Poster abstracts
Poster number 146 submitted by Benjamin Pursley
Disparate Functions of a Riboswitch at High and Low Cyclic di-GMP in Vibrio cholerae
Benjamin R. Pursley (Department of Microbiology and Molecular Genetics, Michigan State University), Christopher M. Waters (Department of Microbiology and Molecular Genetics, Michigan State University)
Abstract:
Cyclic di-guanosine-monophosphate (c-di-GMP) is a bacterial second messenger signaling molecule that plays a central role in many diverse phenotypes including biofilm formation, motility, cell cycle regulation, and virulence gene expression. In Vibrio cholerae, c-di-GMP mediates the lifestyle transition from a free-living aquatic organism to a human pathogen, although the genetic regulatory changes that underlie this transition are not yet well understood. The Vc2 riboswitch, located upstream of tfoY, a Vibrionaceae-specific gene of unknown function, has remained one of the functionally uncharacterized genetic inputs for c-di-GMP regulation in V. cholerae. We studied the function of Vc2 in vivo at high and low c-di-GMP states and have determined that the Vc2 riboswitch has two separate and distinct functions. At low c-di-GMP, the Vc2 riboswitch is critical for the induction of V. cholerae motility by inducing tfoY expression. Mutations in Vc2 that disrupt c-di-GMP binding also abrogate tfoY induction and reduce V. cholerae motility. Conversely, although tfoY expression is also induced at high c-di-GMP levels, the Vc2 riboswitch does not substantively contribute to downstream gene regulation. Rather, tfoY is transcriptionally upregulated at multiple riboswitch-independent promoters by a c-di-GMP-binding transcriptional activator. The Vc2 riboswitch instead serves to regulate the abundance of an upstream small RNA. This riboswitch aptamer domain is located at the immediate 3'-end of this sRNA and the stability of the transcript is directly correlated to the intracellular concentration of c-di-GMP. We are currently working to understand the mechanism of Vc2-mediated tfoY induction at low c-di-GMP, and we are identifying the regulatory targets of this Vc2 riboswitch sRNA to elucidate its role in global c-di-GMP regulation of V. cholerae.
Keywords: Riboswitch, cyclic-di-GMP, Vibrio cholerae