Zbell B A, Walter-Back C, Bucher H
Botanical Institute, Ruprecht-Karls-University, Heidelberg, Federal Republic of Germany.
J Cell Biochem. 1989 Jul;40(3):331-40. doi: 10.1002/jcb.240400309.
Microsomal membranes from carrot suspension cells were phosphorylated in vitro with [gamma-32P]ATP. In the presence of submicromolar concentrations of the natural auxin indoleacetic acid (IAA), a rapid, but transient decrease of the [32P] label could be detected in the phospholipid extracts of the membranes. The phytohormone effect was not the result of an inhibition of the lipid phosphorylation reactions, but was caused by a simultaneous release of water-soluble compounds, which, according to their chromatographic properties, were assumed to contain inositol polyphosphates. Although the [32P]-labeled lipids, as well as the inositol polyphosphates, were not identified unequivocally by chemical analysis, these findings point to an auxin-mediated control of a phosphoinositidase C-like reaction similar to the hormone-stimulated phosphoinositide response in animals. Exogenously applied inositol (1,4,5)trisphosphate [(1,4,5)IP3] was found to release 45Ca2+ from preloaded membrane vesicles of carrot cells. Both the detection of the auxin-stimulated phosphoinositide response and the (1,4,5)IP3-mediated Ca2+ release on isolated cell membranes offer new experimental approaches for the identification of the putative auxin receptor and its signal transduction pathway.
胡萝卜悬浮细胞的微粒体膜在体外与[γ-32P]ATP发生磷酸化反应。在亚微摩尔浓度的天然生长素吲哚乙酸（IAA）存在下，可检测到膜磷脂提取物中[32P]标记迅速但短暂减少。植物激素的这种作用并非脂质磷酸化反应受到抑制的结果，而是由水溶性化合物同时释放所致，根据其色谱特性推测这些化合物含有肌醇多磷酸。尽管通过化学分析未能明确鉴定出[32P]标记的脂质以及肌醇多磷酸，但这些发现表明生长素介导了一种类似于动物中激素刺激的磷脂酰肌醇反应的磷脂酶C样反应的调控。研究发现，外源施加的肌醇（1,4,5）三磷酸[（1,4,5）IP3]可从预先加载的胡萝卜细胞的膜泡中释放45Ca2+。生长素刺激的磷脂酰肌醇反应以及在分离细胞膜上（1,4,5）IP3介导的Ca2+释放的检测，为鉴定假定的生长素受体及其信号转导途径提供了新的实验方法。
