title: Post-transcriptional activation of a diguanylate cyclase by quorum sensing small RNAs promotes biofilm formation in Vibrio cholerae.
abstract: Biofilms promote attachment of Vibrio cholerae in aquatic ecosystems and aid in transmission. Intracellular c-di-GMP levels that control biofilm development positively correlate with expression of Qrr sRNAs, which are transcribed when quorum sensing (QS) autoinducer levels are low. The Qrr sRNAs base-pair with and repress translation of hapR encoding the QS 'master regulator', hence increased c-di-GMP and biofilm development at low density were believed to be solely a consequence of Qrr/hapR pairing. We show that Qrr sRNAs also base-pair with and activate translation of the mRNA of a diguanylate cyclase (DGC), Vca0939; relieving an inhibitory structure in vca0939 that occludes the ribosome binding site. A nucleotide substitution in vca0939 disrupted sRNA/mRNA base-pairing and prevented vca0939 translation, while a compensating Qrr sRNA substitution restored pairing and Vca0939 levels. Qrr-dependent DGC activation led to c-di-GMP accumulation and biofilm development in V. cholerae. This represents the first description of (1) a DGC post-transcriptionally activated by direct pairing with an Hfq-dependent sRNA, and (2) control of a V. cholerae QS phenotype, independent of HapR. Thus, direct interactions of the same sRNAs with two mRNAs promote c-di-GMP-dependent biofilm formation by complementary mechanisms in V. cholerae; by negatively regulating HapR, and positively regulating the DGC Vca0939.
authors.affiliation: School of Biology, Georgia Institute of Technology, Atlanta, GA, 30332-0230, USA.
authors.forename: Xiaonan
authors.initials: X
authors.lastname: Zhao
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Koestler
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Waters
authors.forename: Brian K
authors.initials: BK
authors.lastname: Hammer
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D009690:Nucleic Acid Conformation; D019761:Phosphorus-Oxygen Lyases / Q000235:genetics / Q000378:metabolism*; D017354:Point Mutation; D014176:Protein Biosynthesis; D053038:Quorum Sensing; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D058727:RNA, Small Untranslated / Q000235:genetics / Q000378:metabolism*; D014734:Vibrio cholerae / Q000235:genetics / Q000502:physiology*
chemical_list: D029968:Escherichia coli Proteins; D012333:RNA, Messenger; D058727:RNA, Small Untranslated; D019761:Phosphorus-Oxygen Lyases; C060720:diguanylate cyclase