Localization of the cis-acting regulatory DNA sequences of the Myxococcus xanthus tps and ops genes.

The cis-acting regulatory regions of the tps and ops genes of Myxococcus xanthus were localized by analyzing the expression of fusions of these genes with the lacZ gene. A 201-base-pair (bp) fragment of tps DNa extending 95 bp upstream (-95) from the transcriptional start was sufficient to direct developmentally regulated expression of fusion gene activity. The segment of tps DNA between -95 and -81 contained information necessary for developmental regulation. A segment of ops DNa extending upstream to -131 directed a very low level of ops-lacZ fusion expression, but the inclusion of DNA to -208 greatly increased the amount of developmentally regulated expression. M. xanthus DNA upstream from -108 in the tps gene and -311 in the ops gene was required for maximal expression of gene fusion activity. The upstream regulatory regions of both the tps and ops genes seem to be involved in positive transcriptional regulation. Two mutations, a deletion of 1 bp at -8 in the tps gene and a 3-bp substitution at -27 to -29 in the ops gene, greatly increased the level of vegetative expression of gene fusion activity, suggesting that both genes may also be subject to negative regulation in M. xanthus.