piRNA production requires heterochromatin formation in Drosophila

Here, we analyzed H3K9me3 derived from wild type ovarian tissue. Here we show that deposition of histone 3 lysine 9 by the methyltransferase dSETDB1 (egg) is required for piRNA cluster transcription. In the absence of dSETDB1, cluster precursor transcription collapses in germline and somatic gonadal cells and TEs are activated, resulting in germline loss and a block in germline stem cell differentiation. We propose that heterochromatin protects the germline by activating the piRNA pathway. Examination of H3K9me3 marks in the wild type gonad