Actinobacillus pleuropneumoniae two-component system QseB/QseC regulates the transcription of PilM, an important determinant of bacterial adherence and virulence

QseB/QseC is one of the five predicted two-component systems (TCSs) in Actinobacillus pleuropneumoniae. To understand the roles of this TCS in A. pleuropneumoniae, a markerless gene-deletion mutant Delta qseBC was constructed. Differentially expressed (DE) genes in Delta qseBC were filtered by microarray analysis. A total of 44 DE genes were found to be regulated by QseB/QseC system. The transcriptional profile of A. pleuropneumoniae Delta qseBC was compared with that of Delta luxS and catecholamine (CA) stimulations, 13 genes regulated by QseB/QseC were found also regulated by LuxS, and 3 Qse-regulons were co-regulated by CA stimulations, respectively. Binding of QseB to the promoters of three regulons (pilM, glpK and hugZ), which were co-regulated by QseB/QseC and LuxS, was evaluated by electrophoretic mobility-shift assay. Results indicated that pilM was directly regulated by phosphorylated-QseB. Then the pilM deletion mutant Delta pilM was constructed and characterized. Data presented here revealed that adherence ability of Delta pilM to St. Jude porcine lung cells was significantly decreased, and Delta pilM exhibited reduced virulence in pigs, suggesting PilM contributes to the process of A. pleuropneumoniae infection. (C) 2015 Elsevier B.V. All rights reserved.