REGULATION OF EXPRESSION OF THE PILA GENE IN MYXOCOCCUS-XANTHUS

Type IV pill are required for social gliding motility in Myxococcus xa nthus. In this work, the expression of pilin (the pilA gene product) d uring vegetative growth and fruiting-body development was examined. A polyclonal antibody against the pilA gene product (prepilin) was prepa red, along with a pilA-lacZ fusion, and was used to assay expression o f pilA in M. xanthus in different mutant backgrounds. pilA expression required the response regulator pilR but was negatively regulated by t he putative sensor kinase pilS. pilA expression did not require pilB, pilC, or pilT: pilA was also autoregulated; a mutation which altered a n invariant glutamate five residues from the presumed prepilin process ing site eliminated this autoregulation, as did a deletion of the pilA gene. Primer extension and S1 nuclease analysis identified a sigma(54 ) promoter upstream of pilA, consistent with the homology of pilR to t he NtrC family of response regulators. Expression of pilA was found to be developmentally regulated; however, the timing of this expression pattern was not entirely dependent on pilS or pilR. Finally, pilA expr ession was induced by high nutrient concentrations, an effect that was also not dependent on pilS or pilR.