US-Switzerland Cooperative Research: Molecular Analysis of Host Range in Several Rhizobium Species

本文对“几种根瘤菌寄主范围的分子分析”的建议进行了讨论。 bium Species”之间的Steven G.普埃普克大学 密苏里州，哥伦比亚，和博士威廉J.布劳顿的学校 de Biologie Moleculaire des Plantes Approximeures，Chambesy/日内瓦， 瑞士，由NSF根据美国-瑞士合作组织批准 科学计划。 研究人员建议了解大豆、豇豆和其他 豆科植物被广泛的宿主范围的根瘤菌侵染。 微型模型- 生物是费氏根瘤菌257（在哥伦比亚研究）和根瘤菌， bium sp. NGR 234（在日内瓦研究）。 使用Tn 5诱变， 研究人员已经分离出257菌株的两个不寻常的突变体 使未被亲本菌株侵染的大豆品种侵染。 我们打算将这两种突变体的分析与 根瘤菌NGR 234利用可利用的特性 以帮助阐明宿主特异性的基础。 菌株257的一个突变体在染色体上具有Tn 5，而另一个突变体在染色体上具有Tn 5。 在sym质粒中有转座子。 调查人员已 含有Tn 5位点侧翼DNA的分离的cosplay 插入，亚克隆感兴趣的片段，并将它们定位。 这个提议希望能定义负作用的寄主范围基因 并在NGR 234中寻找对应物。 博士 布劳顿已经分离出一系列具有正作用的寄主范围基因 并从生理和基因上定义它们。 第二个目的 合作的目的是在257菌株中寻找类似的基因。 这些目标的实现将有助于确定 正作用基因和负作用基因在确定 寄主范围广的根瘤菌。

This proposal on "Molecular Analysis of Host Range in Several Rhizo- bium Species" between Dr. Steven G. Pueppke of the University of Missouri, Columbia, and Dr. William J. Broughton of the Laboratoire de Biologie Moleculaire des Plantes Superieures, Chambesy/Geneva, Switzerland, is approved by NSF under the US-Switzerland Cooperative Science Program. The researchers propose to understand how soybean, cowpea, and other legumes are nodulated by broad host-range rhizobia. The model microor- ganisms are rhizobium fredii 257 (researched at Columbia) and rhizo- bium sp. NGR234 (researched at Geneva). Using Tn5 mutagenesis, the investigators already have isolated two unusual mutants of strain 257 that nodulate soybean cultivars not nodulated by the parental strain. The intend to coordinate analysis of these two mutants with that of Rhizobium sp. NGR234 to exploit distinctions which can be exploited to help elucidate the basis of host specificity. One mutant of strain 257 has Tn5 in the chromosome while the other has the transposon in the sym plasmid. The investigators have isolated cosmids containing DNA flanking the sites of the Tn5 insertion, subcloned the fragments of interest, and are mapping them. This proposal hopes to define the negatively-acting host range genes contained in these clones and search for counterparts in NGR234. Dr. Broughton has isolated a series of positively-acting host range genes and is defining them physically and genetically. A second objective of the collaboration is to seek analogous genes in strain 257. Achievement of these objectives will help determine the relative contributions of positively and negatively acting genes in specifying host range in broad host-range rhizobia.