Regulatory network of a conserved polar factor in Sinorhizobium meliloti

描述（由申请人提供）：尽管细菌细胞尺寸微小，但在亚细胞和分子水平上表现出广泛程度的动态、程序化组织。大量的专用细胞成分定位并在适当的位置和时间组装，以确保适应不断变化的环境条件，包括入侵其他生物体时遇到的环境条件。该项目旨在阐明一个保守的极性因子的功能网络如何控制α-变形杆菌Sinorhizobium meliloti中的多种细胞凋亡相关活动，该活动感染豆科植物的根以形成共生。具体而言，PodJ 1蛋白（SMc 02230）定位于较新的细胞极，并且podJ 1基因的缺失干扰鞭毛运动性、胞外多糖产生、细胞分裂以及对洗涤剂和渗透胁迫的抗性。微阵列分析表明，podJ 1影响129个基因的表达，其中大多数与podJ 1突变体中观察到的表型相关。在没有PodJ 1的情况下，表达降低最严重的基因是tacA（SMc 04011），其编码保守的转录激活因子。此外，抑制分析导致9个因子的鉴定，与podJ 1基因相互作用。两个抑制子（SMc 00067和SMc 03872）中的突变似乎废除了琥珀聚糖的合成，琥珀聚糖是一种对共生至关重要的胞外多糖。另一个抑制基因编码保守的组氨酸激酶PleC（SMc 02369）。 本研究将（1）研究SMc 00067和SMc 03872在琥珀聚糖生产中的作用，（2）研究必需组氨酸激酶PleC的调节活性，（3）确定TacA转录激活因子的功能。这些因素是如何影响S.苜蓿生理学将使用多种方法进行评估，包括遗传和微阵列分析、表型测定和显微镜检查。调查结果将有助于阐明在α-变形菌群中似乎重复的调控回路，其中包括布鲁氏菌和巴尔通体等病原体。所产生的见解将提供更好的理解感染期间发生的空间和时间协调。

DESCRIPTION (provided by applicant): Despite their minute size, bacterial cells exhibit an extensive degree of dynamic, programmed organization at the subcellular and molecular levels. A plethora of dedicated cellular components localize to and assemble at appropriate positions and times to ensure fitness in ever-changing environmental conditions, including those encountered when intruding into other organisms. The proposed project seeks to clarify how the functional network of a conserved polar factor controls multiple cell envelope-associated activities in the alpha- proteobacterium Sinorhizobium meliloti, which infects the roots of legume plants to form symbiosis. Specifically, the PodJ1 protein (SMc02230) localizes to the newer cell pole and deletion of the podJ1 gene interferes with flagellar motility, exopolysaccharide production, cell division, and resistance against detergents and osmotic stress. Microarray analysis indicated that podJ1 affects the expression of 129 genes, the majority of which correlate with phenotypes observed in the podJ1 mutant. In the absence of PodJ1, the gene whose expression was most severely reduced is tacA (SMc04011), which encodes a conserved transcriptional activator. In addition, suppressor analysis led to the identification of nine factos that interact genetically with podJ1. Null mutations in two of the suppressors (SMc00067 and SMc03872) appear to abolish synthesis of succinoglycan, an exopolysaccharide critical for symbiosis. Another suppressor encodes the conserved histidine kinase PleC (SMc02369). The proposed research will (1) examine the roles of SMc00067 and SMc03872 in succinoglycan production, (2) investigate the regulatory activities of the essential histidine kinase PleC, and () determine the function of the TacA transcriptional activator. How these factors contribute to different aspects of S. meliloti physiology will be assessed using multiple approaches, including genetic and microarray analyses, phenotypic assays, and microscopy. Results from the investigation will help elucidate regulatory circuits that appear to be iterated in the alpha-proteobacteria group, which includes pathogens such as Brucella and Bartonella. The insights generated will provide better understanding of the spatial and temporal coordination that occurs during infection.