CONICET | Buscador de Institutos y Recursos Humanos

Bordetella virulence factors are regulated by several mechanisms, of which the most well-characterized is the Bordetella virulence gene system (BvgAS). When this system is active, the response regulator BvgA activates the expression of the virulence-activated genes. It also activates the expression of bvgR. BvgRrepresses the transcription of the virulence-repressed genes, such as Bordetella bronchiseptica flagellin.Previous studies have used microarray analysis to identify the genes controlled by BvgR. We aimed to characterize more deeply the regulon of genes controlled by BvgR by using RNA sequencing. RNA was prepared from a wild type B. bronchiseptica (Bb WT) and an insertional mutant in bvgR (Bb bvgR-).Comparing the bvgR mutant to the wild type revealed differential expression of 319 genes, of which 221 and 98 were upregulated or downregulated, respectively. We observed that the entire flagellar and chemotaxis gene regulons were highly upregulated. Furthermore, the flagella master regulator encoded by flhD was the most highly differentially expressed gene in the comparison. Interestingly, the expression of several proteins related to the metabolism of the second messenger c-di-GMP was significantly increased in Bb bvgR-, suggesting that BvgR might be capable of regulating phenotypes through the manipulation of c-di-GMP levels. Additionally, several transcriptional regulators, chaperons and heatshock proteins were differently expressed between the strains.The analysis also revealed 98 genes with higher expression in Bb WT than in Bb bvgR- , including bipA and the 14 genes encoding for Type Three Secretion System (TTSS) proteins. qRT-PCR and western blots confirmed these data. The RNAseq analysis suggests BvgR regulates a complex network of genes includingmotility, TTSS as well as other uncharacterized genes. In future studies we will further characterize the downstream regulatory networks controlled by BvgR.