Sti depletion causes an increase of phosphorylated Sqh at the CF in late cytokinesis. (A) Drosophila S2 cells stably expressing Sqh::GFP were treated with dsRNAs directed against kanamycin (control) or sti for 72 h and then fixed and stained to detect Sqh::GFP, tubulin, and DNA (blue). The box plots showing the quantification of Sqh::GFP fluorescence levels at the CF in early and late cytokinesis are shown at the bottom. The intensity of Sqh::GFP fluorescence at the CF was calculated using the formula shown, in which I_CF is the fluorescence intensity at the CF, and I_C represents the background intensity measured within an identical area inside the cytoplasm. At least 30 cells from two separate experiments were analyzed. AU, arbitrary unit. (B) S2 cells were treated with dsRNAs directed against the kanamycin gene (control), sti, or rok for 72 h and then fixed and stained to detect Sqh1P, tubulin, and DNA (blue). Quantification of Sqh1P levels was performed as described in A. Note that the Sqh1P staining on centrosomes is not specific because it was not affected by ROK depletion, and Sqh::GFP never localized to centrosomes (Fig. S2 B). **, P < 0.01 (Student’s t test). (C) S2 cells were treated with dsRNAs directed against kanamycin (control), sti, or rok for 72 h and then fixed and stained to detect Sqh2P, tubulin, and DNA (blue). In each box plot, the box contains the values comprised between the 25th and 75th percentile, and the horizontal line inside the box marks the median. The ends of the whiskers indicate the minimum and maximum values. Bars, 10 µm.