REGULATION OF DEVELOPMENT IN CAULOBACTER

在革兰氏阴性水生细菌C.新月形， 是细胞不对称分裂的直接结果， 一个不动的柄状细胞和一个新的能动的群集细胞。差异化 表征群集单元的表面结构被组装在 在分裂柄细胞的初始群集极的细胞被膜 在细胞周期中以离散的时间顺序。 这些 发育事件，包括鞭毛生物合成，噬菌体 受体形成和皮利形成由内部信号触发 起源于细胞分裂周期。细胞的连续阶段 分裂周期是这些发育事件的检查点。 我们研究的长期目标是破译基因程序， 控制柄杆菌属的极性形态发生。为了实现这一目标，我们的工作 主要集中在鞭毛上，其组装大约需要 50个鞭毛（弗拉）基因。这些基因被分为四类 （I-IV）在I类基因位于顶部的调节层级内 并调节下面的II-IV类基因的转录。 这项提案的重点是了解细胞周期如何调节 启动这种转录级联和分子机制 控制级联反应中的转录特异性。我们的具体 目标包括：分离所需的sigma因子和调节蛋白 对于从位于细胞顶部附近的II类启动子的转录， 新月柄杆菌弗拉基因层级。2.识别并隔离I类 负责弗拉基因转录偶联起始的基因 级联到细胞周期中的DNA复制。3.检查的依赖性 FlbD对其他II类弗拉基因的活性，用于体内激活 III类和IIB类基因的抑制。4.确定机制 介导从III类表达到IV类表达的过渡 位于弗拉基因层次结构底部的基因。我们提出实验 基于遗传、分子和生物化学方法来实现这些目标， 目标.

Differentiation in the Gram-negative, aquatic bacterium C. crescentus, occurs as the direct result of asymmetric cell division to produce a nonmotile stalked cell and a new, motile swarmer cell. The differentiated surface structures that characterize the swarmer cell are assembled in the cell envelope at the incipient swarmer pole of the dividing stalked cell in a discrete temporal sequence during the cell cycle. These developmental events, which include flagellum biosynthesis, bacteriophage receptor formation, and pili formation, are triggered by internal signals originating from the cell division cycle. Successive stages of the cell division cycle are required as checkpoints for these developmental events. The long term goal of our studies is to decipher the genetic program that controls polar morphogenesis in Caulobacter. To achieve this, our work has focused primarily on the flagellum, whose assembly requires approximately 50 flagellar (fla) genes. These genes have been assigned to four classes (I-IV) within a regulatory hierarchy in which class I genes are at the top of the hierarchy and regulate transcription of class II-IV genes below. The focus of this proposal is to understand how the cell cycle regulates initiation of this transcriptional cascade and the molecular mechanisms that control transcriptional specificity within the cascade. Our specific aims include: l. Isolate sigma factors and regulatory proteins required for transcription from the class II promoters located near the top of the Caulobacter crescentus fla gene hierarchy. 2. Identify and isolate class I genes responsible for coupling initiation of fla gene transcriptional cascade to DNA replication in the cell cycle. 3. Examine the dependence of FlbD activity on other class II fla genes for the in vivo activation of class III and repression of class IIB genes. 4. Identify the mechanism that mediates the transition from expression of class III to class IV genes at the bottom of the fla gene hierarchy. We propose experiments based on genetic, molecular, and biochemical approaches to achieve these goals.