Analysis of Organ-specific expression of glutamine-synthetase gene.

（1）从莴苣种子cDNA文库中克隆了谷氨酰胺合成酶（GS）的全长cDNA。(2)以莴苣谷氨酰胺合成酶cDNA为探针，从水稻文库中分离到3个谷氨酰胺合成酶cDNA（RGS 8、RGS 28和RGS 38）。Northern-blot分析表明，RGS 8主要在根中表达，RGS 28和RGS 38主要在叶中表达。RGS 8和RGS 28为胞质型（GS_1），RGS 38为叶绿体定位型（GS_22）。(3)分离RGS 28基因并测定其完整碱基序列。编码区由10个内含子分隔。RGS 38基因编码区由11个内含子分隔，5'端非编码区由1个内含子分隔。(4)将RGS 28基因的启动子区（约2kb）与GUS基因连接，利用Ti质粒载体将嵌合基因导入烟草植株。在转基因烟草的叶片中检测到高活性的GUS，而在根中检测到非常低的活性，表明在启动子区域中包含决定器官特异性的顺式元件。

(1 ) A full length of CDNA for glutamine synthetase (GS) was isolated from the CDNA library of lettuce seeds.(2) Three cDNAs for glutamine synthetase were isolated from the library of rice by using GS CDNA from lettuce as a probe (RGS8, RGS28 and RGS 38). Northern-blot analysis showed that genes corresponding to these three cDNAs were expressed in each organ: RGS8 mainly in roots, RGS28 and RGS38 mainly in leaves. RGS8 and RGS28 were cytosolic type (GS_1) and RGS38 was chloroplast-located type (GS_22).(3) Gene for RGS28 was isolated and the complete base sequence was determined. The coding region was separated by 10 introns. The coding region of RGS38 gene was separated by 11 introns, and 5' noncoding region by an intron.(4) A promoter region (about 2 kb) of RGS28 gene was connected to GUS gene and the chimera gene was introduced to tobacco plant by using Ti plasmid vector. High activity of GUS was detected in the leaves of the transgenic tobacco plant and very low activity was detected in the root, showing that cis-element to determine the organ-specificity is included in the promoter region.