Scientists Present Evidence for a Billion-Years Arms Race Between Viruses and Their Hosts
Published:25 Jun.2023 Source:eLife
Their study, published today, provides what the editors say are convincing analyses that advance our understanding of the deep evolutionary history of viruses, the interaction between viruses and the first eukaryotes (organisms with cells that include a nucleus), and the diversification of viral lineages.
Barreat and Katzourakis used two hypothesis-testing methods (maximum-likelihood and Bayesian frameworks) to compare the plausibility of the nuclear-escape versus alternative evolutionary scenarios. They focused on four key proteins shared by viruses in this lineage which are involved in the formation of viral capsids: major and minor capsid proteins, DNA-packaging ATPase, and protease. They applied another two methods that use genetic data to estimate rooted phylogenies, to infer the evolutionary trajectory of the different lineages. Then, they assessed whether adenoviruses and NCLDVs descended from a common ancestor, as predicted by the nuclear-escape scenario.
Their analyses revealed strong evidence against a sister relationship between adenoviruses and NCLDVs, as suggested by the nuclear-escape hypothesis. Instead, the findings suggest that adenoviruses descended from a common ancestor with Mavericks, to the exclusion of NCLDVs. At odds with a virophage-first scenario, the researchers found that the most recent common ancestor of Mavericks and adenoviruses was not a virophage. However, their work does not rule out the virophage-first hypothesis completely, making it the one best supported by current phylogenetic analyses.