title: Transcriptome profiling of a Rhizobium leguminosarum bv. trifolii rosR mutant reveals the role of the transcriptional regulator RosR in motility, synthesis of cell-surface components, and other cellular processes.
abstract: BACKGROUND
  Rhizobium leguminosarum bv. trifolii is a soil bacterium capable of establishing a symbiotic relationship with red clover (Trifolium pratense). The presence of surface polysaccharides and other extracellular components as well as motility and competitiveness are essential traits for both adaptation of this bacterium to changing environmental conditions and successful infection of host plant roots. The R. leguminosarum bv. trifolii rosR gene encodes a protein belonging to the family of Ros/MucR transcriptional regulators, which contain a Cys2His2-type zinc-finger motif and are involved in the regulation of exopolysaccharide synthesis in several rhizobial species. Previously, it was established that a mutation in the rosR gene significantly decreased exopolysaccharide synthesis, increased bacterial sensitivity to some stress factors, and negatively affected infection of clover roots.
  
  
  RESULTS
  RNA-Seq analysis performed for the R. leguminosarum bv. trifolii wild-type strain Rt24.2 and its derivative Rt2472 carrying a rosR mutation identified a large number of genes which were differentially expressed in these two backgrounds. A considerable majority of these genes were up-regulated in the mutant (63.22 %), indicating that RosR functions mainly as a repressor. Transcriptome profiling of the rosR mutant revealed a role of this regulator in several cellular processes, including the synthesis of cell-surface components and polysaccharides, motility, and bacterial metabolism. Moreover, it was established that the Rt2472 strain was characterized by a longer generation time and showed an increased aggregation ability, but was impaired in motility as a result of considerably reduced flagellation of its cells.
  
  
  CONCLUSIONS
  The comparative transcriptome analysis of R. leguminosarum bv. trifolii wild-type Rt24.2 and the Rt2472 mutant identified a set of genes belonging to the RosR regulon and confirmed the important role of RosR in the regulatory network. The data obtained in this study indicate that this protein affects several cellular processes and plays an important role in bacterial adaptation to environmental conditions.
authors.affiliation: Department of Genetics and Microbiology, Institute of Microbiology and Biotechnology, Maria Curie-Skłodowska University, Akademicka 19, 20-033, Lublin, Poland.
authors.forename: Kamila
authors.initials: K
authors.lastname: Rachwał
authors.affiliation: Department of Mathematics and Computer Science, Institute of Computer Science, Jagiellonian University, Łojasiewicza 6, 30-348, Cracow, Poland.|Genomed SA, Ponczowa 12, 02-971, Warsaw, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Matczyńska
authors.affiliation: Department of Genetics and Microbiology, Institute of Microbiology and Biotechnology, Maria Curie-Skłodowska University, Akademicka 19, 20-033, Lublin, Poland. mon.jan@poczta.umcs.lublin.pl.
authors.forename: Monika
authors.initials: M
authors.lastname: Janczarek
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D029902:Medicago / Q000382:microbiology*; D011135:Polysaccharides, Bacterial / Q000235:genetics / Q000378:metabolism; D016961:Rhizobium leguminosarum / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D011135:Polysaccharides, Bacterial; D014157:Transcription Factors