Effect of d-myo-Inositol 1,4,5-Trisphosphate on the Electrical Properties of the Red Beet Vacuole Membrane

Abstract

The effect of channel opening in the tonoplast by D-myo-inositol 1,4,5-trisphosphate [lns(1,4,5)P3] has been examined on red beet (Beta vulgaris) vacuoles. Patch-clamp measurements of the vacuolar potential and current were performed on vacuoles isolated in 0.1 micromolar free Ca2+ medium. With vacuoles clamped at +30 millivolts, the lns(1,4,5)P3 induced changes in current were depending on the Ca2+ buffer strength in the external medium.The spontaneous depolarization of vacuoles in which H+-pumps were activated by 5 millimolar MgATP was increased from +6 to +18 millivolts by 1 micromolar lns(1,4,5)P3. We have interpreted our data by assuming that even with 2 millimolar EGTA to buffer Ca2+ at 0.1 micromolar in the external medium, lns(1,4,5)P3 released enough Ca2+ from the vacuole to produce an accumulation of this ion near the tonoplast. Apart from their dependency with free Ca2+ in the cytoplasm, the electrical properties of the tonoplast could be depending on the lns(1,4,5)P3 and Ca2+ buffer values in the cytoplasm.is also used in plant cells to increase the free cytoplasmic Ca2l and eventually induce a physiological response by releasing part of the high Ca2" content of the vacuolar reservoir (10-4-10-2 M) (4). However, we have found that less than micromolar concentrations of Ins(1,4,5)P3 were sufficient to open Ca2" channels in the tonoplast (2). The effect of Ins(1,4,5)P3 was reversible and quite specific when compared with other inositides. These studies were performed on vacuoles isolated in nonphysiological high (10-3 M) Ca2" medium, in order to facilitate study of the Ins( 1 ,4,5)P3 opened channels [in the range 0 to +100 mV the background current due to NSC is negligible when compared to the Ins( 1,4,5)P3 induced current].Here we present our results on the effect of Ins ( 1 ,

Intracellular Ca2+ is important for flagellin-triggered defense in Arabidopsis and involves inositol polyphosphate signaling

“…Generation of IP3 during a signaling cascade could lead to the production of IP6 through the action of IPK1 and 2 ( Munnik and Nielsen, 2011 ). Electrophysiological studies employing isolated plant cell vacuoles have shown that application of either IP3 ( Alexandre and Lassalles, 1990 ; Allen and Sanders, 1995 ) or IP6 ( Lemtiri-Chlieh et al , 2003 ) to the cytosolic face of the tonoplast results in outward Ca 2+ currents from the vacuole lumen. Consistent with these patch clamp studies of Ca 2+ currents across the tonoplast, release of caged IP3 ( Lemtiri-Chlieh et al , 2003 ) or IP6 ( Gilroy et al , 1990 ) in intact protoplasts results in cytoplasmic Ca 2+ elevation due to release of Ca 2+ from intracellular stores.…”

Ca 2 + signaling by plant Arabidopsis thaliana Pep peptides depends on AtPepR1, a receptor with guanylyl cyclase activity, and cGMP-activated Ca 2+ channels

“…In these signaling pathways, cytosolic IP3 generation on perception of an external stimulus leads to cytosolic Ca 2+ elevation because of activation of IP3-sensitive tonoplast-localized Ca 2+ channels (30); the resulting cytosolic Ca 2+ spike occurs because of release of intracellular Ca 2+ stores. Using plants in which signal-induced IP3 generation is blocked (31), we found no impairment of AtPep3-mediated cytosolic Ca 2+ elevation; these results suggest that IP3-activated release of vacuolar Ca 2+ does not contribute to AtPep-and AtPepR1-mediated Ca 2+ signaling.…”

The Type B Phosphatidylinositol-4-Phosphate 5-Kinase 3 Is Essential for Root Hair Formation inArabidopsis thaliana

“…Examples for proteins regulated by PtdIns(4,5)P 2 include plant ion channels and ATPases (Cote et al, 1996;Suh and Hille, 2005), plant phospholipase D (Qin et al, 2002), the actin-modifying enzymes profilin, cofilin, and gelsolin (Drobak et al, 1994;Lemmon et al, 2002;Doughman et al, 2003;Wasteneys and Galway, 2003;Wenk and De Camilli, 2004), and mammalian SNARE complex proteins (Vicogne et al, 2006), implying a role for PtdIns(4,5)P 2 in vesicle fusion (Cremona and De Camilli, 2001;Di Paolo et al, 2004;Gong et al, 2005;Milosevic et al, 2005). PtdIns(4,5)P 2 is also the substrate for phospholipase C (PLC), yielding diacylglycerol and the soluble second messenger, inositol 1,4,5-trisphosphate (Berridge, 1983;Meijer and Munnik, 2003), required for Ca 2þ release from internal stores in both animal (Berridge, 1993) and plant cells (Alexandre and Lassalles, 1990;Allen et al, 1995;Sanders et al, 2002). Obviously, regulatory functions described for PtdIns(4,5)P 2 include some of those required for a regulator of growth processes in tip-growing cells.…”