title: The RNA-binding protein CsrA plays a central role in positively regulating virulence factors in Erwinia amylovora.
abstract: The GacS/GacA two-component system (also called GrrS/GrrA) is a global regulatory system which is highly conserved among gamma-proteobacteria. This system positively regulates non-coding small regulatory RNA csrB, which in turn binds to the RNA-binding protein CsrA. However, how GacS/GacA-Csr system regulates virulence traits in E. amylovora remains unknown. Results from mutant characterization showed that the csrB mutant was hypermotile, produced higher amount of exopolysaccharide amylovoran, and had increased expression of type III secretion (T3SS) genes in vitro. In contrast, the csrA mutant exhibited complete opposite phenotypes, including non-motile, reduced amylovoran production and expression of T3SS genes. Furthermore, the csrA mutant did not induce hypersensitive response on tobacco or cause disease on immature pear fruits, indicating that CsrA is a positive regulator of virulence factors. These findings demonstrated that CsrA plays a critical role in E. amylovora virulence and suggested that negative regulation of virulence by GacS/GacA acts through csrB sRNA, which binds to CsrA and neutralizes its positive effect on T3SS gene expression, flagellar formation and amylovoran production. Future research will be focused on determining the molecular mechanism underlying the positive regulation of virulence traits by CsrA.
authors.affiliation: Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urban 61801, USA.
authors.forename: Veronica
authors.initials: V
authors.lastname: Ancona
authors.affiliation: Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urban 61801, USA.
authors.forename: Jae Hoon
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urban 61801, USA.
authors.forename: Youfu
authors.initials: Y
authors.lastname: Zhao
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D044084:Erwinia amylovora / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity; D009154:Mutation; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D000069296:Type III Secretion Systems / Q000235:genetics / Q000378:metabolism; D037521:Virulence Factors / Q000096:biosynthesis / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D011135:Polysaccharides, Bacterial; D016601:RNA-Binding Proteins; D000069296:Type III Secretion Systems; D037521:Virulence Factors; C100769:amylovoran