Substrate Regulation of Single Potassium and Chloride Ion Channels in <i>Arabidopsis</i> Plasma Membrane

Lew, Roger R.

doi:10.1104/pp.95.2.642

Cited by 44 publications

(22 citation statements)

References 16 publications

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“…The presence of potassium channel activity based upon the effect of tetraethylammonium on current-voltage relations is not surprising given a previous report of potassium ion channels in the plasma membrane ofArabidopsis (13). The hyperpolarization caused by tetraethylammonium is clear evidence that the K+ channel does function in the uptake of K+ into the cell.…”

Section: Tip Growth and Ion Fluxesmentioning

confidence: 80%

Electrogenic Transport Properties of Growing Arabidopsis Root Hairs

Lew¹

1991

Plant Physiol.

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Ion transport, measured using double-barreled micropipettes to obtain current-voltage relations, was examined in Arabidopsis thaliana root hairs that continued tip growth and cytoplasmic streaming after impalement with the micropipette. To do this required in situ measurements with no handling of the seedlings to avoid wounding responses, and conditions allowing good resolution microscopy in tandem with the electrophysiological measurements. Two ion transport processes were demonstrated. One was a tetraethylammonium-sensitive potassium ion current, inward at hyperpolarized potentials and outward at depolarized potentials. The addition of tetraethylammonium (a potassium channel blocker) caused the potential to hyperpolarize, indicating the presence of a net inward potassium current through the ion channels at the resting potential. The potassium influx was sufficient to "drive" cellular expansion based upon growth rates. Indeed, tetraethylammonium caused transient inhibition of tip growth. The other electrogenic process was the plasma membrane proton pump, measured by indirect inhibition with cyanide or direct inhibition by vanadate. The proton pump was the dominant contribution to the resting potential, with a very high current density of about 250 microamperes per square centimeter (seen only in young growing root hairs). The membrane potential generated by the proton pump presumably drives the potassium influx required for cellular expansion. The pump appears to be a constant current source over the voltage range -200 to 0 millivolts. With this system, it is now possible to study the physiology of a higher plant cell in dynamic living state using a broad range of cell biological and electrophysiological techniques.

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Section: Tip Growth and Ion Fluxesmentioning

confidence: 80%

Electrogenic Transport Properties of Growing Arabidopsis Root Hairs

Lew¹

1991

Plant Physiol.

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“…50 mmol kg-' plant water, the higher uptake that occurs in stl2 must be associated with a mechanism that can regulate cytoplasmic K+ content. For example, such high uptake may be a transient phenomenon that is feedback regulated by increasing cytoplasmic content or coupled with an effective efflux mechanism (Pettersson 1986;Lew 1991). We measured loss of radiolabeled Rb+ from gametophytes and into unlabeled rinse medium following a 2-h preloading with Rb+ alone.…”

Section: Responsesmentioning

confidence: 99%

The Analysis of Genetically and Physiologically Complex Traits Using Ceratopteris: A Case Study of NaCl-Tolerant Mutants

Warne¹,

Vogelien²,

Hickok³

1995

International Journal of Plant Sciences

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Warne TR, Vogelien DL, Hickok LG. 1995. The analysis of genetically and physiologically complex traits using ceratopteris -a casestudy of nacl-tolerant mutants. Int J Plant Sci 156(3):374-84. Genetic and physiological complexities associated with salt tolerance in plants have limited progress in the analysis of specific factors responsible for the salt-tolerant phenotype. We have used the homosporous fern Ceratopteris richardii as a model plant to investigate the physiological basis of salinity tolerance by selecting single gene mutants that confer tolerance in the gametophyte generation. The unique genetic system of homosporous ferns permits the generation of mutants in a genetic background nearly isogenic to the wildtype, such that comparative studies with the wildtype can identify specific physiological responses associated with salt tolerance. One of these mutations, st12, confers a high level of tolerance to Na+ (I50 175 mM NaCl) and generates a complex suite of related phenotypes. For example, in addition to Na+ tolerance, stl2 exhibits tolerance to Mg2+ salts, sensitivity to supplemented K+, higher K+ -dependent efflux of K+, altered responses to Ca2+ supplementation and moderate tolerance to osmotic stresses. Based upon its physiological attributes, we have proposed that the mechanism of action for this mutation involves an enhanced influx of K+ and higher selectivity for K+ over Na+ in a K+ channel. The direct and indirect consequences of this alteration can account for NaCl tolerance and the other phenotypes evident in st12. The complex set of phenotypic responses from such a single gene mutation illustrates the potential for even more extreme pleiotropy in multigenic salt-tolerant strains.

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“…These limitations are addressed in our development of the HoTSig approach. (Lew et al, 1979;Lew and Bookchin, 1986;Lew, 1991;Gradmann et al, 1993) and others (Loew and Schaff, 2001;Hunter and Nielsen, 2005;Shabala et al, 2006) in providing realtime feedback for the operator as well as a detailed output log. We adapted a number of generalized utilities that greatly reduce computational load and time, notably the Newton-Raphson chord approximation to solutions of implicit equations (Lew and Bookchin, 1986), and we introduced a look-ahead utility to adjust time increments to the pending dynamics of the model (Supplemental Appendices S3 and S4).…”

Section: A Quantitative Modeling Approachmentioning

confidence: 99%

OnGuard, a Computational Platform for Quantitative Kinetic Modeling of Guard Cell Physiology

et al. 2012

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Stomatal guard cells play a key role in gas exchange for photosynthesis while minimizing transpirational water loss from plants by opening and closing the stomatal pore. Foliar gas exchange has long been incorporated into mathematical models, several of which are robust enough to recapitulate transpirational characteristics at the whole-plant and community levels. Few models of stomata have been developed from the bottom up, however, and none are sufficiently generalized to be widely applicable in predicting stomatal behavior at a cellular level. We describe here the construction of computational models for the guard cell, building on the wealth of biophysical and kinetic knowledge available for guard cell transport, signaling, and homeostasis. The OnGuard software was constructed with the HoTSig library to incorporate explicitly all of the fundamental properties for transporters at the plasma membrane and tonoplast, the salient features of osmolite metabolism, and the major controls of cytosolic-free Ca 2+ concentration and pH. The library engenders a structured approach to tier and interrelate computational elements, and the OnGuard software allows ready access to parameters and equations 'on the fly' while enabling the network of components within each model to interact computationally. We show that an OnGuard model readily achieves stability in a set of physiologically sensible baseline or Reference States; we also show the robustness of these Reference States in adjusting to changes in environmental parameters and the activities of major groups of transporters both at the tonoplast and plasma membrane. The following article addresses the predictive power of the OnGuard model to generate unexpected and counterintuitive outputs.Stomatal guard cells surround pores in the epidermis of plant leaves and regulate the pore aperture. They open the pore in response to low CO 2 and light to facilitate CO 2 access for photosynthesis, and they close the pore in the dark, under drought stress, and in the presence of the water-stress hormone abscisic acid to minimize water loss through transpiration. Stomata have a profound impact on the water and carbon cycles of the world (Gedney et al., 2006;Betts et al., 2007). Their dynamics have been incorporated into models for transpiration and water use efficiency (Farquhar and Wong, 1984;Ball, 1987;Williams et al., 1996;Eamus and Shanahan, 2002;West et al., 2005), successfully reproducing the gas exchange, CO 2 , and transpirational characteristics of experiments at the plant and community levels. To date, these models have taken a top-down approach. They subsume stomatal movements within a few empirical parameters of linear hydraulic pathways and conductances without reference to the molecular mechanics of the guard cell. No generalized guard cell model has yet to be developed from the bottom up, drawing on the wealth of knowledge available for guard cell transport, signaling, and homeostasis. It is clear that such a model is now needed. The depth and breadth of information ava...

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Substrate Regulation of Single Potassium and Chloride Ion Channels in Arabidopsis Plasma Membrane

Cited by 44 publications

References 16 publications

Electrogenic Transport Properties of Growing Arabidopsis Root Hairs

Electrogenic Transport Properties of Growing Arabidopsis Root Hairs

The Analysis of Genetically and Physiologically Complex Traits Using Ceratopteris: A Case Study of NaCl-Tolerant Mutants

OnGuard, a Computational Platform for Quantitative Kinetic Modeling of Guard Cell Physiology

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