知识与财富的链接
拟南芥的CPD基因编码一种与植物油菜素内酯(brassinosteroids,BRs)生物合成有关的细胞色素P450类固醇单加氧酶(CYP90 )。为探讨油菜素内酯这类新型植物激素在多年生木本植物中生物合成及作用的分子机理,以拟南芥CPD基因的一个cDNA片段为探针,从一种杂交杨 (Populustremula×tremudelois)的cDNA文库中分离出一个长 1 442bp的cDNA片段,然后再以这个cDNA的 5′区为探针,从这种杂交杨的基因组文库中分离出一个长 1 900bp的基因组DNA(gDNA)片段。测序结果表明,这段cDNA的 5′区与这段gDNA的 3′区重合; 由这段cDNA和gDNA组成的读框编码一个由 476个氨基酸组成的分子量为 63kD的蛋白质。该蛋白与拟南芥CYP90的同源性为 78 32%,比后者仅长 4个氨基酸,在所有已知的功能结构域,其中包括与BR生物合成密切相关的类固醇结合位点,也具有较高的同源性,表明CPD基因在一年生的草本和多年生的木本植物之间具有很高的保守性。系统树分析还表明,CYP90蛋白与番茄和玉米的矮化基因产物、鱼的all trans retinoicacid4 hydroxy lase及微澡青菌(Synechocystissp. )的细胞色素P450在进化上有较密切的联系。
Gene CPD (constitutive photomorphogenesis and dwarf) encodes a cytochrome P450 steroid side-chain hydroxylase (CYP90) involved in biosynthesis of brassinosteroids (BRs) in Arabidopsis thanalia.To dissect the molecular mechanism underlying the biosynthesis and action of the new phytohormone in perennial woody plants,a 1 442 bp cDNA and a 1 900 bp genomic DNA fragments whose 3′- half was well overlapped with the 5′-half of the former were obtained from a hybrid aspen (Populus tremula×tremudelois) by screening of the cDNA and genomic DNA libraries of this tree using a cDNA fragment from the Arabidopsis CPD gene in the present study.Sequence analysis revealed that the open reading frame comprising the cDNA and genomic DNA fragments encoded a protein of 476 amino acids with a molecular weight of 63 kD.This protein is four amino acid residues longer than Arabidopsis CYP90, and 78.32% identical to the latter.Also it shared high homologies with the Arabidopsis CYP90 in all known functional domains,including steroid-binding region closely related to BR biosynthesis,indicating a high conservatism of the putative CDP gene between annual herb and perennial woody plant species.
