REGULATION OF DEVELOPMENT IN CAULOBACTER

革兰氏阴性水生细菌C.crescentus的分化 作为不对称细胞分裂的直接结果发生，从而产生 不活动的茎细胞和一个新的、活动的蜂群细胞。差异化的 表征沼泽细胞的表面结构组装在 在有柄分裂的细胞的早期丛生极的细胞包膜 在细胞周期中以离散的时间序列。这些 发育事件，包括鞭毛生物合成、噬菌体 受体形成和菌毛形成是由内部信号触发的 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 控制铜绿假单胞菌的极性形态发生。为了实现这一目标，我们的工作包括 主要集中在鞭毛上，其组装需要大约 50个鞭毛(Fla)基因。这些基因被分成四类 (I-IV)在I类基因处于顶端的调控层级内 并调节下面II-IV类基因的转录。 这项建议的重点是了解细胞周期是如何调节的 该转录级联反应的启动及其分子机制 在级联反应中控制转录特异性的基因。我们的特定 目标包括：L。分离所需的西格玛因子和调节蛋白 对于位于基因顶部附近的II类启动子的转录 新月芽孢杆菌Fla基因序列。2.识别和隔离I类 参与FLA基因转录偶联启动的基因 在细胞周期中级联到DNA复制。3.考察对……的依赖 FlbD在其他II类Fla基因上的活性与体内激活 III类和IIB类基因的抑制。4.找出机制 它调节了从III类到IV类的表达 位于FLA基因层次结构最底层的基因。我们建议进行实验 基于遗传、分子和生化方法来实现这些 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.