title: Origins of the Xylella fastidiosa prophage-like regions and their impact in genome differentiation.
abstract: Xylella fastidiosa is a Gram negative plant pathogen causing many economically important diseases, and analyses of completely sequenced X. fastidiosa genome strains allowed the identification of many prophage-like elements and possibly phage remnants, accounting for up to 15% of the genome composition. To better evaluate the recent evolution of the X. fastidiosa chromosome backbone among distinct pathovars, the number and location of prophage-like regions on two finished genomes (9a5c and Temecula1), and in two candidate molecules (Ann1 and Dixon) were assessed. Based on comparative best bidirectional hit analyses, the majority (51%) of the predicted genes in the X. fastidiosa prophage-like regions are related to structural phage genes belonging to the Siphoviridae family. Electron micrograph reveals the existence of putative viral particles with similar morphology to lambda phages in the bacterial cell in planta. Moreover, analysis of microarray data indicates that 9a5c strain cultivated under stress conditions presents enhanced expression of phage anti-repressor genes, suggesting switches from lysogenic to lytic cycle of phages under stress-induced situations. Furthermore, virulence-associated proteins and toxins are found within these prophage-like elements, thus suggesting an important role in host adaptation. Finally, clustering analyses of phage integrase genes based on multiple alignment patterns reveal they group in five lineages, all possessing a tyrosine recombinase catalytic domain, and phylogenetically close to other integrases found in phages that are genetic mosaics and able to perform generalized and specialized transduction. Integration sites and tRNA association is also evidenced. In summary, we present comparative and experimental evidence supporting the association and contribution of phage activity on the differentiation of Xylella genomes.
authors.affiliation: Genome and Transposable Elements Laboratory (GaTE Lab), Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Alessandro
authors.initials: A
authors.lastname: de Mello Varani
authors.forename: Rangel Celso
authors.initials: RC
authors.lastname: Souza
authors.forename: Helder I
authors.initials: HI
authors.lastname: Nakaya
authors.forename: Wanessa Cristina
authors.initials: WC
authors.lastname: de Lima
authors.forename: Luiz Gonzaga
authors.initials: LG
authors.lastname: Paula de Almeida
authors.forename: Elliot Watanabe
authors.initials: EW
authors.lastname: Kitajima
authors.forename: Jianchi
authors.initials: J
authors.lastname: Chen
authors.forename: Edwin
authors.initials: E
authors.lastname: Civerolo
authors.forename: Ana Tereza Ribeiro
authors.initials: AT
authors.lastname: Vasconcelos
authors.forename: Marie-Anne
authors.initials: MA
authors.lastname: Van Sluys
mesh_terms: D019143:Evolution, Molecular; D005798:Genes, Bacterial; D014644:Genetic Variation; D016680:Genome, Bacterial / Q000235:genetics*; D016679:Genome, Viral / Q000235:genetics*; D019426:Integrases / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D016366:Open Reading Frames / Q000235:genetics; D010802:Phylogeny; D039002:Prophages / Q000235:genetics*; D012343:RNA, Transfer / Q000235:genetics / Q000378:metabolism; D044167:Xylella / Q000145:classification / Q000235:genetics* / Q000254:growth & development
chemical_list: D012343:RNA, Transfer; D019426:Integrases