TY - DATA T1 - An Allele of an Ancestral Transcription Factor Dependent on a Horizontally Acquired Gene Product PY - 2012/12/27 AU - H. Deborah Chen AU - Mollie W. Jewett AU - Eduardo A. Groisman UR - https://plos.figshare.com/articles/dataset/An_Allele_of_an_Ancestral_Transcription_Factor_Dependent_on_a_Horizontally_Acquired_Gene_Product__/115294 DO - 10.1371/journal.pgen.1003060 L4 - https://ndownloader.figshare.com/files/280407 L4 - https://ndownloader.figshare.com/files/280470 L4 - https://ndownloader.figshare.com/files/280500 L4 - https://ndownloader.figshare.com/files/280558 L4 - https://ndownloader.figshare.com/files/280601 L4 - https://ndownloader.figshare.com/files/280655 L4 - https://ndownloader.figshare.com/files/280766 L4 - https://ndownloader.figshare.com/files/280846 KW - allele KW - ancestral KW - transcription KW - horizontally KW - acquired KW - product N2 - Changes in gene regulatory circuits often give rise to phenotypic differences among closely related organisms. In bacteria, these changes can result from alterations in the ancestral genome and/or be brought about by genes acquired by horizontal transfer. Here, we identify an allele of the ancestral transcription factor PmrA that requires the horizontally acquired pmrD gene product to promote gene expression. We determined that a single amino acid difference between the PmrA proteins from the human adapted Salmonella enterica serovar Paratyphi B and the broad host range S. enterica serovar Typhimurium rendered transcription of PmrA-activated genes dependent on the PmrD protein in the former but not the latter serovar. Bacteria harboring the serovar Typhimurium allele exhibited polymyxin B resistance under PmrA- or under PmrA- and PmrD-inducing conditions. By contrast, isogenic strains with the serovar Paratyphi B allele displayed PmrA-regulated polymyxin B resistance only when experiencing activating conditions for both PmrA and PmrD. We establish that the two PmrA orthologs display quantitative differences in several biochemical properties. Strains harboring the serovar Paratyphi B allele showed enhanced biofilm formation, a property that might promote serovar Paratyphi B's chronic infection of the gallbladder. Our findings illustrate how subtle differences in ancestral genes can impact the ability of horizontally acquired genes to confer new properties. ER -