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Auxin carriers in Cucurbita vesicles

I. Imposed perturbations of transmembrane pH and electrical potential gradients characterised by radioactive probes

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Abstract

The behaviour of radioactive probes of transmembrane pH gradients ([14C]butyric acid) and electrical potential gradients (86Rb+ and S14CN-) has been characterised in membrane vesicles from Cucurbita pepo L. hypocotyls subjected to changing gradients and ionophore-mediated changes in the conductivity of K+ and H+ ions. The vesicles are sealed in the presence of 25 mM KCl. The K+ ionophore valinomycin changes the distribution of 86Rb+ and of S14CN- in opposite directions, which depend on the external K+ concentration. The accumulation of [14C]butyric acid by the vesicles and its association with the membranous phase are enhanced by increasing acidity, as expected for this lipophilic weak acid (pKa=4.8). Uptake of S14CN- increases and valinomycin-stimulated 86Rb+ uptake decreases when the external pH is lowered, indicating a strongly pH-dependent H+ diffusion potential.

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Abbreviations

CCCP:

carbonylcyanide m-chlorophenylhydrazone

FW:

fresh weight

IAA:

indole-3-acetic acid

ION3:

mixture of 4 μM valinomycin CCCP and nigericin

NAA:

1-naphthylacetic acid

NPA:

N-1-naphthylphthalamic acid

VAL:

valinomycin

ΔΨ:

electrical potential difference

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Author notes

  1. M. Sabater

    Present address: Departamento de Biologia Facultad de Biologia, Universidad de Murcia, Espinardo, Murcia, Spain

Authors and Affiliations

  1. Department of Biochemistry, University of Cambridge, CB2 1QW, Cambridge, UK

    M. Sabater & P. H. Rubery

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  1. M. Sabater
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  2. P. H. Rubery
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Sabater, M., Rubery, P.H. Auxin carriers in Cucurbita vesicles. Planta 171, 501–506 (1987). https://doi.org/10.1007/BF00392298

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  • DOI: https://doi.org/10.1007/BF00392298

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