The role of RNA in virulence
The RNA chaperone Hfq and small regulatory RNAs are key factors in posttranscriptional regulation in bacteria and play an essential role in virulence of a broad spectrum of bacterial pathogens. We have shown that Tohama I Δhfq strain produces decreased amounts of adenylate cyclase toxin and secreted reduced amounts of pertussis toxin. Likewise, expression of autotransporter vag8 and tracheal colonization factor tcfA was strongly reduced in the hfq mutant. Consequently, the hfq mutant was clearly attenuated in the mouse respiratory model of infection as its lethality as well as capacity to colonize mouse lungs was strongly reduced when compared to the wt strain. In the follow up study we characterized the Hfq regulon in bacterial pathogen using an integrative omics approach. Gene expression profiles were analyzed by RNA-seq and protein amounts in cell-associated and cell-free fractions were determined by LC-MS/MS technique.
Comparative analysis of transcriptomic and proteomic data revealed solid correlation considering the role of Hfq in post-transcriptional control of gene expression. Importantly, our study confirmed and further enlightened the role of Hfq in pathogenicity of B. pertussis as it showed that Δhfq strain displays strongly impaired secretion of substrates of T3SS and substantially reduced resistance to serum killing. On the other side, significantly increased production of proteins implicated in transport of important metabolites and essential nutrients observed in the mutant seems to compensate for the physiological defect introduced by the deletion of the hfq gene. The requirement for Hfq suggested that non-coding sRNA might be involved in regulation in B. pertussis virulence. Indeed, our analysis of the primary transcriptome of B. pertussis revealed hundreds of putative sRNAs and several of them were confirmed. One of them, RgtA, represents the first fully characterized regulatory sRNA RgtA in B. pertussis. Abundance of this sRNA is strongly decreased in the absence of the Hfq protein and its expression is modulated by the activities of the two-component regulatory system BvgAS and another response regulator RisA. Furthermore, we identified plausible target gene of RgtA, the glutamate transporter, as well as the mechanism RgtA-dependent riboregulation. We propose that this sRNA is involved in control of transport of glutamate, an important source of carbon and upon infection it assist in adaptation of the pathogen to other sources of energy.