Summary
Regulation of ion-channel activity must take place in order to regulate ion transport. In case of tonoplast ion channels, this is possible on both the cytoplasmic and the vacuolar side. Isolated vacuoles of youngVigna unguiculata seedlings show no or hardly any channel activity at tonoplast potentials >80 mV, in the vacuole-attached configuration. When the configuration is changed to an excised patch or whole vacuole, a fast (excised patch) or slow (whole vacuole) increase of inward rectifying channel activity is seen. This increase is accompanied by a shift in the voltage-dependent gating to less hyperpolarized potentials. In the whole vacuole configuration the level of inward current increases and also the activation kinetics changes. Induction of channel activity takes up to 20 min depending on the age of the plants used and the diameter of the vacuole. On the basis of the estimated diffusion velocities, it is hypothesized that a compound with a mol wt of 20,000 to 200,000 is present in vacuoles of young seedlings, which shifts the population of channels to a less voltage-sensitive state.
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Alexandre, J., Lassalles, J.P., Kado, R.T. 1990. Opening of Ca++ channels in isolated red beet root vacuole membrane by inositol 1,4,5-triphosphate.Nature 343:567–570
Catterall, W.A. 1988. Structure and function of voltage-sensitive ion-channels.Science 242:50–61
Hedrich, R., Barbier-Brygoo, H., Felle, H., Fluegge, U.I., Luettge, U., Maathuis, F.J.M., Marx, S., Prins, H.B.A., Raschke, K., Schnabl, H., Schroeder, J.I., Struve, I., Taiz, L., Ziegler, P. 1988. General mechanisms for solute transport across the tonoplast of plant vacuoles: A patch clamp survey of ion-channels and proton pumps.Bot. Acta 101:7–13
Hedrich, R., Fluegge, U.I., Fernandez, J.M. 1986. Patch-clamp studies of ion transport in isolated plant vacuoles.FEBS Lett. 204:228–232
Hedrich, R., Neher, E. 1987. Cytoplasmic calcium regulates voltage-dependent ion-channels in plant vacuoles.Nature 329:833–835
Hedrich, R., Schroeder, J.I. 1989. The physiology of ion-channels and electrogenic pumps in higher plants.Annu. Rev. Plant Physiol. 40:539–569
Hille, B. 1984. Ionic channels of excitable membranes. Sinauer associates. Sunderland, MA
Hodgkin, A.L., Huxley, A.F. 1952. A quantitative description of membrane current and its application to conduction and excitability in nerve.J. Physiol. 117:500–544
Levitan, I.B. 1985. Phosphorylation of ion channels.J. Membrane Biol. 87:177–190
Maathuis, F.J.M., Prins, H.B.A. 1989. Patch clamp studies on root cell membranes of a salt tolerant and a salt sensitivePlantago species.In: Plant Membrane Transport: The Current Position. J. Dainty, M.I. DeMichelis, E. Marre, and F. Rasi-Caldogno, editors. pp. 521–524. Elsevier, Amsterdam
Maathuis, F.J.M., Prins, H.B.A. 1990. Electrophysiological membrane characteristics of the salt tolerantPlantago maritima and the salt sensitivePlantago media.Plant Soil 123:233–238
Schroeder, J.I. 1989. Quantitative analysis of outward rectifying K+ channel currents in guard cell protoplasts fromVicia faba.J. Membrane Biol. 107:229–235
Schubert, B., VanDongen, A.M.J., Kirsch, G.E., Brown, A.M. 1989. β-Adrenergic inhibition of cardiac sodium channels by dual G-protein pathways.Science 245:516–519
Walsh, K.B., Kass, R.S. 1988. Regulation of a heart potassium channel by protein kinase A and C.Science 242:67–69
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Ecotrans publication no. 27.
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Maathuis, F.J.M., Prins, H.B.A. Inhibition of inward rectifying tonoplast channels by a vacuolar factor: Physiological and kinetic implications. J. Membrain Biol. 122, 251–258 (1991). https://doi.org/10.1007/BF01871425
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DOI: https://doi.org/10.1007/BF01871425