Study on biosynthesis and signal transduction of brassinosteroids

1.豌豆油菜素内酯生物合成及感知/信号转导基因的克隆--成功克隆了油菜素内酯生物合成基因LKB和信号转导基因LKA，并对其结构进行了鉴定。此外，还对lkb和lka突变体进行了鉴定，从而揭示了这些突变体分别是生物合成和感知/信号转导突变体.油菜素类固醇生物合成速率的调节-定量豌豆、拟南芥和番茄芽中内源油菜素类固醇的水平。基于这些数据，证明了在这些植物中存在三个常见的限速步骤，包括菜油烷醇转化为6-脱氧卡西甾酮（C-22羟基化）、6-脱氧卡西甾酮转化为6-脱氧茶甾酮（C-23羟基化）和6-脱氧卡斯甾酮转化为卡斯甾酮（C-6氧化）。利用对油菜素内酯不敏感的番茄突变体cu-3，C-6氧化受感知/信号基因的反馈调节.基因表达-用矮豌豆突变体lkb分离被油菜素上调的基因，称为BLU 1和BLU 2。BLU 1编码一种新的蛋白质，具有26个氨基酸重复序列，并具有高度的同源性豌豆基因S2，已知是在茎中表达，以及鹰嘴豆基因CanST-2，可能参与细胞伸长。BLU 2编码一种新的细胞色素P450，与参与合成防御化合物香豆素的CYP 766 B15基因具有高度同源性。

1. Cloning of brassinosteroid biosynthesis and perception/signal transduction genes of Pisum sativum-The brassinosteroid biosynthesis gene LKB and signal transduction gene LKA were successfully cloned and their structures were elucidated. Furthermore, mutations in the lkb and lka mutants were specified, thereby revealing that these mutants are biosynthesis and perception/signal transduction mutants, respectively.2. Regulation of brassinosteroid biosynthesis rates-The levels of endogenous brassinosteroids in shoots of pea, Arabidopsis and tomato were quantified. Based on these data, the presence of three common rate-limiting steps in these plants was demonstrated, including conversion of campestanol to 6-deoxocathasterone (C-22 hydroxylation), of 6-deoxocathasterone to 6-deoxoteasterone (C-23 hydroxylation) and of 6-deoxocastasterone to castasterone (C-6 oxidation). Using the tomato mutant cu-3 that is insensitive to brassinosteroids, the C-6 oxidation is feedback regulated by perception/signaling gene (s).3. Gene expression-Genes upregulated by brassinolide that were termed BLU1 and BLU2 were isolated using the dwarf pea mutant lkb. BLU1 coded a new protein with 26 amino acid repeats and had a high homology to the pea gene S2 that was known to be expressed in stems, as well as to the chickpea gene CanST-2 that may be involved in cell elongation. BLU2 encoded a new cytochrome P450 with a high homology to the CYP766B15 gene that is involved in the synthesis of coumarin, a defense compound.