Syracuse

Mirusviruses link herpesviruses to giant viruses

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Delmont, Tom O.

Edité par CCSD -

International audience. DNA viruses have a major influence on the ecology and evolution of cellular organisms, but their overall diversity and evolutionary trajectories remain elusive. Recently, we performed a phylogeny-guided genome-resolved metagenomic survey of the sunlit oceans and discovered plankton-infecting relatives of herpesviruses that form a putative new phylum dubbed ‘Mirusviricota’. The virion morphogenesis module of this large monophyletic clade is typical of viruses from the realm Duplodnaviria, with multiple components strongly indicating a common ancestry with animal-infecting Herpesvirales. Yet, a substantial fraction of mirusvirus genes, including hallmark transcription machinery genes missing in herpesviruses, are closely related homologs of giant eukaryotic DNA viruses from another viral realm. These remarkable chimeric attributes connecting ‘Mirusviricota’ to herpesviruses and giant eukaryotic viruses are supported by a fast-growing number of environmental mirusvirus genomes as well as one culture. Moreover, mirusviruses are among the most abundant and active eukaryotic viruses characterized in the sunlit oceans, encoding a diverse array of functions used during the infection of microbial eukaryotes from pole to pole. The prevalence, functional activity, diversification, and atypical chimeric attributes of mirusviruses point to a lasting role of ‘Mirusviricota’ in the ecology of marine ecosystems and in the evolution of eukaryotic DNA viruses.

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