Regulation of transcript levels of the Arabidopsis cytochrome P450 genes involved in brassinosteroid biosynthesis
Regulation of transcript levels of the Arabidopsis cytochrome P450 genes involved in brassinosteroid biosynthesis
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DOI：
10.1104/pp.005439
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发表时间：
2002-09-01
期刊：
影响因子：
7.4
通讯作者：
Szekeres, M
中科院分区：
文献类型：
--
作者：
Bancos, S;Nomura, T;Szekeres, M
细胞色素P450酶与细胞色素P90和细胞色素P85家族密切相关，催化油菜素类固醇(BR)激素的生物合成中的基本氧化反应。拟南芥的CYP90B1/DWF4和CYP90A1/CPD分别负责类固醇侧链的C-22和C-23羟基化，而CYP85A1催化6-脱氧中间体的C-6氧化，而CYP90C1/ROT3、CYP90D1和CYP85A2的功能尚不清楚，半定量逆转录-聚合酶链式反应分析表明，CYP85和CYP90基因的转录水平受到BR生物合成途径的最终产物油菜素内酯的下调。油菜素内酯对细胞色素P90C1、细胞色素P90D1和细胞色素P85A2基因的反馈控制表明，相应的酶可能也参与了BR的合成。在幼苗发育的第1周，细胞色素P85和细胞色素P90的mRNAs表现出较强的瞬时积累，并具有典型的器官特异性分布。细胞色素P90A1和细胞色素P85A2的转录本主要在地上部表达，根中的细胞色素P90A1、细胞色素P90D1和细胞色素P85A1的mRNAs含量较高，而细胞色素P90B1在植物体内普遍表达。值得注意的是，在BR不敏感的cbb2突变体中，CYP90A1表达的空间模式保持不变，表明器官特异性调控和BR依赖调控是独立的。对拟南芥、豌豆和番茄地上部和根部内源BR的定量气相色谱-质谱分析表明，BR中间体在这些物种中的分配模式相似。在茎和根中，细胞色素P90A1/CPD转录水平与细胞色素P90A1底物6-脱氧雄酮的含量呈负相关，这表明转录调控在控制BR的生物合成中起重要作用。
Cytochrome P450 enzymes of the closely related CYP90 and CYP85 families catalyze essential oxidative reactions in the biosynthesis of brassinosteroid (BR) hormones. Arabidopsis CYP90B1/DWF4 and CYP90A1/CPD are responsible for respective C-22 and C-23 hydroxylation of the steroid side chain and CYP85A1 catalyzes C-6 oxidation of 6-deoxo intermediates, whereas the functions of CYP90C1/ROT3, CYP90D1, and CYP85A2 are still unknown, Semiquantitative reverse transcriptase-polymerase chain reaction analyses show that transcript levels of CYP85 and CYP90 genes are down-regulated by brassinolide, the end product of the BR biosynthesis pathway. Feedback control of the CYP90C1, CYP90D1, and CYP85A2 genes by brassinolide suggests that the corresponding enzymes might also participate in BR synthesis. CYP85 and CYP90 mRNAs show strong and transient accumulation during the 1st week of seedling development, as well as characteristic organ-specific distribution. Transcripts of CYP90A1 and CYP85A2 are preferentially represented in shoots and CYP90C1, CYP90D1, and CYP85A1 mRNAs are more abundant in roots, whereas CYP90B1 is ubiquitously expressed. Remarkably, the spatial pattern of CYP90A1 expression is maintained in the BR-insensitive cbb2 mutant, indicating the independence of organ-specific and BR-dependent regulation. Quantitative gas chromatography-mass spectrometry analysis of endogenous BRs in shoots and roots of Arabidopsis, pea (Pisum sativum), and tomato (Lycopersicon esculentum) reveal similar partitioning patterns of BR intermediates in these species. Inverse correlation between CYP90A1/ CPD transcript levels and the amounts of the CYP90A1 substrate 6-deoxocathasterone in shoots and roots suggests that transcriptional regulation plays an important role in controlling BR biosynthesis.