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紫云英根瘤菌糖基转移酶基因exoL的定位突变及序列分析

宫锋, 李强, 周蓓芸, 宋鸿遇

中科院上海植物生理研究所.上海 200032

摘要

利用转座子Tn5对质粒pJB-B6定位诱变,经同源交换,筛选获得一株Rhizobium huakuii107胞外多糖合成缺陷(Exo~(-))变种RH983。三亲本杂交实验显示,pJB-B6及其亚克隆pJB-B601均可纠正变种RH983的胞外多糖合成缺陷。pJB-B601的2.3kb DNA片段的核苷酸顺序表明,该片段内存在一个完整的开放阅读框架(ORF)。ORF全长1170bp,编码390个氨基酸的蛋白,该蛋白与Rhizobium meliloti的糖基转移酶ExoL有56.7%的同源性,称为RhexoL。利用启动子探测质粒,构建了RhexoL-lacZ转录融合子,发现RhexoL基因5^上游有较强的启动子活性。

关键词： 紫云英根瘤菌; 糖基转移酶基因; 酸性胞外多糖; DNA序列

Region-directed mutagenesis and sequence analysis of exoL gene encoding a glucosyl-transferase of Rhizobium huakuii

Gong Feng, Li Qiang, Zhou Beiyun, Song Yongyu

Institute of Plant Physiology,Chinese Academy of Sciences.Shanghai 200032

Abstract

The resulting plasmid pJB-B601 could restore the Exo~(-) phenotype of Rh983. Determination of the complete nucleotide sequence of the fragment showed that it contained the structural gene of a glucosyl-transferase, as well as the 5^- and 3^- flanking regions. An open reading frame of 1 170 base pairs was identified as R. huakuii exo L gene. The MW of ExoL, as deduced from the nucleotide sequence, was estimated at 44kD. Comparison of the nucleotide sequences revealed a high similarity between the exoL genes of R. huakuii and of R. meliloti. The deduced amino acid sequence of R. huakuii ExoL also showed a high similarity with that of R. meliloti ExoL. Furthermore, the exoL-lacZ transcription fusion was constructed and the expression of exoL-lacZ was analyzed.

Key words: Rhizobium huakuii;Glucosyl -transferasegene;EPS;DNA sequence

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引用本文：

宫锋, 李强, 周蓓芸, 宋鸿遇. 紫云英根瘤菌糖基转移酶基因exoL的定位突变及序列分析[J]. 生理学报 1998; 50 (4): .

Gong Feng, Li Qiang, Zhou Beiyun, Song Yongyu. Region-directed mutagenesis and sequence analysis of exoL gene encoding a glucosyl-transferase of Rhizobium huakuii. Acta Physiol Sin 1998; 50 (4): (in Chinese with English abstract).