Functional characterization of a global virulence regulator Hfq and identification of Hfq-dependent sRNAs in the plant pathogen Pantoea ananatis
Abstract
To successfully infect plant hosts, the collective regulation of virulence factors in a bacterial pathogen is crucial. Hfq is an RNA chaperone protein that facilitates the small RNA (sRNA) regulation of global gene expression at the post-transcriptional level. In this study, the functional role of Hfq in a broad host range phytopathogen <i>Pantoea ananatis</i> was determined. Inactivation of the <i>hfq</i> gene in <i>P. ananatis</i> LMG 2665<sup>T</sup> resulted in the loss of pathogenicity and motility. In addition, there was a significant reduction of quorum sensing signal molecule acyl-homoserine lactone (AHL) production and biofilm formation. Differential sRNA expression analysis between the <i>hfq</i> mutant and wild-type strains of <i>P. ananatis</i> revealed 276 sRNAs affected in their abundance by the loss of <i>hfq</i> at low (OD<sub>600</sub> = 0.2) and high cell (OD<sub>600</sub> = 0.6) densities. Further analysis identified 25 Hfq-dependent sRNAs, all showing a predicted Rho-independent terminator of transcription and mapping within intergenic regions of the <i>P. ananatis</i> genome. These included known sRNAs such as ArcZ, FnrS, GlmZ, RprA, RyeB, RyhB, RyhB2, Spot42, and SsrA, and 16 novel <i>P. ananatis</i> sRNAs. The current study demonstrated that Hfq is an important component of the collective regulation of virulence factors and sets a foundation for understanding Hfq-sRNA mediated regulation in the phytopathogen <i>P. ananatis</i>.