Ables, Elizabeth TweediePhipps, Daniel Noah2023-02-072024-07-012022-072022-07-01July 2022http://hdl.handle.net/10342/12197Oogenesis, the process by which a viable egg is produced, demands carefully coordinated communication between somatic and germ cell populations, relying on both local and systemic factors such as steroid hormones for signaling. In Drosophila, the steroid hormone ecdysone is crucial for a variety of physiological processes throughout development and adulthood, including oogenesis. Ecdysone signaling largely relies on the nuclear receptor Ecdysone Receptor (EcR) to receive the hormone as a ligand, resulting in transcriptional activation and regulation of downstream targets. The relative contribution of EcR in germ cells versus somatic cells for proper oogenesis, however, is unknown. Previous analyses of EcR function in oogenesis relied on manipulation of somatic cell types or global mutations, leaving the role for EcR in the germline rather speculative. A lack of germline-compatible tools to study EcR has been a key contributor to this knowledge gap. To address this, we generated three germline-enhanced UAS-RNAi lines against EcR that effectively reduce EcR mRNA levels in germ cells. Consistent with the phenotype of EcR global mutants, depletion of EcR in germline mosaics and ubiquitously in all germ cells depletes the number of germline stem cells over time. Intriguingly, we also find that knockdown of EcR in germ cells results in phenotypes not previously linked to ecdysone signaling. We demonstrate that depletion of EcR in germ cells disrupts encapsulation of 16-cell cysts as they move posteriorly to form egg chambers. This suggests that EcR is required specifically in germ cells for them to actively contribute to their own encapsulation and posits that EcR may have unique transcriptional targets in germ cells at this stage of oogenesis. These tools will be highly useful in future studies to understand how ecdysone signaling impacts the relationship between the germline and soma during oogenesis.application/pdfenoogenesisecdysoneDrosophilaMaster's Thesis2023-01-31