Abscisic acid regulation of guard-cell K+ and anion channels in Gβ- and RGS-deficient Arabidopsis lines

Liu Min Fan, Wei Zhang, Jin Gui Chen, J. Philip Taylor, Alan M. Jones, Sarah M. Assmann

Research output: Contribution to journalArticle

88 Citations (Scopus)

Abstract

In mammals, basal currents through G protein-coupled inwardly rectifying K+ (GIRK) channels are repressed by Gαi/oGDP, and the channels are activated by direct binding of free Gβγ subunits released upon stimulation of Gαi/o-coupled receptors. However, essentially all information on G protein regulation of GIRK electrophysiology has been gained on the basis of coexpression studies in heterologous systems. A major advantage of the model organism, Arabidopsis thaliana, is the ease with which knockout mutants can be obtained. We evaluated plants harboring mutations in the sole Arabidopsis Gα (AtGPA1), Gβ (AGB1), and Regulator of G protein Signaling (AtRGS1) genes for impacts on ion channel regulation. In guard cells, where K+ fluxes are integral to cellular regulation of stomatal apertures, inhibition of inward K+ (Kin) currents and stomatal opening by the phytohormone abscisic acid (ABA) was equally impaired in Atgpa1 and agb1 single mutants and the Atgpa1 agb1 double mutant. AGB1 overexpressing lines maintained a wild-type phenotype. The Atrgs1 mutation did not affect Kin current magnitude or ABA sensitivity, but K in voltage-activation kinetics were altered. Thus, Arabidopsis cells differ from mammalian cells in that they uniquely use the Gα subunit or regulation of the heterotrimer to mediate Kin channel modulation after ligand perception. In contrast, outwardly rectifying (Kout) currents were unaltered in the mutants, and ABA activation of slow anion currents was conditionally disrupted in conjunction with cytosolic pH clamp. Our studies highlight unique aspects of ion channel regulation by heterotrimeric G proteins and relate these aspects to stomatal aperture control, a key determinant of plant biomass acquisition and drought tolerance.

Original languageEnglish (US)
Pages (from-to)8476-8481
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume105
Issue number24
DOIs
StatePublished - Jun 17 2008

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Abscisic Acid
GTP-Binding Proteins
Arabidopsis
Anions
Ion Channels
GTP-Binding Protein Regulators
Inwardly Rectifying Potassium Channel
Heterotrimeric GTP-Binding Proteins
Mutation
Plant Growth Regulators
Electrophysiology
Droughts
Biomass
Mammals
Ligands
Phenotype
Genes

All Science Journal Classification (ASJC) codes

  • General

Cite this

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title = "Abscisic acid regulation of guard-cell K+ and anion channels in Gβ- and RGS-deficient Arabidopsis lines",
abstract = "In mammals, basal currents through G protein-coupled inwardly rectifying K+ (GIRK) channels are repressed by Gαi/oGDP, and the channels are activated by direct binding of free Gβγ subunits released upon stimulation of Gαi/o-coupled receptors. However, essentially all information on G protein regulation of GIRK electrophysiology has been gained on the basis of coexpression studies in heterologous systems. A major advantage of the model organism, Arabidopsis thaliana, is the ease with which knockout mutants can be obtained. We evaluated plants harboring mutations in the sole Arabidopsis Gα (AtGPA1), Gβ (AGB1), and Regulator of G protein Signaling (AtRGS1) genes for impacts on ion channel regulation. In guard cells, where K+ fluxes are integral to cellular regulation of stomatal apertures, inhibition of inward K+ (Kin) currents and stomatal opening by the phytohormone abscisic acid (ABA) was equally impaired in Atgpa1 and agb1 single mutants and the Atgpa1 agb1 double mutant. AGB1 overexpressing lines maintained a wild-type phenotype. The Atrgs1 mutation did not affect Kin current magnitude or ABA sensitivity, but K in voltage-activation kinetics were altered. Thus, Arabidopsis cells differ from mammalian cells in that they uniquely use the Gα subunit or regulation of the heterotrimer to mediate Kin channel modulation after ligand perception. In contrast, outwardly rectifying (Kout) currents were unaltered in the mutants, and ABA activation of slow anion currents was conditionally disrupted in conjunction with cytosolic pH clamp. Our studies highlight unique aspects of ion channel regulation by heterotrimeric G proteins and relate these aspects to stomatal aperture control, a key determinant of plant biomass acquisition and drought tolerance.",
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Abscisic acid regulation of guard-cell K+ and anion channels in Gβ- and RGS-deficient Arabidopsis lines. / Fan, Liu Min; Zhang, Wei; Chen, Jin Gui; Taylor, J. Philip; Jones, Alan M.; Assmann, Sarah M.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 105, No. 24, 17.06.2008, p. 8476-8481.

Research output: Contribution to journalArticle

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T1 - Abscisic acid regulation of guard-cell K+ and anion channels in Gβ- and RGS-deficient Arabidopsis lines

AU - Fan, Liu Min

AU - Zhang, Wei

AU - Chen, Jin Gui

AU - Taylor, J. Philip

AU - Jones, Alan M.

AU - Assmann, Sarah M.

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N2 - In mammals, basal currents through G protein-coupled inwardly rectifying K+ (GIRK) channels are repressed by Gαi/oGDP, and the channels are activated by direct binding of free Gβγ subunits released upon stimulation of Gαi/o-coupled receptors. However, essentially all information on G protein regulation of GIRK electrophysiology has been gained on the basis of coexpression studies in heterologous systems. A major advantage of the model organism, Arabidopsis thaliana, is the ease with which knockout mutants can be obtained. We evaluated plants harboring mutations in the sole Arabidopsis Gα (AtGPA1), Gβ (AGB1), and Regulator of G protein Signaling (AtRGS1) genes for impacts on ion channel regulation. In guard cells, where K+ fluxes are integral to cellular regulation of stomatal apertures, inhibition of inward K+ (Kin) currents and stomatal opening by the phytohormone abscisic acid (ABA) was equally impaired in Atgpa1 and agb1 single mutants and the Atgpa1 agb1 double mutant. AGB1 overexpressing lines maintained a wild-type phenotype. The Atrgs1 mutation did not affect Kin current magnitude or ABA sensitivity, but K in voltage-activation kinetics were altered. Thus, Arabidopsis cells differ from mammalian cells in that they uniquely use the Gα subunit or regulation of the heterotrimer to mediate Kin channel modulation after ligand perception. In contrast, outwardly rectifying (Kout) currents were unaltered in the mutants, and ABA activation of slow anion currents was conditionally disrupted in conjunction with cytosolic pH clamp. Our studies highlight unique aspects of ion channel regulation by heterotrimeric G proteins and relate these aspects to stomatal aperture control, a key determinant of plant biomass acquisition and drought tolerance.

AB - In mammals, basal currents through G protein-coupled inwardly rectifying K+ (GIRK) channels are repressed by Gαi/oGDP, and the channels are activated by direct binding of free Gβγ subunits released upon stimulation of Gαi/o-coupled receptors. However, essentially all information on G protein regulation of GIRK electrophysiology has been gained on the basis of coexpression studies in heterologous systems. A major advantage of the model organism, Arabidopsis thaliana, is the ease with which knockout mutants can be obtained. We evaluated plants harboring mutations in the sole Arabidopsis Gα (AtGPA1), Gβ (AGB1), and Regulator of G protein Signaling (AtRGS1) genes for impacts on ion channel regulation. In guard cells, where K+ fluxes are integral to cellular regulation of stomatal apertures, inhibition of inward K+ (Kin) currents and stomatal opening by the phytohormone abscisic acid (ABA) was equally impaired in Atgpa1 and agb1 single mutants and the Atgpa1 agb1 double mutant. AGB1 overexpressing lines maintained a wild-type phenotype. The Atrgs1 mutation did not affect Kin current magnitude or ABA sensitivity, but K in voltage-activation kinetics were altered. Thus, Arabidopsis cells differ from mammalian cells in that they uniquely use the Gα subunit or regulation of the heterotrimer to mediate Kin channel modulation after ligand perception. In contrast, outwardly rectifying (Kout) currents were unaltered in the mutants, and ABA activation of slow anion currents was conditionally disrupted in conjunction with cytosolic pH clamp. Our studies highlight unique aspects of ion channel regulation by heterotrimeric G proteins and relate these aspects to stomatal aperture control, a key determinant of plant biomass acquisition and drought tolerance.

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