Fig. 1. Identification of pygo as a new segment polarity gene required for Wg signaling. Wings are oriented proximal towards the left and anterior upwards (A-C). A wild-type wing is shown in A. A wing with somatic clones of pygo^F66 is shown in B. The enlarged parts of the wing in B are shown in C. Clones of pygo^F66 (B) cause wing notching and the formation of ectopic bristles in nearby tissues. The wing phenotypes associated with pygo^F66 are fully penetrant. Virtually identical results were obtained from other pygo alleles. The cuticle phenotypes of wild-type (D) and pygo mutant embryos (E-H) are shown. All embryos are oriented anterior towards the left and dorsal upwards. The pygo mutant embryos in E-H were derived from homozygous pygo mutant germline clones (see Materials and Methods). The wild-type embryo (D) forms a segmented larval cuticle decorated with denticles spaced by naked cuticle. pygo mutant embryos (E-H) form unsegmented cuticles that produce ‘lawn’ of denticle hairs. Homozygous mutant embryos derived from germline clones are shown for pygo^F15 (E), pygo^F66 (F) and pygo^F107(H). A pygo mutant embryo shown in G was derived from a homozygous pygo^F15 mutant germline clone and paternally mutant for pygo^F66.