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Title:   Author  item
                                            WARFEL, JASON - Food And Drug Administration(FDA)item
                                            Nicholson, Tracyitem
                                            KELLY, VANESSA - Food And Drug Administration(FDA)item
                                            MERKEL, TOD - Food And Drug Administration(FDA)
  Submitted to: Meeting Abstract
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 8/15/2013
                                    Publication  Date: 9/8/2013
                                    Citation: Warfel, J.M., Nicholson, T.L., Kelly, V.K., Merkel, T.J. 2013. Cyclic di-GMP regulation of the bvg-repressed genes and the orphan response regulator RisA in Bordetella pertussis. 10th International Symposium on Bordetella. p. 24.Interpretive Summary:
                                Technical Abstract: Expression of Bordetella pertussis virulence factors is activated by the BvgAS two-component system. Under modulating growth conditions BvgAS indirectly represses another set of genes through the action of BvgR, a bvg-activated protein. BvgR blocks activation of the response regulator RisA which is the master regulator of the bvg-repressed genes. The cognate sensor kinase RisS is a pseudogene in B. pertussis and to date the mechanisms by which RisA is activated and how BvgR represses its activity are unknown. Here we report that RisA regulation is dependent upon the bacterial second messenger cyclic di-GMP. We identified a gene, designated risX, which encodes a highly active diguanylate cyclase that synthesizes cyclic di-GMP both ectopically in E. coli and as a purified protein. RisX is required for RisA-dependent transcription of the classical bvg-repressed genes as well as novel ris-activated genes identified by microarray. When BvgR and RisX were co-expressed in E. coli, cyclic di-GMP levels decreased compared to cells expressing only RisX suggesting that BvgR is an active phosphodiesterase. Together, our results support a model whereby in the absence of its cognate sensor kinase, the B. pertussis orphan response regulator RisA activates transcription of the bvg-repressed genes through a signaling pathway involving RisX-synthesized cyclic di-GMP while expression of these genes is repressed by the phosphodiesterase BvgR through cyclic di-GMP degradation.


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