A Single-cell transcriptomic atlas of developing adult Drosophila melanogaster ovary and oogenesis

Oogenesis is a complex developmental process that involves spatiotemporally regulated coordination between the germline and supporting, somatic cell populations. This process has been modeled extensively using the Drosophila ovary. While different ovarian cell types have been identified through traditional means, the large-scale expression profiles underlying each cell type remain unknown. Using single-cell RNA sequencing technology, we have built a transcriptomic dataset for the adult Drosophila ovary and connected tissues. Using this dataset, we identified the transcriptional trajectory of the entire follicle cell population over the course of their development from stem cells to the oogenesis-to-ovulation transition. We further identify expression patterns during essential developmental events which take place in somatic and germline cell types such as differentiation, cell-cycle switching, migration, symmetry breaking, nurse cell engulfment, egg-shell formation, and corpus luteum signaling. Extensive experimental validation of unique expression patterns in both ovarian and nearby, non-ovarian cells also led to the identification of many new cell type- and stage- specific markers. The inclusion of several nearby tissue types in this dataset also led to our identification of functional convergence in expression between distantly related cell types such as the immune-related genes which were similarly expressed in immune cells (hemocytes) and ovarian somatic cells (stretched cells) during their brief phagocytic role in nurse cell engulfment. Taken together, these findings provide new insight into the temporal regulation of genes in a cell-type specific manner during oogenesis and begin to reveal the relatedness in expression between cell and tissues types.