Abstract
BackgroundHfq is a widely conserved bacterial RNA-binding protein which generally mediates the global regulatory activities involv ed in physiological process and virulence. The goal of this study was to characterize the biological function of hfq gene in Xanthomonas axonpodis pv. citri (Xac), the causal agent of citrus canker disease.ResultsAn hfq mutant in Xac was generated by plasmid integration. The loss of hfq resulted in attenuation of bacterial growth, motility and biofilm formation. In addition, the hfq mutation impaired Xac resistance to H2O2 and both high and low pH environments, but did not affect the virulence to citrus. RNA-Seq analyses indicated that Hfq played roles in regulating the expression of 746 genes. In hfq mutant, gene expression related to chemotaxis, secretion system, two-component system, quorum sensing and flagellar assembly were repressed, whereas expression of ribosomal genes were significantly up-regulated. The down-regulated expression of three bacterial chemotaxis related genes and seven flagella genes, which involved in cell growth and biofilm formation, were further validated by RT-qPCR.ConclusionsThe study demonstrated that hfq was involved in multiple biological processes in Xac. The results could serve as initiate points for identifying regulatory sRNAs and genes controlled by Hfq-sRNA interactions in Xac.
Highlights
Hfq is a widely conserved bacterial RNA-binding protein which generally mediates the global regulatory activities involv ed in physiological process and virulence
Liu et al BMC Microbiology (2019) 19:103 (Xoo), X. campestris pv. vesicatoria (Xcv), X. campestris pv. campestris (Xcc) and X. axonpodis pv. citri (Xac) are economical important pathogens among the genus Xanthomonas. hfq is conserved in Xanthomonas spp. and has been investigated in Xoo and Xcv
A cell-counting kit (CCK)-8 assay was conducted to evaulate the cell viability, and the results demonstrated that cell viability was only slightly inhibited in hfq mutant and no significant difference was found between Xac29–1 and hfq mutant (Data not shown)
Summary
Hfq is a widely conserved bacterial RNA-binding protein which generally mediates the global regulatory activities involv ed in physiological process and virulence. The goal of this study was to characterize the biological function of hfq gene in Xanthomonas axonpodis pv. Hfq is conserved in Xanthomonas spp. and has been investigated in Xoo and Xcv. Inactivation of hfq in Xoo affects it growth in complex medium, but does not disrupt its virulence [13]. Hfq gene in Xcv does not involve in virulence [14]. Many Hfq-dependent sRNAs were identified in Xcv, Xcc, and Xoo [15,16,17], their involvements in regulation and virulence function have been poorly characterized. Citri (Xac), the causal agent of citrus canker, is an important bacterial pathogen that severely affects citrus production worldwide. The roles of global regulator hfq and its related sRNAs remain to be determined
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