Potassium Fluxes in Chlamydomonas reinhardtii (I.Kinetics and Electrical Potentials)

Malhotra, Bhupinder; Glass, Anthony D. M.

doi:10.1104/pp.108.4.1527

Cited by 32 publications

(23 citation statements)

References 51 publications

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“…Therefore, the independence of the flagellar current delay time on the external K+ indicates that V , does not decrease significantly in this range of K+ concentrations. This conclusion is consistent with the results of V , estima- tion by measuring the equilibrium distribution of lipophilic cations in C. reinhardfii cells (Malhotra and Glass, 1995a).…”

Section: Desensitization Of the Photoreceptor Current Is Not Limited supporting

confidence: 82%

“…At the crossover point concentration of 0.6 mM, no net K+ flux occurs. This equilibrium value of external K+ concentration is higher than the value yielding a zero driving force for K+ in C. reinhardtii cells at rest (0.3 mM; Malhotra and Glass, 1995a). This difference could be expected, taking into account depolarization of the cell by the photoreceptor and flagellar currents before triggering the K+ fluxes.…”

Section: Desensitization Of the Photoreceptor Current Is Not Limited mentioning

confidence: 78%

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Desensitization and Dark Recovery of the Photoreceptor Current in Chlamydomonas reinhardtii

1997

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Photoexcitation of rhodopsin in Chlamydomonas reinhardtii triggers a complex of rapid bioelectric processes in the cell membrane. Photoreceptor and flagellar currents are the major components of this cascade and are the basis for the phototaxis and photoshock response, respectively. Desensitization and dark recovery of the extracellularly recorded photoreceptor current were investigated in double-flash excitation experiments. l h e data obtained show that the desensitization is determined by membrane depolarization rather than by rhodopsin bleaching. At external K+ concentrations less than 0.6 mM, generation of the flagellar current triggers a transient, depolarization-activated K+ efflux that contributes to membrane repolarization after light excitation. Acceleration of the dark recovery at 5 to 10 mM Ca2+ can be partially attributed to a blockade of K+ influx, which is triggered at higher external K+ concentrations. K+ currents constitute a nove1 component of the rhodopsin-mediated signaling system in C. reinhardtii that is involved in the process of dark adaptation of the system.

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Section: Desensitization Of the Photoreceptor Current Is Not Limited supporting

confidence: 82%

Section: Desensitization Of the Photoreceptor Current Is Not Limited mentioning

confidence: 78%

Desensitization and Dark Recovery of the Photoreceptor Current in Chlamydomonas reinhardtii

1997

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“…This means that the membrane voltage is higher (less negative) at more acidic pH (Malhotra and Glass, 1995) and that an increase in passive ion conductance will cause a depolarization under most circumstances. This is exactly what happens when CHR1 is illuminated, regardless of which cation species is available.…”

Section: Discussionmentioning

confidence: 99%

Channelrhodopsin-1 Initiates Phototaxis and Photophobic Responses inChlamydomonasby Immediate Light-Induced Depolarization

et al. 2008

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Channelrhodopsins (CHR1 and CHR2) are light-gated ion channels acting as sensory photoreceptors in Chlamydomonas reinhardtii. In neuroscience, they are used to trigger action potentials by light in neuronal cells, tissues, or living animals. Here, we demonstrate that Chlamydomonas cells with low CHR2 content exhibit photophobic and phototactic responses that strictly depend on the availability of CHR1. Since CHR1 was described as a H þ -channel, the ion specificity of CHR1 was reinvestigated in Xenopus laevis oocytes. Our experiments show that, in addition to H þ , CHR1 also conducts Na þ , K þ , and Ca 2þ . The kinetic selectivity analysis demonstrates that H þ selectivity is not due to specific translocation but due to selective ion binding. Purified recombinant CHR1 consists of two isoforms with different absorption maxima, CHR1 505 and CHR1 463 , that are in pH-dependent equilibrium. Thus, CHR1 is a photochromic and protochromic sensory photoreceptor that functions as a light-activated cation channel mediating phototactic and photophobic responses via depolarizing currents in a wide range of ionic conditions.

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“…1, A, C, and E). Typically, the HATS is reported to be more sensitive to metabolic inhibitors compared with the LATS (Malhotra and Glass, 1995) , Glu, and DEPC had no effect on K + influx (Fig. 1, B, D, and F; Essah et al, 2003).…”

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confidence: 94%

Capacity and Plasticity of Potassium Channels and High-Affinity Transporters in Roots of Barley and Arabidopsis

Coskun

Britto

et al. 2013

Plant Physiology

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The role of potassium (K + ) transporters in high-and low-affinity K + uptake was examined in roots of intact barley (Hordeum vulgare) ] ext , among the highest transporter-mediated K + fluxes hitherto reported. This ammonium-withdrawal effect was also established in all Arabidopsis lines (the wild types, atakt1, athak5, and athak5 atakt1) at low [K + ] ext , revealing the concerted involvement of several transport systems. The ammoniumwithdrawal effect coincided with a suppression of K + efflux and a significant hyperpolarization of the plasma membrane in all genotypes except athak5 atakt1, could be sustained over 24 h, and resulted in increased tissue K + accumulation. We discuss key differences and similarities in K + acquisition between two important model systems and reveal novel aspects of K + transport in planta.

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Potassium Fluxes in Chlamydomonas reinhardtii (I.Kinetics and Electrical Potentials)

Cited by 32 publications

References 51 publications

Desensitization and Dark Recovery of the Photoreceptor Current in Chlamydomonas reinhardtii

Desensitization and Dark Recovery of the Photoreceptor Current in Chlamydomonas reinhardtii

Channelrhodopsin-1 Initiates Phototaxis and Photophobic Responses inChlamydomonasby Immediate Light-Induced Depolarization

Capacity and Plasticity of Potassium Channels and High-Affinity Transporters in Roots of Barley and Arabidopsis

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