Fig. 5. Ago is dispensable for mitosis but is required for endocycles in follicle cell epithelium. (A) The ago mRNA is expressed in both mitotic and endocycling follicle cells (arrows). (B) Ago is responsible for CycE degradation; follicle cells in ago (hsFlp;; ago FRT80B/Ubi-GFP FRT80B) clones show increased level of CycE protein at all stages during oogenesis. Ago loss-of-function does not affect the mitotic cycles in follicle cells: ago clones showed normal expression pattern of stg (C; expression prior to st. 6, red arrow, but not past st. 6, black arrow) and the ratio between the number of cells in sister versus mutant clone was 1:0.9 (D). However, ago clones halt the transition to endocycles: prolonged CycB expression (E,E'), small nuclei size (F,F'; clones marked with elevation of CycE levels) and highly reduced BrdU incorporation during both endocycles (G,G') and amplification (H,H') are observed in ago clones. Green, GFP (B,C,E), BrdU (G,H); red, CycE (B, CycE level marks the clones in F-H), ß-gal (C), CycB (E); blue, DAPI.