title: Comparative Genomic Analyses of Multiple Pseudomonas Strains Infecting Corylus avellana Trees Reveal the Occurrence of Two Genetic Clusters with Both Common and Distinctive Virulence and Fitness Traits.
abstract: The European hazelnut (Corylus avellana) is threatened in Europe by several pseudomonads which cause symptoms ranging from twig dieback to tree death. A comparison of the draft genomes of nine Pseudomonas strains isolated from symptomatic C. avellana trees was performed to identify common and distinctive genomic traits. The thorough assessment of genetic relationships among the strains revealed two clearly distinct clusters: P. avellanae and P. syringae. The latter including the pathovars avellanae, coryli and syringae. Between these two clusters, no recombination event was found. A genomic island of approximately 20 kb, containing the hrp/hrc type III secretion system gene cluster, was found to be present without any genomic difference in all nine pseudomonads. The type III secretion system effector repertoires were remarkably different in the two groups, with P. avellanae showing a higher number of effectors. Homologue genes of the antimetabolite mangotoxin and ice nucleation activity clusters were found solely in all P. syringae pathovar strains, whereas the siderophore yersiniabactin was only present in P. avellanae. All nine strains have genes coding for pectic enzymes and sucrose metabolism. By contrast, they do not have genes coding for indolacetic acid and anti-insect toxin. Collectively, this study reveals that genomically different Pseudomonas can converge on the same host plant by suppressing the host defence mechanisms with the use of different virulence weapons. The integration into their genomes of a horizontally acquired genomic island could play a fundamental role in their evolution, perhaps giving them the ability to exploit new ecological niches.
authors.affiliation: Consiglio per la ricerca in agricoltura e l'analisi dell'economia agraria (C.R.A.)-Centro di Ricerca per la Frutticoltura, Via di Fioranello 52, I-00134, Roma, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Marcelletti
authors.affiliation: Consiglio per la ricerca in agricoltura e l'analisi dell'economia agraria (C.R.A.)-Centro di Ricerca per la Frutticoltura, Via di Fioranello 52, I-00134, Roma, Italy; Consiglio per la ricerca in agricoltura e l'analisi dell'economia agraria (C.R.A.)-Unità di Ricerca per la Frutticoltura, Via Torrino 3, I-81100, Caserta, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Scortichini
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D001482:Base Composition; D064112:Clustered Regularly Interspaced Short Palindromic Repeats; D060085:Coinfection; D055028:Comparative Genomic Hybridization; D031211:Corylus / Q000382:microbiology*; D004269:DNA, Bacterial / Q000235:genetics; D005060:Europe; D019143:Evolution, Molecular; D051456:Gene Flow; D022761:Gene Transfer, Horizontal; D005798:Genes, Bacterial; D056084:Genetic Fitness; D049810:Genetic Speciation; D044404:Genomic Islands / Q000235:genetics*; D054884:Host-Pathogen Interactions / Q000235:genetics; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology*; D011549:Pseudomonas / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D011995:Recombination, Genetic; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity; D014774:Virulence / Q000235:genetics
chemical_list: D004269:DNA, Bacterial