Fast‐activating cation channel in barley mesophyll vacuoles. Inhibition by calcium

Tikhonova, Lioubov I.; Pottosin, Igor; Dietz, Karl‐Josef; Schönknecht, Gerald

doi:10.1046/j.1365-313x.1997.11051059.x

Cited by 63 publications

(69 citation statements)

References 30 publications

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“…2, A and D). This is typical of fast vacuolar (FV) channel activity (26)(27)(28). Addition of 100 nM cADPR to the bath elicited instantaneously activating inward and outward currents that were reversible on cADPR washout (Fig.…”

Section: Guard Cells Are Competent To Respond To Cadprmentioning

confidence: 83%

Abscisic acid-induced stomatal closure mediated by cyclic ADP-ribose

Leckie

McAinsh

Allen

et al. 1998

Proc. Natl. Acad. Sci. U.S.A.

297

224

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Abscisic acid (ABA) is a plant hormone involved in the response of plants to reduced water availability. Reduction of guard cell turgor by ABA diminishes the aperture of the stomatal pore and thereby contributes to the ability of the plant to conserve water during periods of drought. Previous work has demonstrated that cytosolic Ca 2؉ is involved in the signal transduction pathway that mediates the reduction in guard cell turgor elicited by ABA. Here we report that ABA uses a Ca 2؉ -mobilization pathway that involves cyclic adenosine 5-diphosphoribose (cADPR). Microinjection of cADPR into guard cells caused reductions in turgor that were preceded by increases in the concentration of free Ca 2؉ in the cytosol. Patch clamp measurements of isolated guard cell vacuoles revealed the presence of a cADPRelicited Ca 2؉ -selective current that was inhibited at cytosolic Ca 2؉ > 600 nM. Furthermore, microinjection of the cADPR antagonist 8-NH 2 -cADPR caused a reduction in the rate of turgor loss in response to ABA in 54% of cells tested, and nicotinamide, an antagonist of cADPR production, elicited a dose-dependent block of ABA-induced stomatal closure. Our data provide definitive evidence for a physiological role for cADPR and illustrate one mechanism of stimulus-specific Ca 2؉ mobilization in higher plants. Taken Abscisic acid (ABA) is a plant hormone that plays major roles in the control of development and in the response to various environmental stresses. During periods of reduced water availability ABA builds up in the leaves and promotes reductions in the aperture of the stomatal pore. This reduction in stomatal aperture is beneficial to the plant as it serves to reduce the extent of transpirational water loss (1). The reductions in pore width are caused by decreases in the turgor of the two guard cells that surround the stomatal pore. ABA brings about reductions in turgor by promoting the efflux of potassium salt from the guard cells (2). Although it has been known for some time that ABA can operate in guard cells via Ca -permeable channel types on both the plasma membrane and endomembranes, the roles played by these channels in specific signal transduction pathways are unclear (6, 7). Assignment of a particular class or classes of Ca 2ϩ ion channel as response elements in a given stimulus-response coupling pathway is very important in the context of understanding how stimulus-specificity is encoded. This is especially true in the case of the Ca 2ϩ signature because the dynamic properties of the Ca 2ϩ release channels that participate in the response are likely to characterize its spatiotemporal relationships (8).In many animal cells, intracellular Ca 2ϩ mobilization during signaling is achieved by activation of inositol 1,4,5-trisphosphate (InsP 3 ) receptors and͞or ryanodine receptors (9). The Ca 2ϩ -mobilizing properties of InsP 3 in guard cells are established (10), and a recent report has shown that ABA can induce rapid phosphoinositide turnover in guard cells (11). Ca 2ϩ release with the hallmark ch...

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Section: Guard Cells Are Competent To Respond To Cadprmentioning

confidence: 83%

Abscisic acid-induced stomatal closure mediated by cyclic ADP-ribose

Leckie

McAinsh

Allen

et al. 1998

Proc. Natl. Acad. Sci. U.S.A.

297

224

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“…These conductances have been named slow vacuolar (SV), fast vacuolar (FV), and vacuolar K ϩ -selective (VK) channels, with respect to their kinetics, voltage dependency, cation permeability, and sensitivity towards cytosolic Ca 2ϩ (6,7,30,128,328,348). Among the 15 potassium channel sequences identified in the Arabidopsis genome, four twopore K ϩ channels (TPK1, -2, -3, and -5) and a K ir -like one (KCO3) (FIGURE 3A) are not located at the plasma membrane.…”

Section: A Vacuolar Cation Channelsmentioning

confidence: 99%

Ion Channels in Plants

Hedrich

2012

Physiological Reviews

403

322

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Since the first recordings of single potassium channel activities in the plasma membrane of guard cells more than 25 years ago, patch-clamp studies discovered a variety of ion channels in all cell types and plant species under inspection. Their properties differed in a cell type-and cell membranedependent manner. Guard cells, for which the existence of plant potassium channels was initially documented, advanced to a versatile model system for studying plant ion channel structure, function, and physiology. Interestingly, one of the first identified potassium-channel genes encoding the Shaker-type channel KAT1 was shown to be highly expressed in guard cells. KAT1-type channels from Arabidopsis thaliana and its homologs from other species were found to encode the K ϩ -selective inward rectifiers that had already been recorded in early patch-clamp studies with guard cells. Within the genome era, additional Arabidopsis Shaker-type channels appeared. All nine members of the Arabidopsis Shaker family are localized at the plasma membrane, where they either operate as inward rectifiers, outward rectifiers, weak voltage-dependent channels, or electrically silent, but modulatory subunits. The vacuole membrane, in contrast, harbors a set of two-pore K ϩ channels. Just very recently, two plant anion channel families of the SLAC/SLAH and ALMT/QUAC type were identified. SLAC1/SLAH3 and QUAC1 are expressed in guard cells and mediate Slow-and Rapid-type anion currents, respectively, that are involved in volume and turgor regulation. Anion channels in guard cells and other plant cells are key targets within often complex signaling networks. Here, the present knowledge is reviewed for the plant ion channel biology. Special emphasis is drawn to the molecular mechanisms of channel regulation, in the context of model systems and in the light of evolution.

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“…7 and 10). These channels are oppositely regulated by cytosolic Ca 2+ : SV channels are activated and FV channels are efficiently inhibited by micromolar free Ca 2+ (Hedrich and Neher, 1987;Tikhonova et al, 1997). Thus, at resting Ca 2+ conditions, FV channels dominate the tonoplast passive conductance for monovalent cations such as K + , Na + , and NH 4 + .…”

Section: Saline Conditions Reduce the Activity Of The Fv Channel Morementioning

confidence: 99%

“…Single vacuoles were mechanically isolated from mesophyll protoplasts as described by Tikhonova et al (1997). Current measurements were performed using an Axopatch 200B integrating patch-clamp amplifier (Axon Instruments).…”

Section: Patch-clamp Electrophysiologymentioning

confidence: 99%

Reduced Tonoplast Fast-Activating and Slow-Activating Channel Activity Is Essential for Conferring Salinity Tolerance in a Facultative Halophyte, Quinoa

et al. 2013

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Halophyte species implement a "salt-including" strategy, sequestering significant amounts of Na + to cell vacuoles. This requires a reduction of passive Na + leak from the vacuole. In this work, we used quinoa (Chenopodium quinoa) to investigate the ability of halophytes to regulate Na + -permeable slow-activating (SV) and fast-activating (FV) tonoplast channels, linking it with Na + accumulation in mesophyll cells and salt bladders as well as leaf photosynthetic efficiency under salt stress. Our data indicate that young leaves rely on Na + exclusion to salt bladders, whereas old ones, possessing far fewer salt bladders, depend almost exclusively on Na + sequestration to mesophyll vacuoles. Moreover, although old leaves accumulate more Na + , this does not compromise their leaf photochemistry. FV and SV channels are slightly more permeable for K + than for Na + , and vacuoles in young leaves express less FV current and with a density unchanged in plants subjected to high (400 mM NaCl) salinity. In old leaves, with an intrinsically lower density of the FV current, FV channel density decreases about 2-fold in plants grown under high salinity. In contrast, intrinsic activity of SV channels in vacuoles from young leaves is unchanged under salt stress. In vacuoles of old leaves, however, it is 2-and 7-fold lower in older compared with young leaves in control-and saltgrown plants, respectively. We conclude that the negative control of SV and FV tonoplast channel activity in old leaves reduces Na + leak, thus enabling efficient sequestration of Na + to their vacuoles. This enables optimal photosynthetic performance, conferring salinity tolerance in quinoa species.The increasing problem of global land salinization (Flowers, 2004;Rengasamy, 2006) and its associated multibillion dollar losses in agricultural production require a better understanding of the key physiological mechanisms that confer salinity tolerance in crops. One effective way of gaining such knowledge comes from studying halophytes (Glenn et al., 1999;Flowers and Colmer, 2008;Shabala and Mackay, 2011).One of the prominent features of halophytes is their ability to efficiently sequester cytosolically toxic Na + to the cell vacuole. The classic view is that this sequestration is achieved by tonoplast Na + /H + antiporters (Barkla et al., 1995;Flowers and Colmer, 2008), a process energized by both vacuolar H + pumps: ATPase (Ayala et al., 1996;Vera-Estrella et al., 1999;Wang et al., 2001) and pyrophosphatase (Parks et al., 2002;Vera-Estrella et al., 2005;Guo et al., 2006;Krebs et al., 2010). However, recent studies have added more complexity to the relationship between Na + /H + antiporters and vacuolar Na + sequestration, assigning a role to the transporter in the regulation of K + and H + homeostasis (for review, see Rodríguez-Rosales et al., 2009;Jiang et al., 2010; Bassil et al., 2011 (Yamaguchi et al., 2005). Consequently, other transporters, in addition to and different from NHX, are likely to be involved in vacuolar Na + sequestration. In addition...

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Fast‐activating cation channel in barley mesophyll vacuoles. Inhibition by calcium

Cited by 63 publications

References 30 publications

Abscisic acid-induced stomatal closure mediated by cyclic ADP-ribose

Abscisic acid-induced stomatal closure mediated by cyclic ADP-ribose

Ion Channels in Plants

Reduced Tonoplast Fast-Activating and Slow-Activating Channel Activity Is Essential for Conferring Salinity Tolerance in a Facultative Halophyte, Quinoa

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