CONICET | Buscador de Institutos y Recursos Humanos

Small RNAs (sRNAs) have been recognized for being important gene regulators in bacteria. sRNAs play several essential roles in multiple cellular processes, including abiotic and biotic stress response. The majority of sRNAs regulate their target genes by base pairing, affecting mRNA stability and/or translation and the activity of proteins. The Sm-like Hfq protein is a key factor in the processes regulated by RNAs that promotes the sRNAs and mRNA interaction. The Hfq deficiency has a great impact in the physiology of several bacteria and was reported it is involved in the virulence processes in many animal pathogens. However, little is known about sRNAs and Hfq protein in bacterial plant pathogens. Xanthomonas citri subsp. citri (Xcc) is the bacterium responsible of citrus canker A, a severe disease that affects most commercial citrus cultivars worldwide. The aim of this work was the study of the role of Hfq protein in the bacterial physiology and in the pathogenesis process during citrus canker. For that purpose we have constructed the knockout hfq (XccΔhfq) and the complementant strains. Swimming and swarming assays, performed in XVM2-0.3 or 0.7% agar plates and biofilm formation, evaluated by confocal microscopy of GFP expressing strains, indicated that the Hfq protein from Xcc could be implicated in the control of these features. Lower survival rate for the mutant strain was observed after hydrogen peroxide treatment. In addition, XccΔhfq showed lower levels of catalase and superoxide dismutase activity in non-denaturing polyacrylamide gels. On the other hand, higher Hfq protein expression was observed in bacteria cultured in XVM2, a minimum medium that simulates conditions in the apoplastic space of plants. In addition, a reduction in the disease symptoms was observed in orange leaves inoculated with XccΔhfq. These results suggest a role of Hfq protein in the regulation of sRNAs involved in bacterial virulence during citrus canker disease.