Department of Vegetable Crops, University of California, Davis, California 95616.
Plant Physiol. 1986 Apr;80(4):812-7. doi: 10.1104/pp.80.4.812.
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.
我们研究了从豇豆下胚轴分离出的膜泡中赤霉素 A1（GA1）的渗透特性。随着 pH 值降低，GA1 的摄取速率逐渐增加，这表明中性分子比阴离子 GA1 具有更高的渗透性。本研究中使用的膜泡具有液泡型 H（+）转运 ATP 酶，这可以通过吖啶橙荧光的 MgATP 依赖性猝灭和甲胺摄取来测定。然而，MgATP 并没有刺激 GA1 的摄取。在超过 1 微摩尔的浓度下，GA1、GA5 和 GA 使 MgATP 产生的和人为施加的 pH 梯度崩溃，显然是通过作为中性 GA 的 H+穿过膜来实现的。中性 GA 的相对高渗透性和 GA 在去偶联细胞内膜 pH 梯度方面的潜在有害作用支持这样的观点，即 GA1 的积累和区室化必须通过 GA1 向更极性的代谢物转化来发生。
