Open AccessTransport of Gibberellin A1 in Cowpea Membrane Vesicles
Author(s) -
Sharman D. O’Neill,
Brian Keith,
Lawrence Rappaport
Publication year - 1986
Publication title -
plant physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.554
H-Index - 312
eISSN - 1532-2548
pISSN - 0032-0889
DOI - 10.1104/pp.80.4.812
Subject(s) - vesicle , chemistry , membrane , biophysics , acridine orange , atpase , membrane transport , intracellular , biochemistry , quenching (fluorescence) , vacuole , gibberellin , membrane permeability , fluorescence , biology , botany , apoptosis , physics , quantum mechanics , cytoplasm , enzyme
The permeability properties of gibberellin A(1) (GA(1)) were examined in membrane vesicles isolated from cowpea hypocotyls. The rate of GA(1) uptake was progressively greater as pH decreased, indicating that the neutral molecule is more permeable than anionic GA(1). Membrane vesicles used in this study possessed a tonoplast-type H(+)-translocating ATPase as assayed by MgATP-dependent quenching of acridine orange fluorescence and methylamine uptake. However, GA(1) uptake was not stimulated by MgATP. At concentrations in excess of 1 micromolar, GA(1), GA(5), and GA, collapsed both MgATP-generated and artifically imposed pH gradients, apparently by shuttling H(+) across the membrane as neutral GA. The relatively high permeability of neutral GA and the potentially detrimental effects of GA in uncoupling pH gradients across intracellular membranes supports the view that GA(1) accumulation and compartmentation must occur by conversion of GA(1) to more polar metabolites.