A phylogenomic data-driven exploration of viral origins and evolution

Nasir, Arshan; Caetano-Anollés, Gustavo

FSF distributions in the viral supergroup are very patchy but highlight a major contribution from RNA viruses Next, we explored how the 716 viral FSFs distributed between viral replicon types (Fig. 4) . Most viral FSFs were only detected in dsDNA viruses (Fig. 4A ). In comparison, proteomes of the ssDNA, ssRNA, dsRNA, and retrotranscribing groups were genetically poor. Roughly, 91% (649 of 716) of the total viral FSFs were unique to a single viral subgroup, and only~9% (67) of the total viral FSFs were shared by more than one subgroup (Fig. 4A ). The number of shared FSFs in each viral subgroup exceeded the number of unique FSFs, except for dsDNA and minus-ssRNA viruses. A seven-set Venn diagram made clear that each viral subgroup shared FSFs with every other subgroup (the sole exception being ssDNA and dsDNA-RT viruses) but did so sparsely (Fig. 4A , Venn diagram). The diagram shows that there was no single FSF common to all viral subgroups (Fig. 4A) . However, it also revealed that the minus-ssRNA and dsDNA groups circumscribed the most widely shared FSFs (traces highlighted in the Venn diagram) ( Table 4 ).