Telomere‐Specialized Retroelements in Drosophila : Adaptive Symbionts of the Genome, Neutral, or in Conflict?

Linear chromosomes shorten in every round of replication. In Drosophila , telomere‐specialized long interspersed retrotransposable elements (LINEs) belonging to the jockey clade offset this shortening by forming head‐to‐tail arrays at Drosophila telomere ends. As such, these telomeric LINEs have been considered adaptive symbionts of the genome, protecting it from premature decay, particularly as Drosophila lacks a conventional telomerase holoenzyme. However, as reviewed here, recent work reveals a high degree of variation and turnover in the telomere‐specialized LINE lineages across Drosophila . There appears to be no absolute requirement for LINE activity to maintain telomeres in flies, hence the suggestion that the telomere‐specialized LINEs may instead be neutral or in conflict with the host, rather than adaptive.