A transcriptome-wide RNAi screen in the Drosophila ovary reveals factors of the germline piRNA pathway [smallRNA-Seq]
The Drosophila piRNA pathway provides an RNA-based immune system that defends the germline genome against selfish genetic elements. Two inter-related branches of the piRNA system exist: somatic cells that support oogenesis only employ Piwi, whereas germ cells utilize a more elaborated pathway centered on the three gonad-specific Argonaute proteins Piwi, Aubergine, and Argonaute3. While several key factors of each branch have been identified, our current knowledge is insufficient to explain the complex workings of the piRNA machinery. Here, we report a reverse genetic screen spanning the ovarian transcriptome in an attempt to uncover the full repertoire of genes required for piRNA-mediated transposon silencing in the female germline. Our screen reveals new key factors of piRNA-mediated transposon silencing, including the novel piRNA biogenesis factors, CG2183 (GASZ) and Deadlock. Last, our data uncovers a previously unanticipated set of factors preferentially required for repression of different transposons types. Overall design: Examination of small RNA levels from nos-GAL4 or tj-GAL4 driven UAS-dsRNA knockdowns of control genes and piRNA pathway components in ovaries of Drosophila melanogaster by deep sequencing (using Illumina HiSeq2000).