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Localization of nitrogen-related enzymes in higher plants

高等植物中氮相关酶的定位

基本信息

批准号：
08044187
负责人：
YAMAYA Tomoyuki
金额：
$ 3.71万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

NADH-dependent glutamate synthase (GOGAT) is a key enzyme in nitrogen assimilation and utilization in higher plants. However, little is known on the intracellular localization and molecular properties of this enzyme.In this joint research, intracellular localization of this enzyme protein has been demonstrated by the methods of immuno-gold electron microscopy in rice roots. As the first instance, we determine that the NADH-GOGAT protein locates in plastids of epidermis, exodermis, and central cylinder of the roots. We also succeeded to purify the enzyme from barley roots.Further, genomic clones, as well as cDNA clones, for rice NADH-GOGAT have been isolated and sequenced and the gene structure was thoroughly analyzed. The nucleotide sequences were registered into a Gene-Bank. Expression of this gene has been studied in response to the nitrogen supply in the roots of rice seedlings. The NADH-GOGAT gene is specifically induced within 3 hr after the supply of NH_4^+ among another GOGAT gene and glutamine synthetase genes. When the content of NADH-GOGAT protein in developing leaves were compared among various types of rice, i.e.japonica, indica, and javanica, the leaves in indica-type rice contained less amounts of the protein than those in japonica-type.From those studies, molecular and physiological properties of NADH-GOGAT are getting clear, at least in rice plants.

NADH依赖性谷氨酸合酶（GOGAT）是高等植物氮同化和利用的关键酶。然而，人们对这种酶的细胞内定位和分子特性知之甚少。在这项联合研究中，通过免疫金电子显微镜的方法证明了这种酶蛋白在水稻根部的细胞内定位。首先，我们确定 NADH-GOGAT 蛋白位于表皮、外皮和根部中央圆柱的质体中。我们还成功地从大麦根中纯化了该酶。此外，还分离并测序了水稻NADH-GOGAT的基因组克隆和cDNA克隆，并对基因结构进行了彻底分析。核苷酸序列被登记到基因库中。已经研究了该基因的表达对水稻幼苗根部氮供应的响应。在另一个GOGAT基因和谷氨酰胺合成酶基因中，NADH-GOGAT基因在提供NH_4^+后3小时内被特异性诱导。当比较不同类型的水稻（即粳稻、籼稻和爪哇稻）中正在发育的叶子中 NADH-GOGAT 蛋白质的含量时，发现籼稻类型的叶子中该蛋白质的含量低于粳稻类型的叶子。从这些研究中，NADH-GOGAT 的分子和生理特性正在变得清晰，至少在水稻植物中是这样。