The Ancient Evolutionary History of Polyomaviruses
Fig 5
A hypothetical framework for ancient recombination events among major polyomavirus clades.
The model attempts to reconcile observed incongruities between LT and VP1 phylogenetic trees shown in Figs 3 and 4. In the model, a hypothetical ancient polyomavirus, designated Arche, is inferred to have infected the last common ancestor of bilaterian animals. The ancient Arche lineage then gave rise to separate polyomavirus lineages found in arthropods and fish, as well as the mammalian Ortho/Almi lineages. The figure depicts Avi and Wuki clades arising after recombination events involving an unknown vertebrate-Arche lineage and Ortho-like species. The figure does not depict the inferred evolution of the HPyV6/7 clade, which appears to have arisen after a separate recombination event involving the late region of a hypothetical vertebrate-Arche lineage and the early region of a basal Almi-like species. The TSV lineage, which shows evidence of recombination between the Ortho and Almi lineages, is also omitted. White lollipops represent predicted pRb-binding motifs (LXCXE or related sequences). Yellow bars represent hypothetical metal-binding motifs (CXCXXC or related sequences). The absence of metal-binding motifs in Avi small T antigen (sT) proteins suggests a different evolutionary origin than the classic metal-binding Ortho/Almi sT. Possible ALTO-like ORFs predicted for some Ortho species are shaded gray.