BVGR REGULATES THE TRANSCRIPTION OF A WIDE VARIETY OF GENES IN BORDETELLA BRONCHISEPTICA, INCLUDING VIRULENCE FACTORS

SEN-KILIC, E; SISTI, FEDERICO; GUTIÉRREZ, MARÍA DE LA PAZ; DAMRON, FH; WONG, TING; FERNANDEZ, JULIETA

Salta

Congreso; LV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2019

SAIB y PABMB

Bordetella bronchiseptica (Bb) is a pathogenic bacterium that causes respiratory infections in animals. Bb virulence factors are regulated byseveral mechanisms, being the most well-characterized the Bordetella three component system, BvgASR. When this system is active, theresponse regulator BvgA activates the expression of virulence-activated genes. On the contrary, BvgR represses the transcription of somevirulence-repressed genes, such as Bb flagellin. No DNA binding domain has been described for BvgR. To date, microarray analyses have beenused to identify some genes controlled by BvgR but the totality of the genes regulated by BvgR is unknown. In order to characterize more deeplythe BvgR regulon, we performed RNA seq on RNA samples from a wild type Bb (Bb WT) and a mutant in bvgR (Bb bvgR-). Comparing thebvgR mutant to the wild type revealed differential expression of 319 genes, of which 221 and 98 were upregulated or downregulated,respectively. Among the upregulated genes we could detect the entire flagellar and chemotaxis genes regulons; the flagella master regulatorencoded by flhD was the most highly upregulated gene. In addition, several transcriptional regulators, chaperons, heat shock proteins andproteins related to the second messenger c-di-GMP metabolism were found differently expressed between the strains.The transcriptomic analysisalso revealed 98 genes with higher expression in Bb WT than in Bb BvgR-, some of which encoded for virulence factors such as bipA and TypeThree Secretion System proteins. qRT-PCR and western blots confirmed these data. In order to evaluate the impact of the downregulation of theTTSS on Bb bvgR-, cytotoxicity assays on J774 macrophages were performed. A decrease in the percent LDH release induced by Bb bvgRconfirmed that this strain is less cytotoxic than Bb WT. Altogether, these data indicate that BvgR regulates a complex network of genes anddifferent phenotypes such as motility and cytotoxicity. In future studies we will further characterize the downstream regulatory networkscontrolled by BvgR.