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bioRxiv2019

Evolution of the PRD1-adenovirus lineage: a viral tree of life incongruent with the cellular universal tree of life

Double-stranded DNA viruses of the PRD1-adenovirus lineage are characterized by homologous major capsid proteins containing one or two {beta}-barrel domains known as the jelly roll folds. Most of them also share homologous packaging ATPases of the FtsK/HerA superfamily P-loop ATPases. Remarkably, members of this lineage infect hosts from the three domains of life, suggesting that viruses from this lineage could be very ancient and share a common ancestor. Here we analyzed the evolutionary history of these cosmopolitan viruses by inferring phylogenies based on single or concatenated genes. These viruses can be divided into two supergroups infecting either eukaryotes or prokaryotes. The latter can be further divided into two groups of bacterioviruses and one group of archaeoviruses. This viral tree is thus incongruent with the cellular tree of life in which Archaea are closer to Eukarya and more divergent from Bacteria. We discuss various evolutionary scenarios that could explain this paradox.

evolutionary biology↗

bioRxiv2018

Diversification of giant and large eukaryotic dsDNA viruses predated the origin of modern eukaryotes

Giant and large eukaryotic double-stranded DNA viruses from the Nucleo-Cytoplasmic Large DNA Virus (NCLDV) assemblage represent a remarkably diverse and potentially ancient component of the eukaryotic virome. However, their origin(s), evolution and potential roles in the emergence of modern eukaryotes remain a subject of intense debate. Since the characterization of the mimivirus in 2003, many big and giant viruses have been discovered at a steady pace, offering a vast material for evolutionary investigations. In parallel, phylogenetic tools are constantly being improved, offering more rigorous approaches for reconstruction of deep evolutionary history of viruses and their hosts. Here we present robust phylogenetic trees of NCLDVs, based on the 8 most conserved proteins responsible for virion morphogenesis and informational processes. Our results uncover the evolutionary relationships between different NCLDV families and support the existence of two superclades of NCLDVs, each encompassing several families. We present evidence strongly suggesting that the NCLDV core genes, which are involved in both informational processes and virion formation, were acquired vertically from a common ancestor. Among them, the largest subunits of the DNA-dependent RNA polymerase were seemingly transferred from two clades of NCLDVs to proto-eukaryotes, giving rise to two of the three eukaryotic DNA-dependent RNA polymerases. Our results strongly suggest that these transfers and the diversification of NCLDVs predated the emergence of modern eukaryotes, emphasizing the major role of viruses in the evolution of cellular domains.

evolutionary biology↗