title: Loss of virulence of the phytopathogen Ralstonia solanacearum through infection by φRSM filamentous phages.
abstract: φRSM1 and φRSM3 (φRSM phages) are filamentous phages (inoviruses) that infect Ralstonia solanacearum, the causative agent of bacterial wilt. Infection by φRSM phages causes several cultural and physiological changes to host cells, especially loss of virulence. In this study, we characterized changes related to the virulence in φRSM3-infected cells, including (i) reduced twitching motility and reduced amounts of type IV pili (Tfp), (ii) lower levels of β-1,4-endoglucanase (Egl) activity and extracellular polysaccharides (EPS) production, and (iii) reduced expression of certain genes (egl, pehC, phcA, phcB, pilT, and hrpB). The significantly lower levels of phcA and phcB expression in φRSM3-infected cells suggested that functional PhcA was insufficient to activate many virulence genes. Tomato plants injected with φRSM3-infected cells of different R. solanacearum strains did not show wilting symptoms. The virulence and virulence factors were restored when φRSM3-encoded orf15, the gene for a putative repressor-like protein, was disrupted. Expression levels of phcA as well as other virulence-related genes in φRSM3-ΔORF15-infected cells were comparable with those in wild-type cells, suggesting that orf15 of φRSM3 may repress phcA and, consequently, result in loss of virulence.
authors.affiliation: Department of Molecular Biotechnology, Hiroshima University, Higashi-Hiroshima, Japan.
authors.forename: Hardian S
authors.initials: HS
authors.lastname: Addy
authors.forename: Ahmed
authors.initials: A
authors.lastname: Askora
authors.forename: Takeru
authors.initials: T
authors.lastname: Kawasaki
authors.forename: Makoto
authors.initials: M
authors.lastname: Fujie
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamada
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D036781:Fimbriae Proteins / Q000235:genetics; D010861:Fimbriae, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics; D005814:Genes, Viral / Q000235:genetics*; D017912:Inovirus / Q000235:genetics / Q000502:physiology*; D018551:Solanum lycopersicum / Q000382:microbiology*; D010935:Plant Diseases / Q000382:microbiology*; D011135:Polysaccharides, Bacterial / Q000378:metabolism; D043368:Ralstonia solanacearum / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology / Q000821:virology; D014774:Virulence / Q000235:genetics; D037521:Virulence Factors / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D011135:Polysaccharides, Bacterial; D037521:Virulence Factors; D036781:Fimbriae Proteins