GATA factor Serpent promotes phagocytosis in non-professional phagocytes during Drosophila oogenesis

Clearance of dying cells is essential for tissue homeostasis and requires both professional and non-professional phagocytes; however, it is unclear what promotes phagocytosis by non-professional phagocytes. Follicle cells of Drosophila egg chambers function as non-professional phagocytes to clear large germ cell debris in mid and late oogenesis, providing an excellent model for the study of non-professional phagocytes. Here, we demonstrate that GATA factor Serpent (Srp) plays an indispensable role in promoting the phagocytic capacity of follicle cells in both processes. Srp is upregulated in follicle cells of degenerating mid-stage egg chambers, and its knockdown results in incomplete clearance of germ cell debris and premature follicle cell death. In addition, Srp is upregulated in stretch follicle cells and is essential for clearing the nurse cell nuclei in late oogenesis. Genetic analysis reveals that Srp acts downstream of JNK signaling to upregulate the expression of the phagocytic receptor Draper as well as other components in the corpse processing machinery. Our findings highlight the crucial role for Srp in non-professional phagocytes during Drosophila oogenesis, which may also be conserved across species.