Using the aTc-inducible expression system , we observed that FliZ is unable to increase the activity of Pclass2 promoters in the flhDC mutant -LRB- results not shown -RRB- .
FliZ is responsible for increased levels of FlhC protein independent of flhDC transcription .
HilD therefore represents a potential growth-phase specific mechanism by which FliZ could upregulate flhDC transcription coordinately with SPI-1 genes .
FliZ is needed for eficient induction of the Spi-1 system via post-translational activation of the Spi-1 regulatory protein HilD , which in turn activates flhDC gene transcription .
The flagellar regulator FliZ is a post-transcriptional activator of flhDC that positively regulates SPI1 by activating the hilD-rtsAB cascade .
FliZ increases flhDC synthesis through an unknown mechanism .