The Journal of Membrane Biology

, Volume 121, Issue 3, pp 223–236 | Cite as

Ion channels in the plasma membrane ofAmaranthus protoplasts: One cation and one anion channel dominate the conductance

  • B. R. Terry
  • S. D. Tyerman
  • G. P. Findlay


This report details preliminary findings for ion channels in the plasma membrane of protoplasts derived from the cotyledons ofAmaranthus seedlings. The conductance properties of the membrane can be described almost entirely by the behavior of two types of ion channel observed as single channels in attached and detached patches. The first is a cation-selective outward rectifier, and the second a multistate anion-selective channel which, under physiological conditions, acts as an inward rectifier.

The cation channel has unit conductance of approx. 30 pS (symmetrical 100 K+) and relative permeability sequence K+>Na+>Cl (1∶0.16∶0.03); whole-cell currents activate in a time-dependent manner, and both activation and deactivation kinetics are voltage dependent. The anion channel opens for hyperpolarized membrane potentials, has a full-level conductance of approx. 200 pS and multiple subconductance states. The number of sub-conductances does not appear to be fixed. When activated the channel is open for long periods, though shuts if the membrane potential (V m ) is depolarized; at millimolar levels of [Ca2+]cyt this voltage dependency disappears. Inward current attributable to the anion channel is not observed in whole-cell recordings when MgATP (2mm) is present in the intracellular solution. By contrast the channel is active in most detached patches, whether MgATP is present or not on the cytoplasmic face of the membrane. The anion channel has a significant permeability to cations, the sequence being NO 3 >Cl>K+>Aspartate (2.04∶1∶0.18 to 0.09∶0.04). The relative permeability for K+ decreased at progressively lower conductance states. In the absence of permeant anions this channel could be mistaken for a cation inward rectifier. The anion and cation channels could serve to clampV m at a preferred value in the face of events which would otherwise perturbV m .

Key Words

plant ion channels patch clamp plasma membrane anion channel cation channel multistate channel 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Beilby, M.J. 1985. Potassium channels atChara plasmalemma.J. Exp. Bot. 36:228–239Google Scholar
  2. Bisson, M.A. 1984. Calcium effects on electrogenic pump and passive permeability of the plasma membrane ofChara corallina.J. Membrane Biol. 81:59–67Google Scholar
  3. Boult, M., Elliott, D.C., Findlay, G.P., Terry, B.R., Tyerman, S.D. 1989. A multi-state anion channel in the plasmalemma ofAmaranthus tricolor.In: Plant Membrane Transport: The Current Position. J. Dainty, M.I. De Michelis, E. Marre, and F. Rasi-Caldigno, editors. pp. 517–520. Elsevier, AmsterdamGoogle Scholar
  4. Brown, D.A. 1990. G-proteins and potassium currents in neurons.Annu. Rev. Physiol. 52:215–242Google Scholar
  5. Bush, D.S., Hedrich, R., Schroeder, J.I. Jones, R.L. 1988. Channel-mediated K flux in barley aleurone protoplasts.Planta 176:368–377Google Scholar
  6. Coleman, H.A. 1986. Chloride currents inChara—A patch-clamp study.J. Membrane Biol. 93:55–61Google Scholar
  7. Coleman, H.A., Findlay, G.P. 1985. Ion channels in the membrane ofChara inflata.J. Membrane Biol. 83:109–118Google Scholar
  8. Cook, D.L., Hales, C.N. 1984. Intracellular ATP directly blocks K+ channels in pancreatic B-cells.Nature 311:271–273Google Scholar
  9. Coster, H.G. 1965. A quantitative analysis of the voltage-current relationships of fixed charge membranes and the associated property of “punch-through”Biophys. J. 5:669–686Google Scholar
  10. Coster, H.G.L. 1969. The role of pH in the punch-through effect in the electrical characteristics ofChara australis.Aust. J. Biol. Sci. 22:365–374Google Scholar
  11. Elliott, D.C. 1983. Inhibition of cytokinin-regulated responses by calmodulin-binding compounds.Plant Physiol. 72:215–218Google Scholar
  12. Elliott, D.C., Yao, Y.G. 1989. Cytokinin and fusicoccin effects on calcium transport inAmaranthus protoplasts.Plant Sci. 65:243–252Google Scholar
  13. Fairley, K., Laver, D., Walker, N.A. 1991. Whole-cell and single-channel currents across the plasmalemma of corn shoot suspension cells.J. Membrane Biol. (in press) Google Scholar
  14. Findlay, G.P., Coleman, H.A. 1983. Potassium channels in the membrane ofHydrodictyon africanum.J. Membrane Biol. 75:241–251Google Scholar
  15. Fox, J.A. 1987. Ion channel subconductance states.J. Membrane Biol. 97:1–8Google Scholar
  16. Geletyuk, V.I., Kazachenko, V.N. 1985. Single Cl channels in molluscan neurons: Multiplicity of the conductance states.J. Membrane Biol. 86:9–15Google Scholar
  17. Geletyuk, V.I., Kazachenko, V.N. 1989. Single potential-dependent K+ channels and their oligomers in molluscan glial cells.Biochim. Biophys. Acta 981:343–350Google Scholar
  18. Hamill, O.P., Marty, A., Neyer, E., Sakmann, B., Sigworth, F.J. 1981. Improved patch-clamp techniques for high-resolution current recording from cells and cell-free membrane patches.Pfluegers Arch. 391:85–100Google Scholar
  19. Hanke, W., Methfessel, C., Wilmsen, U., Boheim, G. 1984., Ion channel reconstitution into lipid bilayer membranes on glass patch pipettes.Bioelectrochem. Bioenergetics 12:329–339Google Scholar
  20. Hille, B. 1984. Ionic Channels of Excitable Membranes. Sinauer Associates, SunderlandGoogle Scholar
  21. Kataev, A.A., Zherelova, O.M., Berestovsky, G.N. 1984. Ca2+-induced activation and irreversible inactivation, of chloride channels in the perfused plasmalemma ofNitellopsis obtusa.Gen. Physiol. Biophys. 3:447–462Google Scholar
  22. Keller, B.U., Hedrich, R., Raschke, K. 1989. Voltage-dependent anion channels in the plasma membrane of guard cells.Nature 341:450–453Google Scholar
  23. Ketchum, K.A., Shrier, A., Poole, R.J. 1989. Characterisation of potassium-dependent currents in protoplasts of corn suspension cells.Plant Physiol. 89:1184–1192Google Scholar
  24. Kume, H., Takai, A., Tokumo, H., Tomita, T. 1989. Regulation of Ca2+-dependent K+-channel activity in tracheal myocytes by phosphorylation.Nature 341:152–154Google Scholar
  25. Lacerda, A.E., Rampe, D., Brown, A.M. 1988. Effects of protein kinase C activation on cardiac Ca2+ channels.Nature 335:249–251Google Scholar
  26. Levitan, I.B. 1985. Phosphorylation of ion channels.J. Membrane Biol. 87:177–190Google Scholar
  27. Lunevsky, V.Z., Zherelova, O.M., Vostrikov, I.Y., Berestovsky, G.N. 1983. Excitation ofCharaceae cell membranes as a result of activation of calcium and chloride channels.J. Membrane Biol. 72:43–58Google Scholar
  28. Lynch, E.C., Blake, M.S., Gotschlich, E.C., Mauro, A. 1984. Studies of porins: Spontaneously transferred from whole cells and reconstituted from purified proteins ofNeisseria gonorrhoeae andNeisseria meningitidis.Biophys. J. 45:104–107Google Scholar
  29. Moran, N., Satter, R.L. 1989. K+ channels in plasmalemma of motor cells ofSamanea saman.In: Plant Membrane Transport: The Current Position. J. Dainty, M.I. De Michelis, E. Marre, and F. Rasi Caldogno, editors. pp. 529–530. Elsevier, AmsterdamGoogle Scholar
  30. Noma, A. 1983. ATP-regulated K channels in cardiac muscle.Nature 305:147–148Google Scholar
  31. Ribalet, B., Ciani, S., Eddlestone, G.T. 1989. ATP-mediates both activation and inhibition of K(ATP) channel activity via cAMP-dependent protein kinase in insulin-secreting cell lines.J. Gen. Physiol. 94:693–717Google Scholar
  32. Rudy, B. 1988. Diversity and ubiquity of K channels.Neuroscience 25:729–749Google Scholar
  33. Schauf, C.L., Wilson, K.J. 1987. Properties of single K+ and Cl channels inAsclepias tuberosa protoplasts.Plant Physiol. 85:413–418Google Scholar
  34. Schroeder, J.I. 1988. K+ transport properties of K+ channels in the plasma membrane ofVicia faba guard cells.J. Gen. Physiol. 92:667–683Google Scholar
  35. Schroeder, J.I., Hagiwara, S. 1989. Cytosolic calcium regulates ion channels in the plasma membrane ofVicia faba guard cells.Nature 338:427–430Google Scholar
  36. Schroeder, J.I., Raschke, K., Neher, E. 1987. Voltage dependence of K+ channels in guard cell protoplasts.Proc. Natl. Acad. Sci. USA 84:4108–4112Google Scholar
  37. Shearman, M.S., Sekiguchi, K., Nishizuka, Y. 1989. Modulation of ion channel activity—a key function of the protein kinase-C enzyme family.Pharmacol. Rev. 41:211–237Google Scholar
  38. Shiina, T., Tazawa, M. 1987. Ca2+-activated Cl channel in plasmalemma ofNitellopsis obtusa.J. Membrane Biol. 99:137–146Google Scholar
  39. Sokolik, A.I., Yurin, V.M. 1986. Potassium channels in plasmalemma ofNitella cells at rest.J. Membrane Biol. 89:9–22Google Scholar
  40. Stoeckel, H., Takeda, K. 1989. Calcium-activated voltage-dependent non-selective cation currents in endosperm plasma membrane from higher plants.Proc R. Soc. London B. 237:213–231Google Scholar
  41. Tester, M. 1990. Plant ion channels: Whole-cell and single-channel studies.New Phytol. 114:305–340Google Scholar
  42. Tyerman, S.D., Findlay, G.P. 1989. Current-voltage curves of single Cl channels which coexist with two types of K+ channel in the tonoplast ofChara corallina.J. Exp. Bot. 40:105–118Google Scholar
  43. Tyerman, S.D., Findlay, G.P., Paterson, G.J. 1986a. Inward membrane current inChara inflata: II. Effects of pH, Cl-channel blockers and NH4+, and significance for the hyperpolarized state.J. Membrane Biol. 89:153–161Google Scholar
  44. Tyerman, S.D., Findlay, G.P., Paterson, G.J. 1986b. Inward membrane current inChara inflata: I. A voltage- and time-dependent Cl component.J. Membrane Biol. 89:139–152Google Scholar
  45. Tyerman, S.D., Findlay, G.P., Terry, B.R. 1989. Behaviour of K+ and Cl channels in the cytoplasmic drop membrane ofChara corallina using a transient detection method of analysing single-channel recordings.In: Plant Membrane Transport. J. Dainty, M.I. De Michelis, E. Marre, and F. Rasi-Caldogno, editors. pp. 173–178. Elsevier, AmsterdamGoogle Scholar
  46. Weik, R., Neumcke, B. 1989. ATP-sensitive potassium channels in adult mouse skeletal muscle: Characterization of the ATP-binding site.J. Membrane Biol. 110:217–226Google Scholar
  47. Williams, D.L., Jr., Katz, G.-M., Roy-Contancin, L., Reuben, J.P. 1988. Guanosine 5′-monophosphate modulates gating of high-conductance Ca2+-activated K+ channels in vascular smooth muscle cells.Proc. Natl. Acad. Sci. USA 85:9360–9364Google Scholar
  48. Zherelova, O.M. 1989. Activation of chloride channels in the plasmalemma ofNitella syncarpa by inositol 1,4,5-triphosphate.FEBS Lett. 249:105–107Google Scholar

Copyright information

© Springer-Verlag New York Inc. 1991

Authors and Affiliations

  • B. R. Terry
    • 1
  • S. D. Tyerman
    • 1
  • G. P. Findlay
    • 1
  1. 1.School of Biological SciencesThe Flinders University of South AustraliaBedford Park

Personalised recommendations