Hayashi K, Ogino K, Oono Y, Uchimiya H, Nozaki H
Department of Biochemistry, Okayama University of Science, Japan.
J Antibiot (Tokyo). 2001 Jul;54(7):573-81. doi: 10.7164/antibiotics.54.573.
Bio-probes that inhibit the action of auxin are useful tools for the study of auxin signaling. To screen for specific inhibitors of auxin signaling, we used an Arabidopsis transgenic line harboring the auxin-inducible promoter derived from PS-IAA4/5 and the reporter gene, GUS (beta-glucuronidase). In this transgenic plant, the exogenous auxin specifically enhanced the expression of the GUS reporter gene. A novel 22-membered spiroketal-macrolide, yokonolide A (1), and related previously known compound, A82548A (2), were isolated from Streptomyces diastatochromogenes B59 as inhibitors of auxin inducible gene expression. The absolute structure of I was determined by detailed spectral analyses and chemical derivatization. 1 and 2 completely inhibited the auxin-induced transcription of the reporter gene at 5 and 1 microm, respectively. In contrast, 1 and 2 did not affect the translation of GUS reporter transcripts. In addition, 1 and 2 did not inhibit the gibberellin-induced alpha-amylase expression at 100 microM in barley aleurone cells. These results suggest that 1 and 2 specifically inhibit auxin signaling leading to auxin-mediated gene expression.
抑制生长素作用的生物探针是研究生长素信号传导的有用工具。为了筛选生长素信号传导的特异性抑制剂，我们使用了一种拟南芥转基因株系，该株系含有源自PS-IAA4/5的生长素诱导型启动子和报告基因GUS（β-葡萄糖醛酸酶）。在这种转基因植物中，外源生长素特异性增强了GUS报告基因的表达。从产色链霉菌B59中分离出一种新型的22元螺环内酯大环内酯类化合物—— yokonolide A（1）以及相关的已知化合物A82548A（2），它们可作为生长素诱导基因表达的抑制剂。通过详细的光谱分析和化学衍生化确定了1的绝对结构。1和2分别在5和1微摩尔浓度时完全抑制了报告基因的生长素诱导转录。相比之下，1和2不影响GUS报告基因转录本的翻译。此外，在大麦糊粉层细胞中，1和2在100微摩尔浓度时不抑制赤霉素诱导的α-淀粉酶表达。这些结果表明，1和2特异性抑制导致生长素介导基因表达的生长素信号传导。
