K+ channels of stomatal guard cells: Abscisic-acid-evoked control of the outward rectifier mediated by cytoplasmic pH
- 307 Downloads
- 92 Citations
Abstract
The activation by abscisic acid (ABA) of current through outward-rectifying K+ channels and its dependence on cytoplasmic pH (pHi) was examined in stomatal guard cells of Vicia faba L. Intact guard cells were impaled with multibarrelled and H+-selective microelectrodes to record membrane potentials and pHi during exposures to ABA and the weak acid butyrate. Potassium channel currents were monitored under voltage clamp and, in some experiments, guard cells were loaded with pH buffers by iontophoresis to suppress changes in pHi. Following impalements, stable pHi values ranged between 7.53 and 7.81 (7.67±0.04, n = 17). On adding 20 μM ABA, pHi rose over periods of 5–8 min to values 0.27±0.03 pH units above the pHi before ABA addition, and declined slowly thereafter. Concurrent voltage-clamp measurements showed a parallel rise in the outward-rectifying K+ channel current (IK, out) and, once evoked, both pHi and IK, out responses were unaffected by ABA washout. Acid loads, imposed with external butyrate, abolished the ABA-evoked rise in IK, out. Butyrate concentrations of 10 and 30 mM (pH0 6.1) caused pHi to fall to values near 7.0 and below, both before and after adding ABA, consistent with a cytoplasmic buffer capacity of 128±12 mM per pH unit (n = 10) near neutrality. Butyrate washout was characterised by an appreciable alkaline overshoot in pHi and concomitant swell in the steady-state conductance of IK, out. The rise in pHi and iK, out in ABA were also virtually eliminated when guard cells were first loaded with pH buffers to raise the cytoplasmic buffer capacity four- to sixfold; however, buffer loading was without appreciable effect on the ABA-evoked inactivation of a second, inward-rectifying class of K+ channels (IK, in). The pHi dependence of IK, out was consistent with a cooperative binding of at least 2H+ (apparent pKa = 8.3) to achieve a voltage-independent block of the channel. These results establish a causal link previously implicated between cytoplasmic alkalinisation and the activation of IK, out in ABA and, thus, affirm a role for H+ in signalling and transport control in plants distinct from its function as a substrate in H+-coupled transport. Additional evidence implicates a coordinate control of IK, in by cytoplasmic-free [Ca2+] and pHi.
Key words
Ion channel block (pH dependence) Potassium channel (inward-rectifier, outward-rectifier) Signal transduction (pHi and Ca2+ dependence) Vicia guard cellAbbreviations
- ABA
abscisic acid
- [Ca2+]i
cytoplasmic free [Ca2+]i
- EK
K+ equilibrium potential
- IK, out, IK, in
outward-, inward-rectifying K+ channel (current)
- I-V
current-voltage (relation)
- Mes
2-(N-morpholino)ethanesulfonic acid
- pHi
cytoplasmic pH
- Tes
2-{[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]-amino}ethanesulfonic acid
- Vm
membrane potential
Preview
Unable to display preview. Download preview PDF.
References
- Armstrong, C.M. (1971) Interaction of tetraethylammonium ion derivatives with the potassium channels of giant axons. J. Gen. Physiol. 58, 413–437Google Scholar
- Bates, G.W., Goldsmith, M.H.M. (1983) Rapid response of the plasma membrane potential in oat coleoptiles to auxin and other weak acids. Planta 159, 231–237Google Scholar
- Bentrup, F.-W., Gogarten-Boekels, M., Hoffmann, B., Gogarten, J., Baumann, C. (1986) ATP-dependent acidification and tonoplast hyperpolarization in isolated vacuoles from green suspension cells of Chenopodium rubrum. Proc. Natl. Acad. Sci. USA 83, 2431–2433Google Scholar
- Bertl, A., Felle, H. (1985) Cytoplasmic pH of root hair cells of Sinapis alba recorded by a pH-sensitive microelectrode. Does fusicoccin stimulate the proton pump by cytoplasmic acidification? J. Expt. Bot. 36, 1142–1149Google Scholar
- Blackford, S., Rea, P.A., Sanders, D. (1990) Voltage sensitivity of H+/Ca2+ antiport in higher plant tonoplast suggests a role in vacuolar calcium accumulation. J. Biol. Chem. 265, 9617–9620Google Scholar
- Blatt, M.R. (1987a) Electrical characteristics of stomatal guard cells: the contribution of ATP-dependent, “electrogenic” transport revealed by current-voltage and difference-current-voltage analysis. J. Membr. Biol. 98, 257–274Google Scholar
- Blatt, M.R. (1987b) Electrical characteristics of stomatal guard cells: the ionic basis of the membrane potential and the consequence of potassium chloride leakage from microelectrodes. Planta 170, 272–287Google Scholar
- Blatt, M.R. (1988) Potassium-dependent bipolar gating of potassium channels in guard cells. J. Membr. Biol. 102, 235–246Google Scholar
- Blatt, M.R. (1990) Potassium channel currents in intact stomatal guard cells: rapid enhancement by abscisic acid. Planta 180, 445–455Google Scholar
- Blatt, M.R. (1991a) Ion channel gating in plants: physiological implications and integration for stomatal function. J. Membr. Biol. 124, 95–112Google Scholar
- Blatt, M.R. (1991b) A primer in plant electrophysiological methods. In: Methods in plant biochemistry, pp 281–321, Hostettmann, K., ed. Academic Press, LondonGoogle Scholar
- Blatt, M.R. (1992) K+ channels of stomatal guard cells: characteristics of the inward rectifier and its control by pH. J. Gen. Physiol. 99, 615–644Google Scholar
- Blatt, M.R., Clint, G.M. (1989) Mechanisms of fusicoccin action: Kinetic modification and inactivation of potassium channels in guard cells. Planta 178, 509–523Google Scholar
- Blatt, M.R., Slayman, C.L. (1983) KCl leakage from microelectrodes and its impact on the membrane parameters of a nonexcitable cell. J. Membr. Biol. 72, 223–234Google Scholar
- Blatt, M.R., Slayman, C.L. (1987) Role of “active” potassium transport in the regulation of cytoplasmic pH by nonanimal cells. Proc. Natl. Acad. Sci. USA 84, 2737–2741Google Scholar
- Blatt, M.R., Thiel, G. (1993) Hormonal control of ion channel gating. Annu. Rev. Plant Physiol. Mol. Biol. 44, in pressGoogle Scholar
- Blatt, M.R. Thiel, G., Trentham, D.R. (1990) Reversible inactivation of K+ channels of Vicia stomatal guard cells following the photolysis of caged inositol 1,4,5-trisphosphate. Nature 346, 766–769Google Scholar
- Blumwald, E., Cragoe, E.J.J., Poole, R.J. (1987) Inhibition of Na+/ H+ antiport activity in sugar beet tonoplast by analogs of amiloride. Plant Physiol. 85, 30–33Google Scholar
- Blumwald, E., Poole, R.J. (1987) Salt tolerance in suspension cultures of sugar beet: induction of Na+/H+ antiport activity at the tonoplast by growth in salt. Plant Physiol. 83, 884–887Google Scholar
- Boron, W.F. (1977) Intracellular pH transients in giant barnacle muscle fibers. Am. J. Physiol. 233, C61-C73Google Scholar
- Busa, W.B. (1986) Mechanisms and consequences of pH-mediated cell regulation. Annl. Rev. Physiol. 48, 389–402Google Scholar
- Christensen, O., Zeuthen, T. (1987) Maxi K+ channels in leaky epithelia are regulated by intracellular Ca2+, pH and membrane potential. Pfluegers Arch. European J. Physiol. 408, 249–259Google Scholar
- Clint, G.M. (1984) Ionic relations of stomatal guard cells, pp. 1–187, Ph.D. thesis, University of Cambridge, CambridgeGoogle Scholar
- Clint, G.M., MacRobbie, E.A.C. (1987) Sodium efflux from perfused giant algal cells. Planta 171, 247–253Google Scholar
- Danthuluri, N.R., Kim, D., Brock, T.A. (1990) Intracellular alkalinization leads to Ca2+ mobilization from agonist-sensitive pools in bovine aortic endothelial cells. J. Biol. Chem. 265, 19071–19076Google Scholar
- Davies, N.W. (1990) Modulation of ATP-sensitive K+ channels in skeletal muscle by intracellular protons. Nature 343, 375–377Google Scholar
- Epel, D., Dube, F. (1987) Intracellular pH and cell proliferation. In: Control of animal cell proliferation, pp. 363–394, Epel, D., ed. Academic Press, New YorkGoogle Scholar
- Fairley, G.K., Assmann, S.M. (1991) Evidence for G-protein regulation of inward potassium ion channel current in guard cells of fava bean. Plant Cell 3, 1037–1044Google Scholar
- Felle, H. (1987) Proton transport and pH control in Sinapis alba root hairs: a study carried out with double-barrelled pH microelectrodes. J. Exp. Bot. 340, 354Google Scholar
- Felle, H. (1988) Auxin causes oscillations of cytosolic free calcium and pH in Zea mays coleoptiles. Planta 174, 495–499Google Scholar
- Felle, H. (1989) pH as a second messenger in plants. In: Second messengers in plant growth and development, pp. 145–166, Boss, W.F., Morre, D.J., eds. Alan R. Liss, Inc., New YorkGoogle Scholar
- Felle, H., Peters, W., Palme, K. (1991) The electrical response of maize to auxins. Biochim. Biophys. Acta 1064, 199–204Google Scholar
- French, R.J., Shoukimas, J.J. (1985) An ion's view of the potassium channel: the structure of the permeation pathway as sensed by a variety of blocking ions. J. Gen. Physiol. 85, 669–698Google Scholar
- Fricker, M.D., Gilroy, S., Read, N.D., Trewavas, A.J. (1991) Visualisation and measurement of the calcium message in guard cells. In: Molecular biology of plant development, pp. 177–190, Schuch, W., Jenkins, G., eds. Cambridge University Press, CambridgeGoogle Scholar
- Gehring, C.A., Irving, H.R., Parish, R.W. (1990) Effects of auxin and abscisic acid on cytosolic calcium and pH in plant cells. Proc. Natl. Acad. Sci. USA 87, 9645–9649Google Scholar
- Gilroy, S., Fricker, M.D., Read, N.D., Trewavas, A.J. (1991) Role of calcium in signal transduction of Commelina guard cells. Plant Cell 3, 333–344Google Scholar
- Grandin, N., Charbonneau, M. (1992) The increase in intracellular pH associated with Xenopus egg activation is a Ca2+-dependent wave. J. Cell Sci. 101, 55–67Google Scholar
- Hagiwara, S., Myazaki, S., Moody, W., Patlak, J. (1978) Blocking effects of barium and hydrogen ions on the potassium current during anomalous rectification in the starfish egg. J. Physiol. 279, 167–185Google Scholar
- Hanrahan, J.W., Tabcharani, J.A. (1990) Inhibition of an outwardly rectifying anion channel by HEPES and related buffers. J. Membr. Biol. 116, 65–77Google Scholar
- Harris, M.J., Outlaw, W.H. Jr. (1991) Rapid adjustment of guard-cell abscisic acid levels to current leaf-water status. Plant Physiol. 95, 171–173Google Scholar
- Hedrich, R., Kurkdjian, A., Guern, J., Fluegge, U.I. (1989) Comparative studies on the electrical properties of the H+ translocating ATPase and pyrophosphatase of the vacuolar-lysosomal compartment. EMBO J. 8, 2835–2841Google Scholar
- Hedrich, R., Busch, H., Raschke, K. (1990) Ca2+ and nucleotide dependent regulation of voltage dependent anion channels in the plasma membrane of guard cells. EMBO J. 9, 3889–3892Google Scholar
- Hill, A.V. (1910) The possible effects of the aggregation of the molecules of hemoglobin on its dissociation curves. J. Physiol. 40, 4–7Google Scholar
- Hodgkin, A.L., Huxley, A.F., Katz, B. (1952) Measurements of current-voltage relations in the membrane of the giant axon of Loligo. J. Physiol. 116, 424–448Google Scholar
- Hosoi, S., Iino, M., Shimazaki, K. (1988) Outward-rectifying K+ channels in stomatal guard cell protoplasts. Plant Cell Physiol. 29, 907–911Google Scholar
- Irving, H.R., Gehring, C.A., Parish, R.W. (1992) Changes in cytosolic pH and calcium of guard cells precede stomatal movements. Proc. Natl. Acad. Sci. USA 89, 1790–1794Google Scholar
- Johnson, C.H., Epel, D. (1981) Intracellular pH of sea urchin eggs measured by the dimethyloxazolidinedione (DMO) method. J. Cell Biol. 89, 284–291Google Scholar
- Kurkdjian, A., Guern, J. (1989) Intracellular pH: measurement and importance in cell activity. Annu. Rev. Plant. Physiol. Mol. Biol. 40, 271–303Google Scholar
- Laurido, C., Candia, S., Wolff, D., Latorre, R. (1991) Proton modulation of Ca2+-activated K+ channel from rat skeletal muscle incorporated into planat bilayers. J. Gen. Physiol. 98, 1025–1043Google Scholar
- Lukacs, G.L., Moczydlowski, E. (1990) A chloride channel from lobster walking leg nerves. J. Gen. Physiol. 96, 707–733Google Scholar
- MacRobbie, E.A.C. (1981) Ion fluxes in ‘isolated’ guard cells of Commelina communis L. J. Expt. Bot. 32, 545–562Google Scholar
- MacRobbie, E.A.C. (1988) Stomatal guard cells. In: Solute transport in plant cells and tissues, pp. 453–497, Baker, D.A., Hall, J.L., eds. Longman Press, HarlowGoogle Scholar
- MacRobbie, E.A.C. (1992) Calcium and ABA-induced stomatal closure. Proc. R. Soc. Lond. B. Biol. Sci. 338, 5–18Google Scholar
- Marquardt, D. (1963) An algorithm for least-squares estimation of nonlinear parameters. J. Soc. Ind. Appl. Math. 11, 431–441Google Scholar
- Marten, I., Lohse, G., Hedrich, R. (1991) Plant growth hormones control voltage-dependent activity of anion channels in plasma membrane of guard cells. Nature 353, 758–762Google Scholar
- Mathieu, Y., Guern, J., Pean, M., Pasquier, C., Beloeil, J.-C., Lallemand, J.-Y. (1986) Cytoplasmic pH regulation in Acer pseudoplatanus cells. II. Possible mechanisms involved in pH regulation during acid-load. Plant Physiol. 83, 846–852Google Scholar
- McAinsh, M.R., Brownlee, C., Hetherington, A.M. (1990) Abscisic acid-induced elevation of guard cell cytosolic Ca2+ precedes stomatal closure. Nature 343, 186–188Google Scholar
- McAinsh, M.R., Brownlee, C., Hetherington, A.M. (1992) Visualizing changes in cytosolic-free Ca2+ during the response of stomatal guard cells to abscisic acid. Plant Cell 4, 1113–1122Google Scholar
- Moody, W.J., Hagiwara, S. (1982) Block of inward rectification by intracellular H+ in immature oocytes of the starfish Mediaster aequalis. J. Gen. Physiol. 79, 115–130Google Scholar
- Parmar, P. (1991) Polyphosphoinositide metabolism in stomatal guard cells. pp. 1–167. Ph.D. thesis, University of CambridgeGoogle Scholar
- Prod'hom, B., Pietrobon, D., Hess, P. (1987) Direct measurement of proton transfer rates to a group controlling the dihydropyridine-sensitive Ca2+ channel. Nature 329, 243–246Google Scholar
- Raschke, K. (1987) Action of abscisic acid on guard cells. In: Stomatal function, pp. 253–279, Zeiger, E., Farhquar, G.D., Cowan, I.R., eds. Stanford University Press, Stanford, CaliforniaGoogle Scholar
- Rea, P.A. Sanders, D. (1987) Tonoplast energization: two H+ pumps, one membrane. Physiol. Plant. 71, 131–141Google Scholar
- Roos, A., Boron, W.F. (1981) Intracellular pH. Physiol. Rev. 61, 296–434Google Scholar
- Schroeder, J.I., Hagiwara, S. (1989) Cytosolic calcium regulates ion channels in the plasma membrane of Vicia faba guard cells. Nature 338, 427–430Google Scholar
- Schroeder, J.I., Keller, B.U. (1992) Two types of anion channel currents in guard cells with distinct voltage regulation. Proc. Natl. Acad. Sci. USA 89, 5025–5029Google Scholar
- Snaith, P.J., Mansfield, T.A. (1982) Control of the CO2 response of stomata by indol-3ylacetic acid and abscisic acid. J. Expt. Bot. 33, 360–365Google Scholar
- Steigner, W., Köhler, K., Simonis, W., Urbach, W. (1988) Transient cytoplasmic pH changes in correlation with opening of potassium channels in Eremosphaera. J. Exp. Bot. 39, 23–36Google Scholar
- Tarczynski, M.C., Outlaw, W.H.J. (1990) Partial characterization of guard-cell phosphenolpyruvate carboxylase: kinetic datum collection in real time from single-cell activities. Arch. Biochem. Biophys. 280, 153–158Google Scholar
- Taylor, C.W., Richardson, A. (1991) Structure and function of inositol trisphosphate receptors. Pharmac. Ther. 51, 97–137Google Scholar
- Terry, B.R., Findlay, G.P. Tyerman, S.D. (1992) Direct effects of Ca2+-channel blockers on plasma membrane cation channels of Amaranthus tricolor protoplasts. J. Expt. Bot. 43, 1457–1473Google Scholar
- Thiel, G., Blatt, M.R. (1991) The mechanism of ion permeation through K+ channels of stomatal guard cells voltage-dependent block by Na +. J. Plant Physiol. 138, 326–334Google Scholar
- Thiel, G., MacRobbie, E.A.C., Blatt, M.R. (1992) Membrane transport in stomatal guard cells: the importance of voltage control. J. Membr. Biol. 126, 1–18Google Scholar
- Tytgat, J., Nilius, B., Carmeliet, E. (1990) Modulation of the T-type cardiac Ca2+ channel by changes in proton concentration. J. Physiol. 96, 973–990Google Scholar
- Woodhull, A.M. (1973) Ionic blockage of sodium channels in nerve. J. Gen. Physiol. 61, 687–708Google Scholar