Abstract
CTP synthase (CTPS) forms a filamentous structure termed the cytoophidium in all three domains of life. The female reproductive system of Drosophila is an excellent model for studying the physiological function of cytoophidia. Here, we use CTPSH355A, a point mutation that destroys the cytoophidium-forming ability of CTPS, to explore the in vivo function of cytoophidia. In CTPSH355A egg chambers, we observe the ingression and increased heterogeneity of follicle cells. In addition, we find that the cytoophidium-forming ability of CTPS, rather than the protein level, is the cause of the defects observed in CTPSH355A mutants. To sum up, our data indicate that cytoophidia play an important role in maintaining the integrity of follicle epithelium.