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Regulation of ascorbate oxidase expression by auxin and cell growth in plants.

植物生长素和细胞生长对抗坏血酸氧化酶表达的调节。

基本信息

批准号：
06660111
负责人：
ESAKA Muneharu
金额：
$ 1.34万
依托单位：
HIROSHIMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

项目摘要

Ascorbate oxidase, which catalizes the one-electron oxidation of ascorbic acid to dehydroascorbic acid, occurs in higher plants such as pumpkin and cucumber. The cDNA clone for ascorbate oxidase was isolated from a cDNA library constructed from poly (A) -rich RNA of tobacco cells by screening with pumpkin ascorbate oxidase cDNA.The amino acid sequence deduced from the nucleotide sequence had 68% and 67% identities to those from pumpkin and cucumber ascorbate oxidase cDNA,respectively. These identities were much lower than the identity (80%) between pumpkin and cucumber. The sequence lacks two cysteine residues forming a disulphide bridge, which is necessary to maintain tertiary structure of ascorbate oxidase protein from pumpkin and cucumber. Ascorbate oxidase is significantly expressed only in cucurbitaceous plants. Indeed, ascorbate oxidase activity was slightly detected in tobacco cells and was much lower than that in pumpkin cells. We suggested that ascorbate oxidase is induced by auxin and that the enzyme plays roles for cell prowth and division. We isolated the pumpkin AOBP cDNA,which encodes a protein that binds to an A/T-rich sequence in the promoter of ascorbate oxidase gene. Part of the AOBP protein, which is composed of 52 amino acid residues, is homologous to the Dof domain of a maize DNA-binding protein, MNB1a. The Dof sequences have five conserved Cys residues and are related to the zinc/DNA-binding domains of steroid hormone receptors and GATA1, suggesting that AOBP is a new zinc finger protein.

抗坏血酸氧化酶，它将抗坏血酸的单电子氧化催化成脱氢抗坏血酸，存在于南瓜和黄瓜等高等植物中。利用南瓜抗坏血酸氧化酶cDNA筛选，从烟草细胞多聚(A)RNA构建的cDNA文库中克隆出抗坏血酸氧化酶基因，其氨基酸序列与南瓜和黄瓜抗坏血酸氧化酶基因的氨基酸序列同源性分别为68%和67%。这些同源性远低于南瓜和黄瓜的同源性(80%)。该序列缺少形成二硫键的两个半胱氨酸残基，这是维持南瓜和黄瓜抗坏血酸氧化酶蛋白三级结构所必需的。抗坏血酸氧化酶只在葫芦科植物中显著表达。事实上，在烟草细胞中也检测到抗坏血酸氧化酶活性，但比南瓜细胞低得多。我们认为抗坏血酸氧化酶是由生长素诱导的，该酶对细胞的活力和分裂起作用。我们克隆了南瓜抗坏血酸氧化酶基因启动子A/T富含A/T序列的编码蛋白AOBP。AOBP蛋白的一部分由52个氨基酸残基组成，与玉米DNA结合蛋白MNB1a的DOF结构域同源。DOF序列有5个保守的Cys残基，与类固醇激素受体和GATA1的锌/DNA结合区相关，提示AOBP是一种新的锌指蛋白。