title: Insights into the diversity of φRSM phages infecting strains of the phytopathogen Ralstonia solanacearum complex: regulation and evolution.
abstract: The filamentous φRSM phages (φRSM1 and φRSM3) have integration/excision capabilities in the phytopathogenic bacterium Ralstonia solanacearum. In the present study, we further investigated φRSM-like sequences present in the genomes of R. solanacearum strains belonging to the four major evolutionary lineages (phylotypes I-IV). Based on bioinformatics and comparative genomic analyses, we found that φRSM homologs are highly diverse in R. solanacearum complex strains. We detected an open reading frame (ORF)15 located upstream of the gene for φRSM integrase, which exhibited amino acid sequence similarity to phage repressor proteins. ORF15-encoded protein (a putative repressor) was found to encode a 104-residue polypeptide containing a DNA-binding (helix-turn-helix) domain and was expressed in R. solanacearum lysogenic strains. This suggested that φRSM3-ORF15 might be involved in the establishment and maintenance of a lysogenic state, as well as in phage immunity. Comparison of the putative repressor proteins and their binding sites within φRSM-related prophages provides insights into how these regulatory systems of filamentous phages have evolved and diverged in the R. solanacearum complex. In conclusion, φRSM phages represent a unique group of filamentous phages that are equipped with innate integration/excision (ORF14) and regulatory systems (ORF15).
authors.affiliation: Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, 1-3-1 kagamiyama, Higashi-Hiroshima, 739-8530, Japan, ahmedaskora@yahoo.com.
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: D000595:Amino Acid Sequence; D001287:Attachment Sites, Microbiological; D001483:Base Sequence; D001665:Binding Sites; D019295:Computational Biology; D004279:DNA, Viral / Q000235:genetics; D019143:Evolution, Molecular; D014644:Genetic Variation; D016679:Genome, Viral / Q000235:genetics*; D017912:Inovirus / Q000235:genetics* / Q000502:physiology; D019426:Integrases / Q000235:genetics; D008242:Lysogeny; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010802:Phylogeny; D039002:Prophages / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics; D043368:Ralstonia solanacearum / Q000821:virology*; D016415:Sequence Alignment; D017384:Sequence Deletion; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D004279:DNA, Viral; D012367:RNA, Viral; D014764:Viral Proteins; D019426:Integrases