Abstract: The Drosophila melanogaster accessory gland is a functional analog of the mammalian prostate. This tissue is responsible for making and secreting seminal fluid proteins and other molecules that are critical for successful reproduction. It has been shown that this tissue grows with age and the main, binucleated, epithelial cell type contributes to this growth by undergoing a variant cell cycle termed an endocycle. Preliminary data reveals that the adult accessory gland contains a novel, mitotic progenitor cell population that may also play a key role in tissue homeostasis and regeneration upon damage. This research plan will establish the tools necessary for future studies and investigate the dynamics of the accessory gland progenitor cell population with age, mating, and during regeneration from damage by: (1) using single cell RNA sequencing to establish a progenitor cell specific transcriptome and progenitor cell specific driver lines, (2) characterizing the cell cycle status and differentiation ability of these cells with age and mating, and (3) describing the function of these cells in accessory gland homeostasis and regeneration. The experiments proposed here will allow for additional technical training in single cell RNA sequencing and analytical training in lineage tracing and cell cycle regulation of a novel progenitor cell population. Due to it's structural and functional similarities to the mammalian prostate and the short lifespan of the fruit fly, the Drosophila accessory gland is an effective model for studying misregulation of prostate tissue homeostasis, fertility issues, and regeneration.