Plasma Membrane Depolarization Induced by Abscisic Acid in Arabidopsis Suspension Cells Involves Reduction of Proton Pumping in Addition to Anion Channel Activation, Which Are Both Ca2+ Dependent

Abstract

In Arabidopsis suspension cells a rapid plasma membrane depolarization is triggered by abscisic acid (ABA). Activation of anion channels was shown to be a component leading to this ABA-induced plasma membrane depolarization. Using experiments employing combined voltage clamping, continuous measurement of extracellular pH, we examined whether plasma membrane H 1 -ATPases could also be involved in the depolarization. We found that ABA causes simultaneously cell depolarization and medium alkalinization, the second effect being abolished when ABA is added in the presence of H 1 pump inhibitors. Inhibition of the proton pump by ABA is thus a second component leading to the plasma membrane depolarization. The ABA-induced depolarization is therefore the result of two different processes: activation of anion channels and inhibition of H 1 -ATPases. These two processes are independent because impairing one did not suppress the depolarization. Both processes are however dependent on the [Ca 21 ] cyt increase induced by ABA since increase in [Ca 21 ] cyt enhanced anion channels and impaired H 1 -ATPases.Abscisic acid (ABA) induces the depolarization of the plasma membrane (Thiel et al., 1992). This depolarization has been interpreted as the consequence of the activation of anion channels in stomatal guard cells of Vicia faba (Blatt, 1990;Schroeder and Keller, 1992;Thiel et al., 1992;Ward et al., 1995), Nicotiana benthamiana and Commelina communis (Schwartz et al., 1995;Leonhardt et al., 1999). In addition, we demonstrated that the extracellular perception of ABA in Arabidopsis suspension cells was necessary for the activation of anion channels inducing the plasma membrane depolarization (Ghelis et al., 2000a), and recently we showed that this anion channel stimulation induced by extracellular ABA perception was dependent on phospholipase D activities (Hallouin et al., 2002). In guard cells that are the most studied plant cell model used for the dissection of ABA signaling pathways (Assmann, 1993;Schroeder et al., 2001), two distinct anion channels, rapid anion channels (R-type) and slow anion channels (S-type), were proposed to participate in the plasma membrane depolarization (Schroeder and Keller, 1992;. Both R-type and S-type channels have been suggested to contribute to an initial phase of the depolarization, while maintenance of the depolarized state of the plasma membrane was only attributed to the S-type anion channels (Schroeder and Keller, 1992). The mechanisms by which ABA activates anion channels are not entirely understood . In V. faba guard cells, activation of anion channels by ABA can be observed without variation of the cytoplasm calcium concentration, suggesting that the ABA-induced anion efflux is calcium-independent (Schwarz and Schroeder, 1998). However, numerous data support the calcium dependence of the anion channel activation in response to ABA. Some of the anion channels involved in a long-term plasma membrane depolarization are Ca 21 -sensitive and therefore are activated by an increase in cyto...

Plant Senescence: The Role of Volatile Terpene Compounds (VTCs)

“…Other findings have shown that monoterpenes affect biological membranes by damaging their structure and changing their lipid packing density, resulting in increasing ion permeability and perturbs membrane-bound enzyme function [54]. This is similar to the effect of abscisic acid on Arabidopsis cells leading to abscission [55].…”

Cytosolic abscisic acid activates guard cell anion channels without preceding Ca 2+ signals

“…Here, we focused on the activation of anion channels essential for the ABA-induced depolarization that initiates ion efflux from guard cells, and finally leads to stomatal closure. In addition, deactivation of H ϩ -ATPases may contribute to the depolarization, as was recently shown for suspension cells of Arabidopsis thaliana (43). Although ABA inhibition of H ϩ -ATPases was also reported for guard cells (44), the changes in H ϩ current (45) will be masked by the massive increase in anion channel activity recorded for guard cells in intact plants.…”

A comparison of the effects of 1,4-naphthoquinone and 2-hydroxy-1,4-naphthoquinone (lawsone) on indole-3-acetic acid (IAA)-induced growth of maize coleoptile cells

“…There are many reports in the literature concerning the impairment of the transport ATPases through interactions with ROS either through the direct oxidation of amino acid residues or via the peroxidation of membrane phospholipids (reviewed in Kourie 1998). It is also possible that ROS-induced cytosol Ca 2+ elevations (reviewed in Mori and Schroeder 2004), in turn, can inhibit PM H + -ATPase activity (Brault et al 2004;Kinoshita et al 1995;Polevoi et al 1996), and depolarise plasma membrane potential (Trouverie et al 2008). It can be also speculated that the inhibition of IAA-induced growth may also be caused by an ROS-induced K + efflux, which results in a dramatic K + loss from plant cells (reviewed in Demidchik et al 2014).…”