Piwi maintains homeostasis and silences transposons in the Drosophila adult intestine

Piwi genes are well known for their germline functions, such as transposon silencing, stem cell self-renewal, and subsequent steps of gametogenesis. However, little is known about their role in somatic tissues. Here, we report the function of Drosophila piwi gene in the adult gut, in which intestinal stem cells (ISCs) produce enteroendocrine cells and enteroblasts that generate enterocytes. We show that piwi is expressed in ISCs and enteroblasts. Piwi deficiency reduced ISC number, compromised enteroblast maintenance, and induced apoptosis mostly in enterocytes, but did not affect ISC proliferation and their differentiation to enteroendocrine cells. In addition, deficiency of zygotic but not maternal piwi de-silenced many retrotransposons in the adult gut. Importantly, either piwi mutations or piwi knock-down specifically in ISCs and enteroblasts shortened the organism lifespan, indicating that the intestinal function of piwi has a major effect on Drosophila viability and longevity. Finally, genes differentially expressed in the piwi mutant gut are largely involved in metabolism, oxidation, and reduction, implying that Piwi achieve its intestinal function by regulating diverse molecular processes