Fig. 4. The Ubx-Gal4^SS.2 line is permanently repressed by high Ubx levels. (A-C) Transformations of haltere to wing (A), metanotum into mesonotum (B) and third leg into second one (C) in Ubx-Gal4^SS.2 UAS-Ubx flies. The arrow in B marks mesonotum tissue appearing in the metanotum, and the arrow in C indicates an ectopic apical bristle on the third leg (III). The arrowhead indicates the wild-type apical bristle on the second leg (II). (D) Haltere disc of a Ubx-Gal4^SS.2/UAS-GFP larva, showing GFP expression (in green) in the anterior compartment. The posterior compartment is marked by En expression (in red). (E-G) Haltere disc of an UAS-GFP/+; Ubx-Gal4^SS.2/UAS-Ubx larva showing the same GFP (E, in green) and Ubx (F, in red) expression in patches of cells, indicating that the endogenous Ubx and the Gal4 driver are coincidentally repressed (G, merged image). (H) Map of the Ubx region showing the position of the Ubx-Gal4^M1, Ubx-Gal4^M3 (de Navas et al., 2006) and Ubx-Gal4^SS.2 insertions. The latter is close to the PRE. Discs are oriented with the anterior compartment towards the left and the ventral compartment upwards.