The goal of this laboratory is continue to the develop the Agrobacterium-plant pathosystem as a leading model for host-microbe interactions and for pheromone-mediated bacterial communication. In the past 15 years, cell-cell communication via diffusible chemical signals has come to be appreciated as an important property of many bacteria, especially those associated with plant, animal, or human hosts. Among these signals, acyl-homoserine lactones (AHLs) are especially widespread among the proteobacteria. AHLs are generally synthesized by proteins resembling the Luxl protein of Vibrio fischeri, and detected by transcription factors resembling the V. ficsheri LuxR protein. My lab focuses on genetic and biochemical studies of several LuxR-type proteins. One of these systems, Tral and TraR of Agrobacterium tumefaciens regulate genes required for the conjugation and vegetative replication of a large tumor-inducing plasmid. Cepl and CepR of Burkholderia cenocepacia regulate many genes on several chromosomes and plasmid of this bacterium, while Yenl and YenR of Yersinia enterocolitica regulate an unknown number of genes, including yenS, which appears to encode a small regulatory RNA. We will continue to test the hypothesis that TraR and CepR require AHL for correct folding, and must bind this pheromone during their own synthesis on ribosomes. We will also study how the activating region or regions of TraR interact with RNA polymerase. We will identify target genes activated by CepR and YenR. YenR is unusual in that it is active as an apo-protein and its activity is inhibited by AHLs. We will try to reconstitute this inhibition in vitro. Finally, we will test the idea that yenS encodes a small non-coding RNA and determine whether this sRNA regulates the stability of target mRNAs by forming heteroduplexes. Direct targets of YenR and YenS will be identified and assessed for their roles in the biology and ecology of Y. enterocolitica and Y. pestis.