Analysis of Brassinosteroid Biosynthesis in Arabidopsis thaliana

油菜素内酯是一种公认的调节植物生长的植物激素。缺乏内源性油菜素内酯水平的拟南芥矮突变体已被用于油菜素内酯的生物合成研究。本研究对拟南芥油菜素内酯的生物合成调控进行了研究。1)建立完整植株代谢研究的实验条件。我们已经测试了几种处理底物油菜素内酯对拟南芥完整植株的方法。在液体培养的幼苗中观察到最高的效率。拟南芥茎内直接注射castasterone的代谢活性较弱，微注射效果不明显。2)油菜素内酯合成缺陷矮化突变体的鉴定。在T-DNA插入突变系中发现了一个矮化突变体，其表型与油菜素内酯突变体相似。油菜素内酯的应用和内源性油菜素内酯水平分析表明，这是一种新的油菜素内酯突变体，其对卡斯特酮的代谢活性存在缺陷。人们曾尝试克隆被T-DNA插入干扰的基因，但尚未成功。这项研究将在我们克隆工作取得成功结果后发表。

Brassinosteroid has been recognized as a plant hormone that regulates growth of plants. Dwarf mutants of Arabidopsis thaliana that are deficient in endogenous brassinosteroid levels have been used for studies on the biosynthesis of brassinosteroid. In this study, following subjects have been examined to clarify the regulation of the biosynthesis of brassinosteroid in Arabidopsis.1)Establishment of experimental conditions for metabolic studies with intact plants. We have tested several methods for the treatment of substrate brassinosteroids to the intact plants of Arabidopsis. The highest efficiency was observed in the system using a liquid culture of seedlings. Micro-injection was not effective at all, and slight metabolic activity was observed in the direct injection of castasterone into Arabidopsis stems.2)Characterization of novel dwarf mutant that has defect in brassinosteroidbiosynthesis.A dwarf mutant was found in the T-DNA insertion mutant lines, which had similar phenotype with brassinosteroid mutants. Application of brassinosteroids and analysis of endogenous brassinosteroid levels revealed that it is a novel brassinosteroid mutant that has defect in the metabolic activity of typhasterol to castasterone. Cloning of the gene that is disrupted by the insertion of T-DNA was attempted, although it has not been achieved yet. This study will be published after we get successful results in the cloning work.