title: The stress-related, rhizobial small RNA RcsR1 destabilizes the autoinducer synthase encoding mRNA sinI in Sinorhizobium meliloti.
abstract: Quorum sensing is a cell density-dependent communication system of bacteria relying on autoinducer molecules. During the analysis of the post-transcriptional regulation of quorum sensing in the nitrogen fixing plant symbiont Sinorhizobium meliloti, we predicted and verified a direct interaction between the 5'-UTR of sinI mRNA encoding the autoinducer synthase and a small RNA (sRNA), which we named RcsR1. In vitro, RcsR1 prevented cleavage in the 5'-UTR of sinI by RNase E and impaired sinI translation. In line with low ribosomal occupancy and transcript destabilization upon binding of RcsR1 to sinI, overproduction of RcsR1 in S. meliloti resulted in lower level and shorter half-life of sinI mRNA, and in decreased autoinducer amount. Although RcsR1 can influence quorum sensing via sinI, its level did not vary at different cell densities, but decreased under salt stress and increased at low temperature. We found that RcsR1 and its stress-related expression pattern, but not the interaction with sinI homologs, are conserved in Sinorhizobium, Rhizobium and Agrobacterium. Consistently, overproduction of RcsR1 in S. meliloti and Agrobacterium tumefaciens inhibited growth at high salinity. We identified conserved targets of RcsR1 and showed that most conserved interactions and the effect on growth under salt stress are mediated by the first stem-loop of RcsR1, while its central part is responsible for the species-specific interaction with sinI. We conclude that RcsR1 is an ancient, stress-related riboregulator in rhizobia and propose that it links stress responses to quorum sensing in S. meliloti.
authors.affiliation: a Institute for Microbiology and Molecular Biology, University of Giessen, Heinrich-Buff-Ring Giessen , Germany.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Baumgardt
authors.affiliation: a Institute for Microbiology and Molecular Biology, University of Giessen, Heinrich-Buff-Ring Giessen , Germany.|b Institute of Immunology and Microbiology, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Studnickova 7, Prague 2, and Institute of Microbiology, Academy of Sciences of the Czech Republic, Laboratory of Bioinformatics, Videnska Prague 4 , Czech Republic.
authors.forename: Klára
authors.initials: K
authors.lastname: Šmídová
authors.affiliation: a Institute for Microbiology and Molecular Biology, University of Giessen, Heinrich-Buff-Ring Giessen , Germany.
authors.forename: Helen
authors.initials: H
authors.lastname: Rahn
authors.affiliation: c Institute of Biochemistry, Friedrichstraße Giessen , Germany.
authors.forename: Günter
authors.initials: G
authors.lastname: Lochnit
authors.affiliation: d LOEWE Center for Synthetic Microbiology and Department of Biology, Hans-Meerwein-Straße Marburg , Germany.
authors.forename: Marta
authors.initials: M
authors.lastname: Robledo
authors.affiliation: a Institute for Microbiology and Molecular Biology, University of Giessen, Heinrich-Buff-Ring Giessen , Germany.
authors.forename: Elena
authors.initials: E
authors.lastname: Evguenieva-Hackenberg
mesh_terms: D020121:5' Untranslated Regions; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D017124:Conserved Sequence; D015964:Gene Expression Regulation, Bacterial; D053038:Quorum Sensing; D012329:RNA, Bacterial / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D058727:RNA, Small Untranslated / Q000235:genetics*; D054712:Salinity; D016962:Sinorhizobium meliloti / Q000235:genetics / Q000502:physiology*; D013312:Stress, Physiological; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D020121:5' Untranslated Regions; D001426:Bacterial Proteins; C085427:LuxI protein, Bacteria; D012329:RNA, Bacterial; D012333:RNA, Messenger; D058727:RNA, Small Untranslated; D014157:Transcription Factors
keywords: Agrobacterium; RNA degradation; RNase E; Sinorhizobium; autoinducer synthase; degradosome; quorum sensing; small RNA; stress response