Genetics of Rhizobium-Legume Symbiotic N2 Fixation

该研究计划的目标是进行分子 根瘤菌-豆科植物共生的遗传分析， 世界粮食生产，具有重要的农学意义。 的 在分子水平上研究共生体， 了解两种不同的生物如何相互作用， 基本的生物化学生命过程和相互调节 负责这些过程的基因。 为了实现这一点，作为 基因探针，翻译，框内基因融合将是 构建了根瘤菌固氮基因与E. coli lacZ（编码B-半乳糖苷酶）、uidA（编码B- 葡萄糖醛酸酶）或费氏弧菌（编码细菌 荧光素酶）基因的完美基因置换。 了解如何 固氮在共生和自由生长过程中都是精心安排的。 活细菌生长，使用这些基因工程根瘤菌 菌株，固氮过程的调节将是 在培养物和植物中进行比较。 为了了解这些 过程是由基因控制的，基因负责 这种调节，将分离定义根瘤菌突变体， 这些基因已经被改变，将被构建， 将测试由这种改变产生的表型。 因为它提供了一个强大的方法来操纵基因， 以明确的方式，向任何细菌传递的能力 通过噬菌体的DNA序列将被利用。 根瘤菌是一种革兰氏阴性菌属， 豆科植物的根，并刺激根的发育 结节 在这种共生关系中，细菌和植物 能够将大气中的氮（二氮）转化为 生物学上有用的形式，通过称为氮的过程 固定 这个项目的目标是了解基因 导致这种共生关系的调节事件。 重点 将被放置在分离根瘤菌基因， 在固氮和识别机制， 调节这些基因的表达。 这是一个经济上 重要研究领域如共生固氮 是氮肥的有效替代品。

The objectives of this research program are to conduct molecular genetic analyses of the Rhizobium-Legume symbiosis, which, in world food production, is of great agronomic importance. The study of symbioses at the molecular level challenges us to understand how two different organisms intertwine their fundamental biochemical life processes and interregulate the genes responsible for these processes. To accomplish this, as genetic probes, translational, in-frame gene fusions will be constructed between Rhizobium N 2 fixation genes and either E. coli lacZ (encoding B-galactosidase), uidA (encoding B- glucuronidase), or V. fischerii lux (encoding bacterial luciferase) genes by perfect gene replacement. To understand how N 2 fixation is orchestrated during both symbiosis and free- living bacterial growth, using these gene-engineered Rhizobium strains, the regulation of N 2 fixation processes will be compared in culture and in planta. To understand how these processes are genetically controlled, the genes responsible for this regulation, will be isolated defined Rhizobium mutants in which these genes have been altered, will be constructed and the phenotypes resulting from such alterations will be tested. Because it offers a powerful method to manipulate genes in defined ways, the capacity to deliver to any bacterium defined DNA sequences via phage will be exploited. Rhizobium is a genus of gram-negative bacteria which can invade the roots of legumes and stimulate the development of root nodules. ln this symbiotic relationship, the bacteria and plant are able to convert atmospheric nitrogen (dinitrogen) to biologically useful forms by the process known as nitrogen fixation. The goal of this project is to understand the genetic regulatory events that bring about this symbiosis. Emphasis will be placed on isolating the Rhizobium genes that participate in nitrogen fixation and on identifying the mechanisms that regulate the expression of these genes. This is an economically important area of research as symbiotic nitrogen fixation represents an efficient alternative to nitrogen fertilizers.