CONSERVATION BETWEEN RHIZOBIUM NIF, NTR AND DCT GENES

最近的研究与两组分模型相一致 感觉转导和转录调节，适用于 在许多真细菌物种中有许多生物学反应。 功能域似乎已经进化成重复使用 现有的蛋白质-蛋白质和蛋白质-DNA相互作用 创新监管体制。正在验证是否存在这些 功能域可以通过以下两种方式实现 白粉病杂交基因现有结构域重排后的表型 通过将多个点突变的第二个位点逆转映射到 演示互动域。实验的目的是为了 利用C4-二羧酸盐转运(DCT)、固氮(NIF) 和根瘤菌的氮同化(NTR)基因来检测 模型的有效性；结果将同时揭示 生物氮素必需的基因表达机制 定格。以前的工作提供了nif结构基因和 适当的启动子：：报告基因构建，调控 NifA、ntrB和NTRC基因，以及编码的交替西格玛因子 被全国步枪协会。未发表的工作提供了DCTA结构基因和 调控基因dctB和dctD。杂交基因、表达载体 为了产生调节蛋白，DCTA：：LacZ融合基因 报告转录和各种突变菌株将 建造的。这些工具将促进表型筛选 要了解相似的多肽区域是如何在特定的 在紫花苜蓿根瘤菌中调节多种途径的方式。 预计这项研究将引起广泛的学术和实践兴趣。 因为相关基因产物通过控制植物肿瘤的形成 农杆菌、芽孢杆菌产孢量和清除磷酸盐 和肠道中的趋化性；类似的基因也与 由几种革兰氏阴性菌引起和维持感染 病原菌通过控制柱蛋白基因的表达，调节 铜绿假单胞菌的分化及表达调控 木糖脱脂基因与羧基肽酶G2 假单胞菌。

Recent studies are consistent with a two-component model of sensory transduction and transcriptional regulation that applies to a number of biological responses in many eubacterial species. Functional domains appear to have evolved to make repeated use of existing protein-protein and protein-DNA interactions to create novel regulatory systems. Validating the presence of these functional domains can be achieved by either following regulatory phenotypes after rearranging existing domains in hybrid genes of by mapping second site reversions of numerous point mutations to demonstrate interactive domains. Experiments are designed to utilize C4-dicarboxylate transport (dct), nitrogen fixation (nif) and nitrogen assimilation (ntr) genes of Rhizobium to test the validity of the model; results will simultaneously reveal mechanisms of gene expression essential to biological nitrogen fixation. Previous work provides nif structural genes and appropriate promoter::reporter gene constructions, regulatory genes nifA, ntrB and ntrC, and the alternate sigma factor encoded by ntrA. Unpublished work provides the dctA structural gene and regulatory genes dctB and dctD. Hybrid genes, expression vectors for producing regulatory proteins, a dctA::lacZ fusion gene for reporting transcription and various mutant strains will be constructed. These tools will then facilitate phenotype screening to discover how similar polypeptide regions are used in a specific fashion to regulate numerous pathways in Rhizobium meliloti. Broad academic and practical interest in this study is anticipated because related gene products control plant tumor formation by Agrobacteria, sporulation by Bacillus and phosphate scavenging and chemotaxis in enterics; similar genes are also implicated in initiation and maintenance of infection by several gram negative pathogens by controlling expression of pillin genes, regulation of differentiation by Caulobacter, and control of expression of xylose degredation genes and carboxypeptidase G2 in Pseudomonas.