Fig. 7. Kette regulates F-actin formation in vivo. (A-D) Top row, dorsal view of a Drosophila notum. Bottom row, higher magnification showing the morphology of microchaete and epidermal hairs (scale bar: 10 µm). (A) Wild-type flies are characterized by an ordered array of macro- and microchaete, which are normally thin, straight and with a pointed end (E). All epidermal cells generate a small hair. (B) After expression of three copies of a UAS-Kette^Myr transgene in the scabrous pattern, bristle morphology is severely disrupted. Kette^Myr expression results in shorter, branched and thicker bristles (G). In addition, epidermal cells generate more than one hair (arrow). The area boxed in red is shown enlarged. (C) After expression of two copies the UAS-Kette^Myr transgene in the scabrous pattern results in a weaker phenotype; however, bristles are still forked and shorter (star and F) and epidermal cells develop more than one hair (arrow). The area boxed in black is shown enlarged. (D) Same genetic background as in C but lacking one copy of the wasp gene. The bristle phenotype evoked by Kette^Myr expression is suppressed. (H) During pupal development, bristle morphology is prefigured by an apical F-actin extension. (I) After Kette^Myr expression (three copies), F-actin formation is initiated in a broad region of the apical cell surface. In addition, the F-actin at the cell boundary appears to have a fuzzier organization after Kette^Myr expression. Scale bars: 100 µm in A-D; 2 µm in E-G; 10 µm in H,I.