From small hosts come big viruses: the complete genome of a second Ostreococcus tauri virus, OtV‐1

<jats:title>Summary</jats:title><jats:p> <jats:italic>Ostreococcus tauri</jats:italic> virus (OtV‐1) is a large double‐stranded DNA virus and a prospective member of the family <jats:italic>Phycodnaviridae</jats:italic>, genus <jats:italic>Prasinovirus</jats:italic>. OtV‐1 infects the unicellular marine green alga <jats:italic>O. tauri</jats:italic>, the smallest known free‐living eukaryote. Here we present the 191 761 base pair genome sequence of OtV‐1, which has 232 putative protein‐encoding and 4 tRNA‐encoding genes. Approximately 31% of the viral gene products exhibit a similarity to proteins of known functions in public databases. These include a variety of unexpected genes, for example, a PhoH‐like protein, a <jats:italic>N</jats:italic>‐myristoyltransferase, a 3‐dehydroquinate synthase, a number of glycosyltransferases and methyltransferases, a prolyl 4‐hydroxylase, 6‐phosphofructokinase and a total of 8 capsid proteins. A total of 11 predicted genes share homology with genes found in the <jats:italic>Ostreococcus</jats:italic> host genome. In addition, an intein was identified in the DNA polymerase gene of OtV‐1. This is the first report of an intein in the genome of a virus that infects <jats:italic>O. tauri.</jats:italic> Fifteen core genes common to nuclear‐cytoplasmic large dsDNA virus (NCLDV) genomes were identified in the OtV‐1 genome. This new sequence data may help to redefine the classification of the core genes of these viruses and shed new light on their evolutionary history.</jats:p>