Functions for Glutamine-Metabolizing Enzymes, Expressed in Vascular Tissues, in the Remobilization and Utilization of Nitrogen in Rice Plants

用免疫细胞学方法研究了水稻叶片维管束中谷氨酰胺合成酶（GS 1）和依赖于NADH的谷氨酸合成酶（NADH-GOGAT）的细胞定位。GS1蛋白在衰老叶片中定位于伴胞和维管薄壁细胞中，表明GS1在叶片氮素输出的谷氨酰胺合成中起重要作用; NADH-GOGAT蛋白在未展开的非绿色叶片中定位于韧皮部和木质部溶质转运的细胞中。这一结果表明，GOGAT对通过维管系统转运的谷氨酰胺转化为谷氨酸以进一步用于生物合成过程起着重要作用。在根中，NADH-GOGAT mRNA和蛋白质的表达受到氮素供应的极大刺激。为了研究诱导性增加的分子机制，获得了含有预期启动子区域的约14-kb长的基因组克隆并测序。农杆菌介导的水稻植株转化是为我的品种，Sasanishiki，研究表达的调控。

Cellular localization of cytosolic glutamine synthetase (GS1) protein, as well as NADH-dependent glutamate synthase (NADH-GOGAT), in vascular bundles of rice leaves have been investigated immunocytologically. The GS1 protein in senescing leaf blade was located in companion cells and vascular parenchyma cells, suggesting that the GS1 is important for the synthesis of glutamine for export of leaf nitrogen.NADH-GOGAT protein was detected in cells, which are considered to be active in the transport of solutes from phloem and xylem, in unexpanden, non-green leaf blade. This results indicates this GOGAT is important for the conversion of glutamine, transported via vascular system, to glutamate for the further use in the biosynthetic processes.In the roots, the expression of NADH-GOGAT mRNA and that of protein were greatly stimulated by the supply of nitrogen. To investigate the molecular mechanisms for the inducible increase, about 14-kb long genomic clones containing the expected promoter-region were obtained and sequenced. Agrobacterium-mediated transformation of rice plants is developed for my cultivar, Sasanishiki, to investigate the regulation of the expression.