DmIKKε knock-down alters the DIAP1 degradation pattern and impairs morphogenesis of the shaft cell. (A) PRAP dynamics in the wild-type SOP lineage. Dashed lines outline the nuclei. Bar, 5 µm. (B) External adult bristles in a wild-type fly. Bar, 10 µm. The tip of a bristle is indicated by a white arrow. (C) In the DmIKKε knock-down SOP lineage, PRAP degradation is delayed, and PRAP is still detectable after bristle elongation starts. (D) Microchaetes of the DmIKKε knock-down flies are shorter and thicker than the wild-type bristles shown in B. (E) Bristle length (mean ± SD) is significantly shorter in lineages with delayed PRAP degradation (53.4 ± 4.76 µm; n = 7) than in lineages showing the normal PRAP pattern (65.4 ± 3.46 µm; n = 34). The P value was calculated using an unpaired two-tailed Student's t test. ***, P < 0.0001. (F) Genetic interaction between diap1 and DmIKKε in shaft cell formation. DmIKKε was reduced by DmIKKε^dsRNA. DIAP1 level was enhanced by the overexpression of myc-tagged DIAP1. (G) Effects of DmIKKε, Dronc, and drICE/DCP-1 on shaft-cell formation. The average bristle lengths in individual flies are plotted (n = 10 flies). Asterisks indicate statistical significance compared with control, as determined by one-way ANOVA with Tukey's HSD post-hoc analysis. *, P < 0.05; ***, P < 0.001; n.s., not significant. Data are shown as the mean ± SEM. (H) Dronc was activated in the shaft cell during bristle elongation. The processed form of Dronc was detected using an antibody specific for activated Dronc. The socket cell (section 1) and shaft cell (section 2) are shown. Arrowheads indicate the positions of the socket or shaft cells in each section. Bar, 10 µm. Genotypes: sca-GAL4 UAS-PRAP/+; UAS-Histone2B-ECFP/+ (A), sca-GAL4 UAS-PRAP/+; UAS-Histone2B-ECFP/UAS-IR2615 (C and E), and sca-GAL4/UAS-GFP (H).