CYP90C1 and CYP90D1 are involved in different steps in the brassinosteroid biosynthesis pathway in Arabidopsis thaliana
CYP90C1 and CYP90D1 are involved in different steps in the brassinosteroid biosynthesis pathway in Arabidopsis thaliana
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DOI：
10.1111/j.1365-313x.2004.02330.x
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发表时间：
2005-03-01
期刊：
影响因子：
7.2
通讯作者：
Tsukaya, H
中科院分区：
文献类型：
--
作者：
Kim, GT;Fujioka, S;Tsukaya, H
油菜素类固醇(BRs)是一种植物激素，在植物的广泛发育过程中是必不可少的。最近发现了许多导致BRS生物合成早期反应的基因。然而，催化BRs生物合成途径后期步骤的几个酶基因仍有待鉴定，而且只有几个基因负责产生具有生物活性的BRs的反应。我们发现，在BR生物合成途径的后期步骤中，ROT3(ROT3)基因是BR生物合成途径的后期步骤所必需的，该基因编码与拟南芥叶片长度调节有关的酶CYP90C1。类固醇转化为卡斯特酮似乎需要ROT3，这是BR途径中的一个激活步骤。我们还分析了与ROT3关系最密切的基因--CyP90d1，发现ROT3和CyP90d1双突变体具有严重的矮化表型，而cyp90d1单基因敲除突变体没有严重矮化表型。在这些突变体中的BR图谱显示，CYP90D1也参与了BR的生物合成途径。ROT3和CYP90D1在拟南芥叶片中差异表达，这两个基因的突变体在光照条件下对下胚轴伸长的缺陷不同。在黑暗条件下，叶片叶柄细胞色素P90D1的表达受到强烈诱导。本研究结果表明，两种细胞色素P450在BRs生物合成的器官特异性环境调控中发挥着不同的作用。
Brassinosteroids (BRs) are plant hormones that are essential for a wide range of developmental processes in plants. Many of the genes responsible for the early reactions in the biosynthesis of BRs have recently been identified. However, several genes for enzymes that catalyze late steps in the biosynthesis pathways of BRs remain to be identified, and only a few genes responsible for the reactions that produce bioactive BRs have been identified. We found that the ROTUNDIFOLIA3 (ROT3) gene, encoding the enzyme CYP90C1, which was specifically involved in the regulation of leaf length in Arabidopsis thaliana, was required for the late steps in the BR biosynthesis pathway. ROT3 appears to be required for the conversion of typhasterol to castasterone, an activation step in the BR pathway. We also analyzed the gene most closely related to ROT3, CYP90D1, and found that double mutants for ROT3 and CYP90D1 had a severe dwarf phenotype, whereas cyp90d1 single knockout mutants did not. BR profiling in these mutants revealed that CYP90D1 was also involved in BR biosynthesis pathways. ROT3 and CYP90D1 were expressed differentially in leaves of A. thaliana, and the mutants for these two genes differed in their defects in elongation of hypocotyls under light conditions. The expression of CYP90D1 was strongly induced in leaf petioles in the dark. The results of the present study provide evidence that the two cytochrome P450s, CYP90C1 and CYP90D1, play distinct roles in organ-specific environmental regulation of the biosynthesis of BRs.