pH control of the plant outwardly‐rectifying potassium channel SKOR

Lacombe, Benoı̂t; Pilot, Guillaume; Gaymard, Frédéric; Sentenac, Hervé; Thibaud, Jean‐Baptiste

doi:10.1016/s0014-5793(00)01093-0

Cited by 79 publications

(63 citation statements)

References 44 publications

(56 reference statements)

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“…At the molecular level, two Shaker channels are expressed in the pollen tube; SPIK and SKOR are sensitive to external acidification. Whereas SPIK is activated (Mouline et al, 2002), SKOR is inhibited by external protons (Lacombe et al, 2000). Moreover, the SKOR channel is also inhibited by internal acidification (Lacombe et al, 2000).…”

Section: Phmentioning

confidence: 99%

See 1 more Smart Citation

The role of ion fluxes in polarized cell growth and morphogenesis: the pollen tube as an experimental paradigm

Michard¹,

Alves²,

Feijó³

2009

Int. J. Dev. Biol.

118

111

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In order to cope with reproduction in a dry environment without any sort of motility, plants have developed a very specialized and unique sexual system. Of special notice, the two sperm cells that will perform the double fertilization typical of higher plants are carried by one of the fastest growing cells in nature, the pollen tube. This tube develops from the vegetative cell of the pollen grain upon germination on the female tissues. While it cannot be considered as a canonical excitable cell, pollen tubes depend for most of their fundamental functional features on a close regulation of ion dynamics, namely in terms of polarization of extracellular fluxes and formation of standing cytosolic free ion gradients, namely of calcium (Ca 2+ ) and protons (H + ). In turn, these imply that plasma membrane transporters are polarized, or polarly regulated, and that internal signaling cascades transduce this spatial information into the basic features of growth and morphogenesis needed for pollen tubes to target correctly the ovules and discharge the sperm cells. Because of the singularity of this organization, and the ease with which pollen tubes can be experimentally handled, recent years have witnessed an accumulation of data at many levels, from basic biophysical and cell biology characterization, to gene assignment and transcriptomic description of pollen development. In this review we aim to organize this information in terms of the basic biophysical features of membrane function and integrate it into conceptual testable hypotheses on how the dynamics of ion regulation may underlie fundamental properties of cell development.

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Section: Phmentioning

confidence: 99%

“…Whereas SPIK is activated (Mouline et al, 2002), SKOR is inhibited by external protons (Lacombe et al, 2000). Moreover, the SKOR channel is also inhibited by internal acidification (Lacombe et al, 2000). In contrast, the At TPK4 channel, also involved in the pollen tube K + conductance, is blocked by an internal acidification .…”

Section: Phmentioning

confidence: 99%

The role of ion fluxes in polarized cell growth and morphogenesis: the pollen tube as an experimental paradigm

Michard¹,

Alves²,

Feijó³

2009

Int. J. Dev. Biol.

118

111

View full text Add to dashboard Cite

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“…5, in which the medium was buffered with MES-NaOH (pH 6.0) was continuously perfused through the chamber. For patch clamp experiments, cellattached patch recordings were performed on devitellinized oocytes based on methods previously described (56). Voltagepulse protocol application, data acquisition, and data analysis were performed using pClamp software version 9.0 (Axon Instruments) and Sigmaplot software (Jandel Scientific).…”

Section: Expression In Xenopus Oocytes and Electrophysiology-mentioning

confidence: 99%

Increased Functional Diversity of Plant K+ Channels by Preferential Heteromerization of the Shaker-like Subunits AKT2 and KAT2

Xicluna

Lacombe²,

Drèyer³

et al. 2007

Journal of Biological Chemistry

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Assembly of plant Shaker subunits as heterotetramers, increasing channel functional diversity, has been reported. Here we focus on a new interaction, between AKT2 and KAT2 subunits. The assembly as AKT2/KAT2 heterotetramers is demonstrated by (i) a strong signal in two-hybrid tests with intracytoplasmic C-terminal regions, (ii) the effect of KAT2 on AKT2 subunit targeting in tobacco cells, (iii) the complete inhibition of AKT2 currents by co-expression with a dominant-negative KAT2 subunit in Xenopus oocytes, and reciprocally, and (iv) the appearance, upon co-expression of wild-type AKT2 and KAT2 subunits, of new channel functional properties that cannot be explained by the co-existence of two kinds of homotetrameric channels. In particular, the instantaneous current, characteristic of AKT2, displayed new functional features when compared with those of AKT2 homotetramers: activation by external acidification (instead of inhibition) and weak inhibition by calcium. Single channel current measurements in oocytes co-expressing AKT2 and KAT2 revealed a strong preference for incorporation of subunits into heteromultimers and a diversity of individual channels. In planta, these new channels, which may undergo specific regulations, are likely to be formed in guard cells and in the phloem, where they could participate in the control of membrane potential and potassium fluxes.

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“…For oocyte single-channel recordings, oocytes were peeled with tweezers and analyzed by patch clamp according to Ref. 40. The pipette solution contained 100 mM KCl, 3 mM MgCl 2 , 5 mM EGTA, and 10 mM Hepes-NaOH (pH 7.2).…”

Section: Methodsmentioning

confidence: 99%

“…Previous studies have shown that GORK and its SKOR (stelar K ϩ outward rectifier) homolog are sensitive to different signaling factors, such as reactive oxygen species (31,36,37), external K ϩ (26,38,39), and internal and external pH (38,40), and that clustering of GORK channels is correlated with changes in its gating properties (41). Regarding PP2Cs, early physiological studies in guard cells of Nicotiana benthamiana provided evidence that outward K ϩ fluxes were not driven only by depolarization and that PP2C phosphatases could take part in their control.…”

mentioning

confidence: 99%

The Arabidopsis AtPP2CA Protein Phosphatase Inhibits the GORK K+ Efflux Channel and Exerts a Dominant Suppressive Effect on Phosphomimetic-activating Mutations

Lefoulon

Boeglin

Moreau

et al. 2016

Journal of Biological Chemistry

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The regulation of the GORK (Guard Cell Outward Rectifying) Shaker channel mediating a massive K ؉ efflux in Arabidopsis guard cells by the phosphatase AtPP2CA was investigated. Unlike the gork mutant, the atpp2ca mutants displayed a phenotype of reduced transpiration. We found that AtPP2CA interacts physically with GORK and inhibits GORK activity in Xenopus oocytes. Several amino acid substitutions in the AtPP2CA active site, including the dominant interfering G145D mutation, disrupted the GORK-AtPP2CA interaction, meaning that the native conformation of the AtPP2CA active site is required for the GORKAtPP2CA interaction. Furthermore, two serines in the GORK ankyrin domain that mimic phosphorylation (Ser to Glu) or dephosphorylation (Ser to Ala) were mutated. Mutations mimicking phosphorylation led to a significant increase in GORK activity, whereas mutations mimicking dephosphorylation had no effect on GORK. In Xenopus oocytes, the interaction of AtPP2CA with "phosphorylated" or "dephosphorylated" GORK systematically led to inhibition of the channel to the same baseline level. Single-channel recordings indicated that the GORK S722E mutation increases the open probability of the channel in the absence, but not in the presence, of AtPP2CA. The dephosphorylation-independent inactivation mechanism of GORK by AtPP2CA is discussed in relation with well known conformational changes in animal Shaker-like channels that lead to channel opening and closing. In plants, PP2C activity would control the stomatal aperture by regulating both GORK and SLAC1, the two main channels required for stomatal closure.The plant clade A protein phosphatases 2C (PP2Cs) 5 are Mg 2ϩ -and Mn 2ϩ -dependent serine/threonine phosphatases that were first identified as components of the abscisic acid (ABA) signal transduction pathway (1, 2). The clade A APP2C members in Arabidopsis are mostly known as negative regulators of ABA signaling (3). Among this clade, ABI1, ABI2 (4), HAB1 (5), and AtPP2CA (6 -8) are well characterized. These proteins are involved in ABA-regulated germination (7-10). Of these, the ABI1, ABI2, and AtPP2CA genes are highly induced by ABA in guard cells (5). The abi1, abi2, atpp2ca, and hab1 mutants exhibit stomatal phenotypes (1, 4, 5). In particular, the atpp2ca-1 mutant displays impaired control of the stomatal aperture in epidermal strips in response to ABA (7). The role of clade A PP2Cs in stomatal closure in response to ABA has been discovered recently (reviewed in Refs. 11,12). Briefly, the Pyrabactin resistance (PYR)/PYR1-like (PYL)/regulatory component of the ABA receptor (RCAR)-soluble ABA receptors undergo a conformational change upon binding ABA, allowing them to bind and inactivate PP2Cs (13-15) and release the SnRK2.6/OST1 kinase. Without ABA, PP2Cs can bind to OST1 and inactivate it (16, 17). Active OST1 mediates anion efflux through the activation of SLAC1 (18,19). This signaling pathway is important for guard cell plasma membrane depolarization, which drives K ϩ efflux and causes stomatal closure. Besides OST...

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pH control of the plant outwardly‐rectifying potassium channel SKOR

Cited by 79 publications

References 44 publications

The role of ion fluxes in polarized cell growth and morphogenesis: the pollen tube as an experimental paradigm

The role of ion fluxes in polarized cell growth and morphogenesis: the pollen tube as an experimental paradigm

Increased Functional Diversity of Plant K+ Channels by Preferential Heteromerization of the Shaker-like Subunits AKT2 and KAT2

The Arabidopsis AtPP2CA Protein Phosphatase Inhibits the GORK K+ Efflux Channel and Exerts a Dominant Suppressive Effect on Phosphomimetic-activating Mutations

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