RT Journal Article SR Electronic T1 Endogenous giant viruses contribute to intraspecies genomic variability in the model green alga Chlamydomonas reinhardtii JF bioRxiv FD Cold Spring Harbor Laboratory SP 2021.11.30.470594 DO 10.1101/2021.11.30.470594 A1 Mohammad Moniruzzaman A1 Frank O. Aylward YR 2022 UL http://biorxiv.org/content/early/2022/03/17/2021.11.30.470594.abstract AB Chlamydomonas reinhardtii is an important eukaryotic alga that has been studied as a model organism for decades. Despite extensive history as a model system, phylogenetic and genetic characteristics of viruses infecting this alga have remained elusive. We analyzed high-throughput genome sequence data of C. reinhardtii field isolates, and in six we discovered sequences belonging to endogenous giant viruses that reach up to several hundred kilobases in length. In addition, we have also discovered the entire genome of a closely related giant virus that is endogenized within the genome of Chlamydomonas incerta, the closest sequenced phylogenetic relatives of C. reinhardtii. Endogenous giant viruses add hundreds of new gene families to the host strains, highlighting their contribution to the pangenome dynamics and inter-strain genomic variability of C. reinhardtii. Our findings suggest that the endogenization of giant viruses can have important implications for structuring the population dynamics and ecology of protists in the environment.Competing Interest StatementThe authors have declared no competing interest.