DNA replication initiation is required for mid-cell positioning of FtsZ rings in Caulobacter crescentus.
Polymerization of the GTPase FtsZ to form a structure called the Z-ring is the earliest known step in bacterial cell division. Mid-cell Z-ring assembly coincides with the beginning of the replication cycle in the differentiating bacterium Caulobacter crescentus. Z-ring disassembly occurs at the end of the division cycle, resulting in the complete degradation of FtsZ from both stalked and swarmer progeny cells. New Z-rings can only form in the replicative stalked cell. Conditional mutants in DNA replication were used to determine what role DNA replication events play in the process of Z-ring assembly at different stages in the cell cycle. Z-ring assembly occurred even when early stages of DNA replication were blocked; however, the Z-rings were localized at a subpolar region of the cell. Z-rings only assembled at the proper mid-cell location if DNA replication had initiated. Z-ring assembly coincided with areas containing little or no DNA, and Z-rings could not form over an unreplicated chromosome. Overexpressed FtsZ in the absence of DNA replication did not stimulate productive mid-cell Z-ring assembly but, instead, caused the ends of cells to constrict over an extended area away from the nucleoid. These results indicate that the state of chromosome replication is a major determinant of Z-ring localization in Caulobacter.
Indiana University, Department of Biology, Bloomington, IN 47405, USA.
Ellen M
EM
Quardokus
Yves V
YV
Brun
D001426:Bacterial Proteins / Q000502:physiology*; D016935:Caulobacter crescentus / Q000166:cytology / Q000235:genetics* / Q000502:physiology; D002453:Cell Cycle; D002455:Cell Division / Q000235:genetics / Q000502:physiology; D003598:Cytoskeletal Proteins; D004261:DNA Replication; D004269:DNA, Bacterial / Q000096:biosynthesis / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial
D001426:Bacterial Proteins; D003598:Cytoskeletal Proteins; D004269:DNA, Bacterial; C071525:FtsZ protein, Bacteria