Genetic diversity and evolution of closteroviruses

The family Closteroviridae comprises more than 30 plant viruses with flexuo us, filamentous virions and includes representatives with either mono- or b ipartite positive-strand ssRNA genomes. Closteroviruses are transmitted sem ipersistently by insects from three families of Homoptera, in infected plan ts are associated with phloem tissue, and demonstrate an astonishing geneti c diversity that suggests extensive, on-going evolution. Phylogenetic analy ses of their replicative genes as well as the conserved HSP70 demonstrate t hat closteroviruses co-evolved with their insect vectors, resulting in thre e major lineages, i.e. aphid-, mealybug-, and whitefly-transmitted viruses. Closteroviruses apparently represent an ancient and diverse virus family t hat may pose threats to agriculture and needs serious attention.