Separation of temporal control and trans-acting modulation of flagellin and chemotaxis genes in Caulobacter.

The genes involved in the biogenesis of the flagellum and the chemotaxis machinery are temporally regulated during the Caulobacter crescentus cell cycle. Using plasmid complementation, we have mapped the extent of the flaY and flaE genes. These genes function in trans to regulate the expression of the flagellin genes and the chemotaxis genes. We have found that the trans regulation that modulates the amount of the flagellins and the chemotaxis proteins can be separated from the temporal control of fla and che gene expression. This conclusion is based on two observations: the low level of synthesis of flagellins and chemotaxis proteins in flaY and flaE mutant strains occurred at the correct time in the cell cycle, and complementation with plasmids containing intact flaY and flaE genes resulted in the synthesis of normal levels of flagellins and chemotaxis gene products with the maintenance of temporal cell cycle control.