Figure 5.

Depletion of hd during canonical mitotic cell cycles results in a G2/M arrest. (A) An ovariole from a control hsp70-FLPase; FRT hd^Ff/FRT hd⁺ GFP⁺ female that was not heat induced. Labeling of this ovariole with anti-GFP (green) and anti-cyclin B (red) reveals oscillating levels of Cyclin B in follicle cells during mitotic division cycles up until stage 6 (S6), but not in endocycling follicle cells of stage 7 (S7) and later egg chambers. The large polyploid nurse cells in the interior of the egg chamber that switch into endocycles before stage 1 do not express mitotic cyclins during these stages. Inset: A higher magnification of a follicle cell with Cyclin B in cytoplasm and nucleus. (B) An ovariole from an hsp70-FLPase; FRT hd^Ff/FRT hd⁺ GFP⁺ female, in which an hd^Ff/hd^Ff null mutant clone (arrow, GFP⁻) was heat induced 2 days earlier. After initial cell divisions, slow depletion of Hd protein in the hd^Ff null cells results in their arrest with high levels of Cyclin B in the cytoplasm but not nucleus, suggestive of a G2/M arrest, which persists after stage 6. Inset: A higher magnification of a hd mutant follicle cell arrested with Cyclin B in the cytoplasm but not nucleus. Bar, 25 μm for main panels, 6 μm for insets.