Regulation of the pAD1 sex pheromone response in Enterococcus faecalis: construction and characterization of lacZ transcriptional fusions in a key control region of the plasmid

Abstract

Strains carrying the Enterococcus (formerly Streptococcus) faecalis plasmid pAD1 responded to exogenous sex pheromone by inducing a number of gene products which facilitated mating. A 7-kilobase region of pAD1 was identified which contained genes that are important for the regulation of this response. Using the transposon Tn917-lac delivery vector pTV32Ts, we generated a number of fusions that allowed us to examine transcription in this region. At least three transcriptional units were identified by grouping fusions by their phenotype, direction of transcription, and response to pheromone. Transcription from one set of fusions was sensitive to the presence of pheromone. Analysis of the patterns of protein production previously shown to be induced in the presence of pheromone provided more information on the function of the genes of interest. We postulate the existence of two negative regulatory proteins that act coordinately to repress the pheromone response, one of which may be involved in sensing or transmitting the pheromone signal, and at least one positive regulatory protein whose synthesis is dependent on the presence of pheromone. In addition, the isolation of a relatively small deletion mutant capable of producing cAD1. the pheromone specific for pAD1-containing cells, indicates that a factor(s) that is important for the shutdown of endogenous pheromone is also present in this region.