The DrosophilaTARTtransposon manipulates the piRNA pathway as a counter-defense strategy to limit host silencing

Co-evolution 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 of Drosophila telomeres, but has also reportedly inserted into theD. melanogasternuclear export factor genenxf2. We find that, rather than inserting intonxf2, TART-Ahas actually captured a portion ofnxf2sequence. We show that Nxf2 is involved in suppressingTART-Aactivity via the piRNA pathway and thatTART-Aproduces abundant piRNAs, some of which are antisense to thenxf2transcript. We propose that capturingnxf2sequence allowedTART-Ato target thenxf2gene for piRNA-mediated repression and that these two elements are engaged in antagonistic co-evolution despite the fact thatTART-Ais serving a critical role for its host genome.