A phylogenomic data-driven exploration of viral origins and evolution

Nasir, Arshan; Caetano-Anollés, Gustavo

Viral supergroup behaves similarly to cellular superkingdoms in terms of FSF sharing patterns A total of 1995 significant FSF domains (E < 0.0001) were detected iñ 11 million proteins of 5080 proteomes sampled from cells and viruses. A four-set Venn diagram showed that roughly two-thirds of the total FSFs (1279 of 1995) were detected only in cellular proteomes (that is, A, B, E, AB, AE, BE, and ABE Venn groups), whereas the remaining FSFs (716) either were shared between cells and viruses, represented by "XV" Venn groups (that is, AV, BV, EV, ABV, AEV, BEV, and ABEV), or were unique to viruses (V) (Fig. 1A) . Viruses shared FSFs with each and every Venn group (that is, there were no zeros), indicating that Venn diagrams can be extended to include four groups, instead of three, without any oddities. The most populated Venn groups of universal FSFs found in both cells and viruses (ABEV) or shared by Archaea, Bacteria, and Eukarya (ABE) had 442 and 457 FSFs, respectively. The large size of the ABEV group, which is one-fifth of the total FSFs (442), suggests the coexistence of ancient viruses and cells, very much like the large size of ABE strengthening the hypothesis of a common origin of modern cells.