Recurrent gene duplication diversifies genome defense repertoire in Drosophila

摘要: Transposable elements (TEs) comprise large fractions of many eukaryotic genomes and imperil host genome integrity. The combats these challenges by encoding proteins that silence TE activity. Both the introduction new TEs via horizontal transfer sequence evolution requires constant innovation host-encoded silencing machinery to keep pace with TEs. One form is adaptation existing, single-copy genes. Indeed, suppressors replication often harbor signatures positive selection. Such are especially evident in genes piwi-interacting-RNA pathway gene silencing, for example, female germline-restricted silencer, HP1D/Rhino Host can also innovate duplication divergence. However, importance family expansions, contractions, turnover defense has been largely unexplored. Here, we functionally characterize Oxpecker, a young, tandem duplicate HP1D/rhino We demonstrate Oxpecker supports fertility Drosophila melanogaster silences several families incompletely silenced germline. further show that, like at least ten additional, structurally diverse, HP1D/rhino-derived daughter "granddaughter" emerged during short 15-million year period evolution. These young paralogs transcribed primarily germline tissues, where genetic conflict between plays out. Our findings suggest expansion an underappreciated yet potent evolutionary mechanism diversification.