title: Contribution of recombination and selection to molecular evolution of Citrus tristeza virus.
abstract: The genetic variation of Citrus tristeza virus (CTV) was analysed by comparing the predominant sequence variants in seven genomic regions (p33, p65, p61, p18, p13, p20 and p23) of 18 pathogenically distinct isolates from seven different countries. Analyses of the selective constraints acting on each codon suggest that most regions were under purifying selection. Phylogenetic analysis shows diverse patterns of molecular evolution for different genomic regions. A first clade composed of isolates that are genetically close to the reference mild isolates T385 or T30 was inferred from all genomic regions. A second clade, mostly comprising virulent isolates, was defined from regions p33, p65, p13 and p23. For regions p65, p61, p18, p13 and p23, a third clade that mostly included South American isolates could not be related to any reference genotype. Phylogenetic relationships among isolates did not reflect their geographical origin, suggesting significant gene flow between geographically distant areas. Incongruent phylogenetic trees for different genomic regions suggested recombination events, an extreme that was supported by several recombination-detecting methods. A phylogenetic network incorporating the effect of recombination showed an explosive radiation pattern for the evolution of some isolates and also grouped isolates by virulence. Taken together, the above results suggest that negative selection, gene flow, sequence recombination and virulence may be important factors driving CTV evolution.
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas (CSIC-UPV), 46022 Valencia, Spain.|Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias, Moncada, 46113 Valencia, Spain.
authors.forename: Susana
authors.initials: S
authors.lastname: Martín
authors.affiliation: Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias, Moncada, 46113 Valencia, Spain.
authors.forename: Adrián
authors.initials: A
authors.lastname: Sambade
authors.affiliation: Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias, Moncada, 46113 Valencia, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Rubio
authors.affiliation: Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias, Moncada, 46113 Valencia, Spain.
authors.forename: María C
authors.initials: MC
authors.lastname: Vives
authors.affiliation: Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias, Moncada, 46113 Valencia, Spain.
authors.forename: Patricia
authors.initials: P
authors.lastname: Moya
authors.affiliation: Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias, Moncada, 46113 Valencia, Spain.
authors.forename: José
authors.initials: J
authors.lastname: Guerri
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas (CSIC-UPV), 46022 Valencia, Spain.
authors.forename: Santiago F
authors.initials: SF
authors.lastname: Elena
authors.affiliation: Centro de Protección Vegetal y Biotecnología, Instituto Valenciano de Investigaciones Agrarias, Moncada, 46113 Valencia, Spain.
authors.forename: Pedro
authors.initials: P
authors.lastname: Moreno
mesh_terms: D002957:Citrus / Q000821:virology*; D017790:Closterovirus / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D016000:Cluster Analysis; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D010935:Plant Diseases / Q000821:virology; D011110:Polymorphism, Genetic; D012367:RNA, Viral / Q000235:genetics*; D011995:Recombination, Genetic; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA
chemical_list: D012367:RNA, Viral