Fig. 6. Overexpression of cv-c produces long actin-filled cellular extensions. (A,B) Wild-type (A) and cv-c^M62 (B) stage 16 embryos stained with anti-Cut (light brown) to label the MpT nuclei and 22C10 (dark brown) to label the tip cell. The tip cell is present and has a normal morphology in cv-c^M62 homozygotes. (C,D) The tip cell stalk of a wild-type embryo is 7 µm (C) but increases dramatically in length in embryos in which UAS-cv-c has been expressed in the tubule using CtB-Gal4; in many cases, the length of the stalk exceeds 50 µm (D) (n=56). (E,F) Stage 16 embryos expressing UAS-GMA in the MpTs to label F-actin (green), either in the absence of cv-c overexpression (E) or when cv-c is overexpressed (F); the extended tip cell stalk is associated with F-actin. (G) CtB-Gal4>UAS-GMA;UAS-cv-c embryo co-stained for GFP (green) and the apical membrane marker Sas (red, overlap in yellow). The tip cell stalk does not stain for Sas, indicating that the extension is of basolateral membrane. (H) 22C10 staining of a stage 16 embryo in which a dominant-negative Rho1 construct (UAS-RhoN19) has been overexpressed in the tubules; the tip cell stalk is extended (n=22). In all figures, arrowheads indicate the extent of the tip cell. Scale bars: 10 µm.