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2013-07-31Zeitschriftenartikel DOI: 10.3389/fpls.2013.00274
Electrophysiological approach to determine kinetic parameters of sucrose uptake by single sieve elements or phloem parenchyma cells in intact Vicia faba plants
dc.contributor.authorHafke, Jens B.
dc.contributor.authorHöll, Sabina-Roxana
dc.contributor.authorKühn, Christina
dc.contributor.authorvan Bel, Aart J. E.
dc.date.accessioned2019-12-17T12:10:46Z
dc.date.available2019-12-17T12:10:46Z
dc.date.issued2013-07-31none
dc.date.updated2019-10-08T17:04:06Z
dc.identifier.urihttp://edoc.hu-berlin.de/18452/21707
dc.description.abstractApart from cut aphid stylets in combination with electrophysiology, no attempts have been made thus far to measure in vivo sucrose-uptake properties of sieve elements. We investigated the kinetics of sucrose uptake by single sieve elements and phloem parenchyma cells in Vicia faba plants. To this end, microelectrodes were inserted into free-lying phloem cells in the main vein of the youngest fully-expanded leaf, half-way along the stem, in the transition zone between the autotrophic and heterotrophic part of the stem, and in the root axis. A top-to-bottom membrane potential gradient of sieve elements was observed along the stem (−130 mV to −110 mV), while the membrane potential of the phloem parenchyma cells was stable (approx. −100 mV). In roots, the membrane potential of sieve elements dropped abruptly to −55 mV. Bathing solutions having various sucrose concentrations were administered and sucrose/H+-induced depolarizations were recorded. Data analysis by non-linear least-square data fittings as well as by linear Eadie–Hofstee (EH) -transformations pointed at biphasic Michaelis–Menten kinetics (2 MM, EH: Km1 1.2–1.8 mM, Km2 6.6–9.0 mM) of sucrose uptake by sieve elements. However, Akaike's Information Criterion (AIC) favored single MM kinetics. Using single MM as the best-fitting model, Km values for sucrose uptake by sieve elements decreased along the plant axis from 1 to 7 mM. For phloem parenchyma cells, higher Km values (EH: Km1 10 mM, Km2 70 mM) as compared to sieve elements were found. In preliminary patch-clamp experiments with sieve-element protoplasts, small sucrose-coupled proton currents (−0.1 to −0.3 pA/pF) were detected in the whole-cell mode. In conclusion (a) Km values for sucrose uptake measured by electrophysiology are similar to those obtained with heterologous systems, (b) electrophysiology provides a useful tool for in situ determination of Km values, (c) As yet, it remains unclear if one or two uptake systems are involved in sucrose uptake by sieve elements, (d) Affinity for sucrose uptake by sieve elements exceeds by far that by phloem parenchyma cells, (e) Patch-clamp studies provide a feasible basis for quantification of sucrose uptake by single cells. The consequences of the findings for whole-plant carbohydrate partitioning are discussed.eng
dc.language.isoengnone
dc.publisherHumboldt-Universität zu Berlin
dc.rights(CC BY 3.0) Attribution 3.0 Unportedger
dc.rights.urihttp://creativecommons.org/licenses/by/3.0/
dc.subjectAkaike's Information Criterioneng
dc.subjectcarbohydrate partitioningeng
dc.subjectEadie–Hofstee plotseng
dc.subjectH+/sucrose symportereng
dc.subjectKm valueseng
dc.subjectnon-linear least-square fittingseng
dc.subjectphloem parenchyma cells sieve-element/companion cell complexeng
dc.subjectsucrose-induced depolarization of membrane potentialeng
dc.subject.ddc570 Biologienone
dc.titleElectrophysiological approach to determine kinetic parameters of sucrose uptake by single sieve elements or phloem parenchyma cells in intact Vicia faba plantsnone
dc.typearticle
dc.identifier.urnurn:nbn:de:kobv:11-110-18452/21707-6
dc.identifier.doi10.3389/fpls.2013.00274none
dc.identifier.doihttp://dx.doi.org/10.18452/20955
dc.type.versionpublishedVersionnone
local.edoc.container-titleFrontiers in Plant Sciencenone
local.edoc.pages11none
local.edoc.type-nameZeitschriftenartikel
local.edoc.institutionLebenswissenschaftliche Fakultätnone
local.edoc.container-typeperiodical
local.edoc.container-type-nameZeitschrift
local.edoc.container-publisher-nameFrontiers Media S.A.none
local.edoc.container-publisher-placeLausannenone
local.edoc.container-volume4none
dc.description.versionPeer Reviewednone
local.edoc.container-articlenumber274none
dc.identifier.eissn1664-462X

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