RT Journal Article
SR Electronic
T1 Virophages and retrotransposons colonize the genomes of a heterotrophic flagellate
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2020.11.30.404863
DO 10.1101/2020.11.30.404863
A1 Hackl, Thomas
A1 Duponchel, Sarah
A1 Barenhoff, Karina
A1 Weinmann, Alexa
A1 Fischer, Matthias G.
YR 2021
UL http://biorxiv.org/content/early/2021/08/13/2020.11.30.404863.abstract
AB Virophages can parasitize giant DNA viruses and may provide adaptive anti-giant-virus defense in unicellular eukaryotes. Under laboratory conditions, the virophage mavirus integrates into the nuclear genome of the marine flagellate Cafeteria burkhardae and reactivates upon superinfection with the giant virus CroV. In natural systems, however, the prevalence and diversity of host-virophage associations has not been systematically explored. Here, we report dozens of integrated virophages in four globally sampled C. burkhardae strains that constitute up to 2% of their host genomes. These endogenous mavirus-like elements (EMALEs) separated into eight types based on GC-content, nucleotide similarity, and coding potential and carried diverse promoter motifs implicating interactions with different giant viruses. Between host strains, some EMALE insertion loci were conserved indicating ancient integration events, whereas the majority of insertion sites were unique to a given host strain suggesting that EMALEs are active and mobile. Furthermore, we uncovered a unique association between EMALEs and a group of tyrosine recombinase retrotransposons, revealing yet another layer of parasitism in this nested microbial system. Our findings show that virophages are widespread and dynamic in wild Cafeteria populations, supporting their potential role in antiviral defense in protists.Competing Interest StatementThe authors have declared no competing interest.