Telomeric TART elements target the piRNA machinery in Drosophila

Abstract

Coevolution between transposable elements (TEs) and their hosts can be antagonistic, where TEs evolve to avoid silencing and the host responds by reestablishing TE suppression, or mutualistic, where TEs are co-opted to benefit their host. TheTART-ATE functions as an important component ofDrosophilatelomeres but has also reportedly inserted into theDrosophila melanogasternuclear export factor genenxf2. We find that, rather than inserting intonxf2,TART-Ahas actually captured a portion ofnxf2sequence. We show thatTART-Aproduces abundant Piwi-interacting small RNAs (piRNAs), some of which are antisense to thenxf2transcript, and that theTART-like region ofnxf2is evolving rapidly. Furthermore, inD.melanogaster,TART-Ais present at higher copy numbers, andnxf2shows reduced expression, compared to the closely related speciesDrosophila simulans. We propose that capturingnxf2sequence allowedTART-Ato target thenxf2gene for piRNA-mediated repression and that these 2 elements are engaged in antagonistic coevolution despite the fact thatTART-Ais serving a critical role for its host genome.