title: What Drives Positive Selection in theDrosophilapiRNA Machinery? The Genomic Autoimmunity Hypothesis.
abstract: In animals, PIWI-interacting RNAs (piRNAs) play a crucial role in genome defense. Moreover, because piRNAs can be maternally transmitted, they contribute to the epigenetic profile of inheritance. Multiple studies, especially inDrosophila, have demonstrated that the machinery of piRNA biogenesis is often the target of positive selection. Because transposable elements (TEs) are a form of genetic parasite, positive selection in the piRNA machinery is often explained by analogy to the signatures of positive selection commonly observed in genes that play a role in host-parasite dynamics. However, the precise mechanisms that drive positive selection in the piRNA machinery are not known. In this review, we outline several mechanistic models that might explain pervasive positive selection in the piRNA machinery ofDrosophilaspecies. We propose that recurrent positive selection in the piRNA machinery can be partly explained by an ongoing tension between selection for sensitivity required by genome defense and selection for specificity to avoid the off-target effects of maladaptive genic silencing by piRNA.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS.
authors.forename: Justin P
authors.initials: JP
authors.lastname: Blumenstiel
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS.
authors.forename: Alexandra A
authors.initials: AA
authors.lastname: Erwin
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS.
authors.forename: Lucas W
authors.initials: LW
authors.lastname: Hemmer
mesh_terms: D000818:Animals; D015551:Autoimmunity / Q000235:genetics / Q000502:physiology; D004251:DNA Transposable Elements / Q000235:genetics; D004330:Drosophila; D044127:Epigenesis, Genetic / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics*
chemical_list: D004251:DNA Transposable Elements; D034741:RNA, Small Interfering
keywords: Red Queen; host-parasite; piRNA; positive selection; selfish elements; transposable element