Fig. 2. Ectopic Pax proteins in eye-antennal disc generate headless flies. Scanning electron micrographs of the anterior portion of ey-Gal4/+; UAS-Gsb-1/+ (A-D), homozygous eyD (E) and wild-type flies (F) are compared. The interference with head development of ectopic Gsb (D-Pax2, Poxn, Poxm, or Prd) in eye-antennal discs results in ‘headless’ flies of variable expressivity. Representative phenotypes of the four phenotypic classes are shown: (A) class I, all head structures derived from eye-antennal disc, including eye, antenna, head capsule and maxillary palps, are missing, only the proboscis, largely derived from the clypeolabral (cl) and labial disc (lbl), is present; (B) class II, most head structures and both eyes and antennae absent; (C) class III, large parts of head and both eyes missing, portions of one or both antennae (ant) present; and (D) class IV, most of head and one or both eyes of reduced size present. Note that flies homozygous for the strong eyD allele also exhibit a headless phenotype (E). ant, antenna; cl, clypeus; lbl, labellum; lr, labrum; mpl, maxillary palp.
