Effects of Nppb and Niflumic Acid on Outward K+ and Cl- Currents Across the Plasma Membrane of Wheat Root Protoplasts

Garrill, Ashley; Tyerman, SD; Findlay, G. P.; Ryan, PR

doi:10.1071/pp9960527

Cited by 26 publications

(13 citation statements)

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“…Reversal potentials were also obtained by subtracting the I-V curves before and after addition of niflumate or DPC in 10 mm external TEACl and assuming that the anion current was the only electrogenic transport inhibited by these compounds. Outward K ϩ channels are blocked by niflumate (Garrill et al, 1996), but in the present experiments TEA ϩ was the only cation in the pipette solution. When the average reversal potential of the net currents (45 Ϯ 12 mV, n ϭ 6) was used the P mal 2Ϫ /P Cl Ϫ is 2.6.…”

Section: Al 3؉ -Activated Inward Current Carried By Malate Effluxmentioning

confidence: 85%

Malate-Permeable Channels and Cation Channels Activated by Aluminum in the Apical Cells of Wheat Roots

2001

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Aluminum (Al 3ϩ )-dependent efflux of malate from root apices is a mechanism for Al 3ϩ tolerance in wheat (Triticum aestivum). The malate anions protect the sensitive root tips by chelating the toxic Al 3ϩ cations in the rhizosphere to form non-toxic complexes. Activation of malate-permeable channels in the plasma membrane could be critical in regulating this malate efflux. We examined this by investigating Al 3ϩ -activated channels in protoplasts from root apices of near-isogenic wheat differing in Al 3ϩ tolerance at a single locus. Using whole-cell patch clamp we found that Al 3ϩ stimulated an electrical current carried by anion efflux across the plasma membrane in the Al 3ϩ -tolerant (ET8) and Al 3ϩ -sensitive (ES8) genotypes. This current occurred more frequently, had a greater current density, and remained active for longer in ET8 protoplasts than for ES8 protoplasts. The Al 3ϩ -activated current exhibited higher permeability to malate 2Ϫ than to Cl Ϫ (P mal /P Cl Ն 2.6) and was inhibited by anion channel antagonists, niflumate and diphenylamine-2-carboxylic acid. In ET8, but not ES8, protoplasts an outward-rectifying K ϩ current was activated in the presence of Al 3ϩ when cAMP was included in the pipette solution. These findings provide evidence that the difference in Al 3ϩ -induced malate efflux between Al 3ϩ -tolerant and Al 3ϩ -sensitive genotypes lies in the differing capacity for Al 3ϩ to activate malate permeable channels and cation channels for sustained malate release.

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Section: Al 3؉ -Activated Inward Current Carried By Malate Effluxmentioning

confidence: 85%

Malate-Permeable Channels and Cation Channels Activated by Aluminum in the Apical Cells of Wheat Roots

2001

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“…In fact, examples of nonspecific inhibition of plant ion channels by molecules developed to block animal ion channels have already been described. Antagonists of animal L-type Ca2+ channels are potent inhibitors of plant K+-outward rectifiers (Terry et al, 1992;Thomine et al, 1994), and, more recently, anion-channel blockers have been shown to interact with plant K+-outward rectifiers (Garrill et al, 1996). An alternative explanation for the variety of effects of anionchannel blockers is that it reveals the existence of a variety of anion channels exhibiting distinct pharmacological profiles and controlling various developmental responses of the plant.…”

Section: Anion-channel Inhibitionmentioning

confidence: 99%

Anion-Channel Blockers Interfere with Auxin Responses in Dark-Grown Arabidopsis Hypocotyls

et al. 1997

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Anion channels are thought to participate in signal transduction and turgor regulation in higher plant cells. l h e regulation of hypocotyl cell elongation is a situation in which these channels could play important roles because it involves ionic fluxes that are implicated in turgor control and orchestrated by various signals. We have used a pharmacological approach to reveal the contribution of anion channeis in the regulation of the development of hypocotyls by auxins. Auxins induce an inhibition of elongation, a disintegration of the cortical cell layers, and the formation of adventitious roots on Arabidopsis thaliana hypocotyls grown in the dark. Anionchannel blockers such as anthracene-9-carboxylic acid, 4,4'-diisothiocyanatostilbene-2-2'-disulfonic acid, 4-acetamido-4'4~0-thiocyanato-stilbene-2-2'-disulfonic acid, and R(+)-methylindazone; indanyloxyacteic acid-94, which produce little or no stimulation of hypocotyl elongation by themselves, are able to counteract the inhibition and the disintegration induced by auxins with various efficiencies. This interference appears to be specific for auxins and does not occur when hypocotyl elongation is inhibited by other growth regulators such as ethylene or cytokinins. l h e putative involvement of anion channels in auxin signal transduction is discussed.

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“…Outward currents (i.e. anion influx) have been reported in cells of the root cortex in wheat (Garrill et al, 1996;Skerrett and Tyerman, 1994) and maize (Piñ eros and Kochian, 2001;Piñ eros et al, 2002), as well as in root epidermal cells in Arabidopsis (Diatloff et al, 2004). Likewise, channels mediating inward currents (i.e.…”

Section: +mentioning

confidence: 99%

Not all ALMT1‐type transporters mediate aluminum‐activated organic acid responses: the case of ZmALMT1 – an anion‐selective transporter

et al. 2007

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SummaryThe phytotoxic effects of aluminum (Al) on root systems of crop plants constitute a major agricultural problem in many areas of the world. Root exudation of Al-chelating molecules such as low-molecular-weight organic acids has been shown to be an important mechanism of plant Al tolerance/resistance. Differences observed in the physiology and electrophysiology of root function for two maize genotypes with contrasting Al tolerance revealed an association between rates of Al-activated root organic acid release and Al tolerance. Using these genotypes, we cloned ZmALMT1, a maize gene homologous to the wheat ALMT1 and Arabidopsis AtALMT1 genes that have recently been described as encoding functional, Al-activated transporters that play a role in tolerance by mediating Al-activated organic acid exudation in roots. The ZmALMT1 cDNA encodes a 451 amino acid protein containing six transmembrane helices. Transient expression of a ZmALMT1::GFP chimera confirmed that the protein is targeted to the plant cell plasma membrane. We addressed whether ZmALMT1 might underlie the Al-resistance response (i.e. Al-activated citrate exudation) observed in the roots of the Al-tolerant genotype. The physiological, gene expression and functional data from this study confirm that ZmALMT1 is a plasma membrane transporter that is capable of mediating elective anion efflux and influx. However, gene expression data as well as biophysical transport characteristics obtained from Xenopus oocytes expressing ZmALMT1 indicate that this transporter is implicated in the selective transport of anions involved in mineral nutrition and ion homeostasis processes, rather than mediating a specific Al-activated citrate exudation response at the rhizosphere of maize roots.

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Effects of Nppb and Niflumic Acid on Outward K+ and Cl- Currents Across the Plasma Membrane of Wheat Root Protoplasts

Cited by 26 publications

References 0 publications

Malate-Permeable Channels and Cation Channels Activated by Aluminum in the Apical Cells of Wheat Roots

Malate-Permeable Channels and Cation Channels Activated by Aluminum in the Apical Cells of Wheat Roots

Anion-Channel Blockers Interfere with Auxin Responses in Dark-Grown Arabidopsis Hypocotyls

Not all ALMT1‐type transporters mediate aluminum‐activated organic acid responses: the case of ZmALMT1 – an anion‐selective transporter

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