18,20), tomato internode segments and discs (21,22), sugar-beet leaves (9), and isolated protoplasts and vacuoles from pea-leaf mesophyll cells (10,11). Use of highly differentiated tissue, such as Ricinus cotyledons (12,13), creates certain difficulties in comparing the relationship between proton motive force and sugar uptake.…”

mentioning

confidence: 99%

Sugar Uptake in Lily Pollen

Deshusses¹,

Gumber²,

Loewus³

1981

Plant Physiol.

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The data presented here are consistent with a proton-sugar co-transport in germinated pollen of Lilium longiflorum Thunb. Optimal uptake occurs at pH 5.0. A Km of 1.7 to 1.8 millimolar is obtained from the initial rate of pH change induced by sucrose uptake as well as from uptake of IU-`4C1-sucrose. The energy of activation is -11 kilocalories mole-'. The effect of several inhibitors and sugar competitors on IU-'4Clsucrose and D-IU-`4C1 glucose uptake is given. The possibility of hydrolysis of sucrose prior to its transport into the poUlen tube has been considered and reasons for choosing a sucrose-type uptake are presented. The possible in vivo significance of this co-transport process during pollen germination is discussed. Germinated pollen has features to recommend it as an experimental system of choice for studies of sugar uptake.Proton co-transport of sugar as first-described in Chlorella (15) is now known to occur in higher plants and is probably a process found in all species. The literature has been reviewed (2). In recent studies, proton co-transport has been implicated in pea-stem segments (4, 5), maize coleoptiles and roots (4), intact duckweed (18,20), tomato internode segments and discs (21,22), sugar-beet leaves (9), and isolated protoplasts and vacuoles from pea-leaf mesophyll cells (10,11 with test medium, and gently resuspended in test medium. Large quantities of germinated pollen were allowed to settle for 5 min in a tall glass cylinder in order to decant about 0.5 volume prior to filtering. In some studies, resuspended pollen was held for periods up to 2 h at 20 C without impairment of cytoplasmic streaming and with little additional tube elongation (see "Results" and Table II).Measurements. In pH studies, germinated pollen (usually 50 mg) was resuspended in 3.5 ml test medium at 28 C in a thermostated titration vessel (Metrohm, Herisau, Switzerland). A fine stream of air bubbles kept the pollen in suspension. pH changes were measured with a combination glass electrode (Radiometer GK2321-C) and were recorded with a 1-mv Varian A-5 recorder.The initial rate ofproton uptake was calculated from the difference in slope of the pH curve before and after addition of sugar to the medium.In uptake studies involving labeled sucrose, 1 ml pollen suspension was added to 1 ml 100 mm Mes/Ca buffer at pH 5.0 [Mes buffer was adjusted to the indicated pH with Ca(OH)2] and held for 2 min to attain 28 C. One-half ml sugar analog, inhibitor, or test medium was added and, 0.5 min later, 0.5 ml 6 mm [U-'4C]sucrose was added. The final concentration of sucrose was 1 mM. Addition of label was taken as zero time. After incubation, uptake was terminated by filtering l-ml aliquots on 0.8-,am membranes and washing the pollen with 3 ml test medium. The washed pollen and its membrane support were transferred to 5 ml "tritosol" (8) and counted in a Packard model 3320 liquid scintillation spectrometer at a 14C efficiency of 70%.To characterize the nature of labeled products of [U-_4C]sucrose uptake after transport...

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A model for proton and potassium co-transport during the uptake of glutamine and sucrose by tomato internode disks

Cited by 37 publications

References 25 publications

Protonation and Light Synergistically Convert Plasmalemma Sugar Carrier System in Mesophyll Protoplasts to its Fully Activated Form

Protonation and Light Synergistically Convert Plasmalemma Sugar Carrier System in Mesophyll Protoplasts to its Fully Activated Form

A Reanalysis of the Two-Component Phloem Loading System in Beta vulgaris

Sugar Uptake in Lily Pollen

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