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影响紫云英根瘤菌入侵和根瘤发育的exo基因的克隆及分析

黄建斌, 周蓓芸, 宋鸿遇

中科院上海植物生理研究所.上海 200032

摘要

紫云英根瘤菌菌株107的3个胞外多糖缺陷突变株NA-01、02、04不具备诱导宿主植物紫云英结瘤的能力。以NA-01突变位点的DNA片段为探针,从可互补这3个变种的exoR^-11质粒上亚克隆到2.6kb的DNA片段。互补试验表明,2.6kb的片段不仅可纠正突变株的胞外多糖缺陷表型,而且使变种恢复诱导宿主植物形成有效根瘤的能力。2.6kb片段经Tn5定位突变后丧失这种恢复能力,表明该片段带有对应于3个变种的野生型基因。

关键词： exo基因; 克隆; 胞外多糖; 紫云英根瘤菌

Cloning and analysis of exo gene required for nodule invasion and development of Rhizobium astragali

Huang Jianbin, Zhou Beiyun, Song Hongyu

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

Abstract

Three exopolysaccharide (EPS)-deficient mutants NA-01, 02, 04 (Exo~(-)) isolated from wild Rhizobium astragali strains 107 showed no ability to induce nodule formation on the roots of Astragalus sinicus L. From plasmid exo-R^-11 which could complement these three mutants, a 2.6 kb DNA fragment was cloned using 3.1 kb fragment from mutant site of NA-01 as probe. It was shown that the 2.6 kb fragment did not only fully complemented the EPS phenotype of each of the three mutants, but also restored its ability to induce Fix~(+) nodule formation as did the wild-type strain 107. After Tn5 site-directed mutagenesis, the 2.6 kb DNA with Tn5 insertion lost such complementation ability. Therefore, we could conclude that 2.6 kb DNA fragment contained the exo gene which complements the three mutants.

Key words: exo gene;Cloning;Exopolysaccaride;Rhizobium astragali

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引用本文：

黄建斌, 周蓓芸, 宋鸿遇. 影响紫云英根瘤菌入侵和根瘤发育的exo基因的克隆及分析[J]. 生理学报 1997; 49 (3): .

Huang Jianbin, Zhou Beiyun, Song Hongyu. Cloning and analysis of exo gene required for nodule invasion and development of Rhizobium astragali. Acta Physiol Sin 1997; 49 (3): (in Chinese with English abstract).