Fig. 8. Polarized activity of PVF1/PVR is specific to the wing imaginal disc. The polarizing activity of PVF1/PVR was followed in other epithelial tissues in which PVR is normally expressed. (A,B) In the eye imaginal disc, induction of Pvf1 by GMR-Gal4 leads to a uniform apicobasal distribution of PVF1, without any apparent defects. (C) Uniform ectodermal expression of Pvr in the embryo (by 69B-Gal4) did not disrupt the polarity of the ectoderm and the secreted cuticle. Arrow shows the position of a hole induced in the dorsal head region. (D,E) Uniform expression of Pvr in the eye disc did not disturb the organization of the epithelium and the distribution of actin. Taken together, these results demonstrate that the apical retention of PVF1, as well as the responses to PVR, are specific to the wing imaginal disc.