Fig. 2.

Unipolar placement of actin-based protrusions is a local property of denticle field cells. Ventral epithelium with F-actin visualized using phalloidin (red in merge panels) and cell outlines with anti-phosphotyrosine (white in merge panels). svb/ovo-positive cells were indicated by staining with anti-GFP (green in merge panels). All embryos are approximately stage 15. (A) HS-Flp Act5c>y+>-GAL4 UAS-GFP; UAS-svb/ovo embryo showing ectopic actin protrusions in svb/ovo-positive smooth field cells. (B–E) Higher magnification of the area outlined in panel A. B, merge; C, phosphotyrosine; D, actin; and E, GFP, marking ectopic Svb/Ovo expression. Top and bottom arrows indicate ABPs located mid-face and on the anterior cell edge, respectively. Other misplaced protrusions are also apparent. Middle arrow in panel B highlights an early sensory cell. (F–I) Another HS-Flp Act5c>y+>-GAL4 UAS-GFP; UAS-svb/ovo example, shown only at high magnification with ovo-positive cells exhibiting ectopic actin protrusions. Stains are as in panels B–E series. Arrows indicate actin protrusions, where upper arrow indicates one placed correctly at a posterior cell edge, while the lower protrusion is located mid-face. (J) Ptc-GAL4; UAS-svb/ovo/UAS-GFP embryo showing numerous ectopic actin protrusions in svb/ovo-positive smooth field cells. Note that these protrusions show no preference for cell boundaries. (K–N) Higher magnification of the area outlined in panel J. Arrows indicate two actin protrusions emerging from middle of cell, stains are as in panels B–E series. Scale bar = 30 μm in low magnification images and 20 μm in high magnification images.