James W. Gober

Expression of positional information during cell differentiation in caulobacter

The asymmetric targeting of proteins to the Caulobacter predivisional cell poles yields dissimilar progeny. We show that the products of transcriptional reporter gene fusions to a flagellin gene and to the flagellar hook operon are segregated to the progeny swarmer cell. This segregation does not depend on sequences within the mRNA, but on the upstream regulatory region. The subset of developmentally regulated flagellar genes that exhibit mRNA segregation has the same upstream cis-acting elements: an activator-binding site known as the ftr sequence and an IHF-binding site. We propose that these genes are preferentially transcribed from the chromosome in the incipient swarmer cell pole of the predivisional cell.

Positional information during Caulobacter cell differentiation

The formation of two distinct daughter cells upon division of the bacterium Caulobacter crescentus is the result of asymmetry in the predivisional cell, in part due to localization of both flagellar and chemotaxis proteins to the swarmer cell pole. Recent evidence suggests that both localized transcription and protein targeting directed by specific amino acid sequence are involved in the localization.

Positioning of gene products during Caulobacter cell differentiation

Summary Caulobacter crescentus has one of the simplest known developmental programs that exhibits both temporal and spatial organization. A hallmark of the Caulobacter cell cycle is that the progeny cells that result from each cell division differ from one another with respect to structure and developmental program. The process of establishing asymmetry prior to cell division requires that a number of gene products be targeted to a pole of the predivisional cell and consequently segregated to one of the two progeny. Several products involved in flagellar biogenesis and the chemotaxis machinery are segregated to the swarmer cell. Evidence suggests that the protein product of some fla and che genes is targeted to the incipient swarmer cell pole. In the case of other flagellar genes, it is the mRNA that is apparently segregated to the swarmer cell. Two heat shock proteins, DnaK and Lon are specifically segregated to the progeny stalked cell.