Autophagy is activated in dying nurse cells during late oogenesis in D. melanogaster. (A–C) Confocal micrographs of egg chambers of flies expressing the UASp-GFP-mCherry-DrAtg8a transgene exclusively in the germline (genotype: UASp-GFP-mCherry-DrAtg8a/+; nanos-VP-16 Gal4/+). Expression of UASp-GFP-mCherry-DrAtg8a exhibits punctate staining pattern (arrows). Note that during developmental stages early 12 (A) and late 12 (B), the punctate dots are yellow (merge). In late stage 13 (C), large red dots are evident, indicating the presence of acidic compartments (autolysosomes; arrows). The arrowheads in A point to the physical connection between the oocyte and the nurse cells during early stage 12 (not observed during late stage 12). (D and E) Transmission electron micrographs of nurse cells in stage 12 (D) and in stage 13 (E) egg chambers. Autophagosomes (inset in D) and autolysosomes (arrow in E) are evident in the remaining nurse cell cytoplasm (arrow in D indicates actin bundles). Note that the autolysosome shown in E contains condensed material resembling the material of the condensed and fragmented nurse cell nucleus (NCN), providing evidence for nuclear autophagy. (F) Nurse cell of a late stage 13 egg chamber expressing UASp-mCherry-DrAtg8a exclusively in the germline (genotype: UASp-mCherry-DrAtg8a/+; nanos-VP-16 Gal4/+). mCherry-DrAtg8a puncta are attached to or located adjacent to the fragmented nucleus (arrows and insets). Hoechst staining (blue) was performed to visualize the nuclei. Nurse cells are outlined with a white line. FC, follicle cell; FCN, follicle cell nucleus; OC, oocyte. Bars: (A–C) 10 µm; (D–F) 1 µm.