Functional expression and regulation of nitrate assimilation in plants.

在本研究项目下，对以下四个主题进行了研究。硝酸还原酶（NR）和亚硝酸还原酶（NiR）的分子克隆和基因分析。从水稻叶片和根中提取mRNA，构建cDNA文库。获得NiR的DNA克隆并分析其碱基序列（Ida）。分离培养菠菜细胞NR的cDNA克隆并分析其结构（Nakagawa）. NR和NiR基因表达的机制及酶活性的调节。从大麦叶和根中分离纯化NR，并测定其免疫学特性。研究了光照、温度、铵离子等环境因子对NR诱导的影响.胞质膜硝酸盐载体蛋白的分离及其基因分析。对水稻种子进行诱变处理，获得了一些硝酸盐吸收失败的突变体（长谷川）。分离了蓝绿藻细胞质膜中包含的硝酸盐转运相关蛋白质的基因，并分析了其碱基序列（Omata）。建立了一种利用液-液两相分离技术分离蓝藻细胞质膜的简便方法（Ohnori）.植物对硝态氮的吸收与运转。通过改变培养液（Arima）中硝酸盐浓度，改变水稻根系吸收硝酸盐的活性。水稻韧皮部汁液中的氨基酸组成因氮素营养种类的改变而发生变化。

Under this research project, following four main themes have been investigated.1. Molecular cloning and gene analysis of nitrate reductase (NR) and nitrite reductase (NiR). A cDNA library was made using mRNA isolated from leaves and roots of rice plant. A DNA clone for NiR was obtained and its base sequence was analyzed (Ida). A cDNA clone for NR of cultured spinach cells was isolated and its structure was analyzed (Nakagawa).2. The mechanism of gene expression of NR and NiR, and regulation of enzymic activities. NR was isolated from leaves and roots of barley plant, purified and its immunological properties were determined (0ji). Effects of environmental factors such as light, temperature and ammonium ion on NR induction was determined (Yanamoto).3. Isolation of nitrate carrier protein from cytoplasmic membrane, and its gene analysis. Rice seeds were subjected to mutagen treatment and some mutants failed in nitrate uptake were obtained (Hasegawa). A gene for a protein related to nitrate transport and included in cytoplasmic membrane of blue-green algae was isolated and its base sequence was analyzed (Omata). A convenient method for the isolation of cytoplassic membrane from blue-green algal cell using liquid two phase separation technique was established (Ohnori).4. Nitrate uptake by plants and the nitrate translocation. The activity of nitrate uptake in the root of rice plant was changed by changing nitrate concentrations of the incubating medium (Arima). The amino acid composition in the phloem sap of rice plant was changed by changing species of nitrogen-nutrient (Hayashi, Kumazawa).