Department of Plant Biology, Carnegie Institution of Washington, 290 Panama Street, 94305, Stanford, CA, USA.
Planta. 1983 Apr;157(3):193-201. doi: 10.1007/BF00405182.
Association of (14)C-labelled indole-3-acetic acid (IAA) with membrane particles from zucchini (Cucurbita pepo L.) hypocotyls - previously described as "site III binding" (M. Jacobs and R. Hertel, 1978, Planta 142, 1-10) - is reinterpreted as a carrier-mediated uptake into closed and sealed vesicles driven by a pH gradient. Accumulation of the radioactive auxin is saturable, sensitive to the protonophore, carbonyl cyanide p-trifluoromethoxyphenyl hydrazone (FCCP), and to nigericin, and requires a pH gradient across the membranes with proton concentration greater outside than inside. The pH gradient decays within 1-2 h at 4°C and can be restored by re-equilibration of the particle preparation at more alkaline pH followed by return to more acidic medium. Osmotic shock and sonication release the IAA from the vesicles. 1-N-naphthylphthalamic acid (NPA) and 2,3,5-triiodobenzoic acid (TIBA), both inhibitors of auxin transport in vivo, increase the amount of net IAA accumulation in the vesicles, presumably by blocking efflux. Analogs of NPA less active or inactive in vivo are respectively less active or inactive in vitro. It is proposed that these membrane particles are outside-out plasma membrane vesicles, and that they perform the essential functions of auxin transport according to the chemiosmotic theory, with a specific, saturable proton symport uptake and an export anion carrier which is inhibited by NPA and TIBA.
（14）C 标记的吲哚-3-乙酸（IAA）与西葫芦（Cucurbita pepo L.）下胚轴膜颗粒的结合 - 先前被描述为“位点 III 结合”（M. Jacobs 和 R. Hertel，1978，Planta 142，1-10） - 被重新解释为一种载体介导的摄取进入由 pH 梯度驱动的封闭和密封囊泡。放射性生长素的积累是饱和的，对质子载体羰基氰化物 p-三氟甲氧基苯腙（FCCP）和 Nigericin 敏感，并且需要跨膜的 pH 梯度，质子浓度在膜外大于膜内。在 4°C 下，pH 梯度在 1-2 小时内衰减，并可以通过将颗粒制剂在更碱性 pH 下重新平衡并返回更酸性介质来恢复。渗透休克和超声处理会从囊泡中释放 IAA。1-N-萘基邻苯二甲酰亚胺（NPA）和 2,3,5-三碘苯甲酸（TIBA），都是体内生长素运输的抑制剂，增加了囊泡中净 IAA 积累的量，推测是通过阻断外排。在体内活性较低或无活性的 NPA 类似物在体外的活性分别较低或无活性。据推测，这些膜颗粒是质膜囊泡的外翻形式，它们根据化学渗透理论执行生长素运输的基本功能，具有特定的、饱和的质子协同摄取和被 NPA 和 TIBA 抑制的出口阴离子载体。
