Membrane voltage initiates Ca2+ waves and potentiates Ca2+ increases with abscisic acid in stomatal guard cells.

In higher plants changes and oscillations in cytosolic free Ca2+ concentration ([Ca2+]i) are central to hormonal physiology, including that of abscisic acid (ABA), which signals conditions of water stress and alters ion channel activities in guard cells of higher-plant leaves. Such changes in [Ca2+]i are thought to encode for cellular responses to different stimuli, but their origins and functions are poorly understood. Because transients and oscillations in membrane voltage also occur in guard cells and are elicited by hormones, including ABA, we suspected a coupling of [Ca2+]i to voltage and its interaction with ABA. We recorded [Ca2+]i by Fura2 fluorescence ratio imaging and photometry while bringing membrane voltage under experimental control with a two-electrode voltage clamp in intact Vicia guard cells. Free-running oscillations between voltages near -50 mV and -200 mV were associated with oscillations in [Ca2+]i, and, under voltage clamp, equivalent membrane hyperpolarizations caused [Ca2+]i to increase, often in excess of 1 microM, from resting values near 100 nM. Image analysis showed that the voltage stimulus evoked a wave of high [Ca2+]i that spread centripetally from the peripheral cytoplasm within 5-10 s and relaxed over 40-60 s thereafter. The [Ca2+]i increases showed a voltage threshold near -120 mV and were sensitive to external Ca2+ concentration. Substituting Mn2+ for Ca2+ to quench Fura2 fluorescence showed that membrane hyperpolarization triggered a divalent influx. ABA affected the voltage threshold for the [Ca2+]i rise, its amplitude, and its duration. In turn, membrane voltage determined the ability of ABA to raise [Ca2+]i. These results demonstrate a capacity for voltage to evoke [Ca2+]i increases, they point to a dual interaction with ABA in triggering and propagating [Ca2+]i increases, and they implicate a role for voltage in "conditioning" [Ca2+]i signals that regulate ion channels for stomatal function.

[1]  D. Marquardt.  An Algorithm for Least-Squares Estimation of Nonlinear Parameters , 1963 .

[2]  S. Hagiwara,et al.  Repetitive increases in cytosolic Ca2+ of guard cells by abscisic acid activation of nonselective Ca2+ permeable channels. , 1990, Proceedings of the National Academy of Sciences of the United States of America.

[3]  M. Fricker,et al.  Role of Calcium in Signal Transduction of Commelina Guard Cells. , 1991, The Plant cell.

[4]  H. Sentenac,et al.  pH and Ionic Conditions in the Apoplast , 1991 .

[5]  A. Hetherington,et al.  Visualizing Changes in Cytosolic-Free Ca2+ during the Response of Stomatal Guard Cells to Abscisic Acid. , 1992, The Plant cell.

[6]  Two types of anion channel currents in guard cells with distinct voltage regulation. , 1992, Proceedings of the National Academy of Sciences of the United States of America.

[7]  G. Matthews,et al.  Ca2+ and Mn2+ influx through receptor-mediated activation of nonspecific cation channels in mast cells. , 1993, Proceedings of the National Academy of Sciences of the United States of America.

[8]  M. Blatt,et al.  K+ channels of stomatal guard cells: bimodal control of the K+ inward-rectifier evoked by auxin. , 1994, The Plant journal : for cell and molecular biology.

[9]  M. Lazdunski,et al.  Calcicludine, a venom peptide of the Kunitz-type protease inhibitor family, is a potent blocker of high-threshold Ca2+ channels with a high affinity for L-type channels in cerebellar granule neurons. , 1994, Proceedings of the National Academy of Sciences of the United States of America.

[10]  M. Fricker,et al.  Two Transduction Pathways Mediate Rapid Effects of Abscisic Acid in Commelina Guard Cells. , 1994, The Plant cell.

[11]  Roles of Ion Channels in Initiation of Signal Transduction in Higher Plants. , 1995 .

[12]  D. Sanders,et al.  Calcineurin, a Type 2B Protein Phosphatase, Modulates the Ca2+-Permeable Slow Vacuolar Ion Channel of Stomatal Guard Cells. , 1995, The Plant cell.

[13]  J. Bockaert,et al.  Functional coupling between ryanodine receptors and L-type calcium channels in neurons , 1996, Nature.

[14]  A. Trewavas,et al.  Growth of Pollen Tubes of Papaver rhoeas Is Regulated by a Slow-Moving Calcium Wave Propagated by Inositol 1,4,5-Trisphosphate. , 1996, The Plant cell.

[15]  M. Berridge.  Microdomains and elemental events in calcium signalling. , 1996, Cell calcium.

[16]  D. Ehrhardt,et al.  Calcium Spiking in Plant Root Hairs Responding to Rhizobium Nodulation Signals , 1996, Cell.

[17]  A. Trewavas,et al.  Cold calcium signaling in Arabidopsis involves two cellular pools and a change in calcium signature after acclimation. , 1996, The Plant cell.

[18]  B. Ehrlich,et al.  The inositol 1,4,5-trisphosphate receptor of cerebellum. Mn2+ permeability and regulation by cytosolic Mn2+ , 1996, The Journal of general physiology.

[19]  Jonathan D. G. Jones,et al.  Resistance gene-dependent plant defense responses. , 1996, The Plant cell.

[20]  J. R. Wood,et al.  Spatial Organization of Calcium Signaling Involved in Cell Volume Control in the Fucus Rhizoid. , 1996, The Plant cell.

[21]  M. Berridge,et al.  Subcellular Ca2+ signals underlying waves and graded responses in HeLa cells , 1996, Current Biology.

[22]  A. Campbell,et al.  Calcium imaging shows differential sensitivity to cooling and communication in luminous transgenic plants. , 1996, Cell calcium.

[23]  A. Webb,et al.  Carbon dioxide induces increases in guard cell cytosolic free calcium , 1996 .

[24]  P. K. Hepler,et al.  POLLEN GERMINATION AND TUBE GROWTH. , 1997, Annual review of plant physiology and plant molecular biology.

[25]  M. Blatt,et al.  Signalling gates in abscisic acid‐mediated control of guard cell ion channels , 1997 .

[26]  E. Blumwald,et al.  Hyperpolarization-activated Ca2+-permeable Channels in the Plasma Membrane of Tomato Cells , 1997, The Journal of Membrane Biology.

[27]  S. A. Barnes,et al.  Light signal transduction in plants. , 1997, Trends in cell biology.

[28]  Colin Brownlee,et al.  Calcium ions as second messengers in guard cell signal transduction , 1997 .