Effects of gibberellins on proteins that cross-link microtubules to the plasma membrane

1.从烟草培养细胞中分离微管-质膜交联蛋白质--在从烟草BY-2细胞的原生质体制备的微原生质体制备的提取物中的微管蛋白在不存在任何微管稳定剂的情况下聚合成微管。聚合后的微管形成束，束内相邻微管之间存在横桥。通过组装和拆卸的方法将65Kd的蛋白质与微管蛋白共纯化。发现该蛋白质具有交联微管的能力。利用针对65Kd蛋白的抗体进行免疫荧光显微镜观察，发现该蛋白在烟草BY-2细胞中与微管共分布.烟草培养细胞中微管和质膜之间的交叉桥结构-由烟草BY-2细胞制备的膜影具有结合在由烟草BY-2微型原生质体制备的提取物中聚合的微管的能力。用0.6 M KCl或胰蛋白酶处理消除了鬼结合微管的能力，这表明结合所必需的因子是蛋白质，并被高浓度KCl提取。在存在的紫杉醇，微管稳定剂，微管聚合在提取物中绑定到鬼。KCl消除的因子似乎具有微管稳定活性。在紫杉醇存在的情况下，微管在提取物中聚合并附着在血影上，而从纯化的微管蛋白中聚合的微管则没有，这表明提取物中存在微管附着在膜上所必需的因子.赤霉素A_3（GA_3）对玉米幼苗中胚轴细胞微管的稳定作用用GA_3处理的中胚轴制备的原生质体中的微管比未经GA_3处理的中胚轴制备的原生质体中的微管稳定。

1. Isolation of a microtubule-plasma membrane cross-linking protein from tobacco cultured cells - Tubulin in the extract prepared from miniprotoplasts that had been prepared from protoplasts of tobacco BY-2 cells polymerized into microtubules in the absence of any microtubule-stabilizing agents. The polymerized microtubules formed bundles and between adjacent microtubules in the bundle cross-bridges were observed. A protein of 65Kd was copurified with tubulin by assembly and disassembly method. The protein was found to have the ability to cross-link microtubules. Immunofluorescence microscopy using antibodies against the 65Kd protein revealed that this protein is codistributed with microtubules in tobacco BY-2 cells.2. Cross-bridge structures between microtubules and plasma membrane in tobacco cultured cells - Membrane ghosts prepared from tobacco BY-2 cells have the ability to bind microtubules that were polymerized in the extract prepared from tobacco BY-2 miniprotoplasts. Treatment with 0.6 M KCl or trypsin eliminated the ability of the ghosts to bind microtubules, indicating a factor that is necessary for the binding is protein and is extracted by high concentrations of KCl. In the presence of taxol, a microtubule-stabilizing agent, microtubules polymerized in the extract were bound to the ghosts. The factor eliminated by KCl seems to have a microtubule-stabilizing activity. Microtubules polymerized in the extract attached to the ghost in the presence of taxol, but microtubules polymerized from purified tubulin didn't, indicating the presence in the extract of factor(s) that is necessary for the attachment of microtubules to the membrane.3. Microtubule-stabilizing effect of gibberellin A_3 (GA_3) in maize mesocotyl cells - GA_3 stabilized microtubules in mesocotyl cells of maize seedlings. Microtubules in protoplasts prepared from mesocotyls of GA_3-treated seedlings were more stable than those in protoplasts prepared from GA_3-untreated seedlings.