Genetic variability and evolutionary dynamics of viruses of the family Closteroviridae

Abstract

RNA viruses have a great potential for genetic variation, rapid evolution and adaptation. Characterization of the genetic variation of viral populations provides relevant information on the processes involved in virus evolution and epidemiology and it is crucial for designing reliable diagnostic tools and developing efficient and durable disease control strategies. Here we performed an updated analysis of sequences available in Genbank and reviewed present knowledge on the genetic variability and evolutionary processes of viruses of the family Closteroviridae. Several factors have shaped the genetic structure and diversity of closteroviruses. (I) A strong negative selection seems to be responsible for the high genetic stability in space and time for some viruses. (2) Long distance migration, probably by human transport of infected propagative plant material, have caused that genetically similar virus isolates are found in distant geographical regions. (3) Recombination between divergent sequence variants have generated new genotypes and plays an important role for the evolution of some viruses of the family Closteroviridae. (4) Interaction between virus strains or between different viruses in mixed infections may alter accumulation of certain strains. (5) Host change or virus transmission by insect vectors induced changes in the viral population structure due to positive selection of sequence variants with higher fitness for host-virus or vector-virus interaction (adaptation) or by genetic drift due to random selection of sequence variants during the population bottleneck associated to the transmission process.

Keywords: Ampelovirus; Closterovirus; Crinivirus; gene flow; phylogeny; recombination; selection.

Figure 1

Neighbor-joining phylogenetic trees of the coat protein genes of different viruses of the family Closteroviridae. Bootstrap values higher than 0.75 are indicated with asterisks. Two-letter codes indicate countries (defined in ISO 3166-1) and/or US states. Numbers preceding the codes indicate the number of isolates analyzed from each country. For each virus, genetic groups are indicated in gray boxes with Roman numerals and include virus isolates having nucleotide distances higher than 0.1 with all isolates from other clades. Subgroups or clades in CTV are indicated in darker boxes with Arabic numbers. (A) Genus Ampelovirus, (B) Genus Crinivirus, and (C) genus Closterovirus.