PT - JOURNAL ARTICLE AU - Atma M. Ivancevic AU - R. Daniel Kortschak AU - Terry Bertozzi AU - David L. Adelson TI - LINES between species: Evolutionary dynamics of LINE-1 retrotransposons across the eukaryotic tree of life AID - 10.1101/050880 DP - 2016 Jan 01 TA - bioRxiv PG - 050880 4099 - http://biorxiv.org/content/early/2016/04/28/050880.short 4100 - http://biorxiv.org/content/early/2016/04/28/050880.full AB - LINE-1 (L1) retrotransposons are dynamic elements. They have the potential to cause great genomic change due to their ability to ‘jump’ around the genome and amplify themselves, resulting in the duplication and rearrangement of regulatory DNA. Active L1, in particular, are often thought of as tightly constrained, homologous and ubiquitous elements with well-characterised domain organisation. For the past 30 years, model organisms have been used to define L1s as 6-8kb sequences containing a 5’-UTR, two open reading frames working harmoniously in cis, and a 3’-UTR with a polyA tail.In this study, we demonstrate the remarkable and overlooked diversity of L1s via a comprehensive phylogenetic analysis of over 500 species from widely divergent branches of the tree of life. The rapid and recent growth of L1 elements in mammalian species is juxtaposed against their decline in plant species and complete extinction in most reptiles and insects. In fact, some of these previously unexplored mammalian species (e.g. snub-nosed monkey, minke whale) exhibit L1 retrotranspositional ‘hyperactivity’ far surpassing that of human or mouse. In contrast, non-mammalian L1s have become so varied that the current classification system seems to inadequately capture their structural characteristics. Our findings illustrate how both long-term inherited evolutionary patterns and random bursts of activity in individual species can significantly alter genomes, highlighting the importance of L1 dynamics in eukaryotes.