Agrobacterium tumefaciens C58 contains four replicons, circular chromosome (CC), linear chromosome (LC), cryptic plasmid (pAt), and tumor-inducing plasmid (pTi), and grows by polar growth from a single growth pole (GP), while the old cell compartment and its old pole (OP) do not elongate. We monitored the replication and segregation of these four genetic elements during polar growth. The three largest replicons (CC, LC, pAt) reside in the OP compartment prior to replication; post replication one copy migrates to the GP prior to division. CC resides at a fixed location at the OP and replicates first. LC does not stay fixed at the OP once the cell cycle begins and replicates from varied locations 20 min later than CC. pAt localizes similarly to LC prior to replication, but replicates before the LC and after the CC. pTi does not have a fixed location, and post replication it segregates randomly throughout old and new cell compartments, while undergoing one to three rounds of replication during a single cell cycle. Segregation of the CC and LC is dependent on the GP and OP identity factors PopZ and PodJ, respectively. Without PopZ, replicated CC and LC do not efficiently partition, resulting in sibling cells without CC or LC. Without PodJ, the CC and LC exhibit abnormal localization to the GP at the beginning of the cell cycle and replicate from this position. These data reveal PodJ plays an essential role in CC and LC tethering to the OP during early stages of polar growth.

根癌农杆菌C58包含四个复制子，环状染色体（CC），线性染色体（LC），隐性质粒（pAt）和肿瘤诱导质粒（pTi），并通过极性生长从单个生长极（GP）生长，而旧细胞舱室及其旧杆（OP）不会拉长。我们在极地生长过程中监测了这四个遗传因素的复制和分离。复制前，三个最大的复制子（CC，LC，pAt）位于OP隔室中。复制后，一个副本将在分区之前迁移到GP。CC位于OP的固定位置，然后首先复制。一旦细胞周期开始并在CC以后20分钟从不同的位置复制，LC就不会在OP处保持固定。pAt在复制之前与LC相似，但在LC之前和CC之后复制。pTi没有固定位置，复制后，它会随机分布在新旧细胞室中，同时在一个细胞周期内进行一到三轮复制。CC和LC的隔离分别取决于GP和OP身份因子PopZ和PodJ。没有PopZ，复制的CC和LC将无法有效分区，从而导致没有CC或LC的兄弟单元。没有PodJ，CC和LC在细胞周期开始时对GP的定位异常，并从该位置复制。这些数据表明，PodJ在极性生长的早期阶段在CC和LC系结至OP的过程中起着至关重要的作用。CC和LC的隔离分别取决于GP和OP身份因子PopZ和PodJ。没有PopZ，复制的CC和LC将无法有效分区，从而导致没有CC或LC的兄弟单元。没有PodJ，CC和LC在细胞周期开始时对GP的定位异常，并从该位置复制。这些数据表明，PodJ在极性生长的早期阶段在CC和LC系结至OP的过程中起着至关重要的作用。CC和LC的隔离分别取决于GP和OP身份因子PopZ和PodJ。没有PopZ，复制的CC和LC将无法有效分区，从而导致没有CC或LC的兄弟单元。没有PodJ，CC和LC在细胞周期开始时对GP的定位异常，并从该位置复制。这些数据表明，PodJ在极性生长的早期阶段在CC和LC系结至OP的过程中起着至关重要的作用。