GEOapplication/xmlftp://ftp.ncbi.nlm.nih.gov/geo/series/GSE93nnn/GSE93559/primaryOK2000000GenomicsGallus gallusExpression profiling by high throughput sequencing; Otherhttps://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE93559GEOGSE0falseDomestic chickens activate a piRNA defense against avian leukosis virusPIWI-interacting RNAs (piRNAs) protect the germ line by targeting transposable elements (TEs) through base-pair complementarity. We do not know how piRNAs co-evolve with TEs in chickens. Here we reported that all active TEs in the chicken germ line are targeted by piRNAs, and as TEs lose their activity, the corresponding piRNAs erode away. We observed de novo piRNA birth as host responds to a recent retroviral invasion. Avian leukosis virus (ALV) has endogenized prior to chicken domestication, remains infectious, and threatens poultry industry. Domestic fowl produced piRNAs targeting ALV from a genomic locus that was known to render its host ALV resistant. This genomic locus does not produce piRNAs in undomesticated wild chickens. Our findings uncover rapid piRNA evolution reflecting contemporary TE activity, identify a new piRNA acquisition modality by activating a pre-existing genomic locus, and extend piRNA defense roles to include the period when endogenous retroviruses are still infectious.2017/04/07GSE93559GSM2454693GSM245469216133SRP09669493559Gallus gallus[28384097]