Fig. 5. The Pc group of genes are required for the permanent Ubx repression. (A) Histogram showing the percentage of halteres that are transformed into wings in UbxGal4^SS.2 UAS-Ubx animals in different mutant backgrounds. U stands for UbxGal4^SS.2 UAS-Ubx. In each pair of columns, we show the control (TM6B; left) and the experimental (right) percentages, indicated over each column. The number of halteres scored is indicated below each column. The heterozygosity for Pc³ decreases the percentage (and the expressivity) of the transformations, whereas the heterozygosity for trx increases the number of transformations. (B) Histogram showing the average percentage of the area in the dorsal compartment of the haltere disc in which Ubx expression is absent. The red and blue columns correspond to average percentages in ap-Gal4 UAS-GFP/+; UAS-Ubx tub-Gal80^ts/TM6B and ap-Gal4 UAS-GFP/+; UAS-Ubx tub-Gal80^ts/UAS-PclRNAi haltere discs, respectively. The data are from larvae that completed embryonic development at 17°C, were incubated for 2 (left) and 3 (right) days at 29°C, and were then transferred to 17°C. Numbers of halteres studied are above the columns. Representative examples of Ubx staining in the haltere discs of the corresponding days and genotypes are shown below. (C-C'') Haltere disc of a sd-Gal4/hs-flp; UAS-Ubx/tub-Gal80^ts; Ubi-GFP FRT2A/hs-CD2 ri Pc^XT109 FRT2A larva that went through temperature changes to establish Ubx permanent repression (see Materials and methods) and in which several Pc mutant clones (marked by the absence of GFP, in green in C) were induced. There is derepression of Ubx in the clones (in red, C'), showing that Pc is required to maintain permanent repression. The weak derepression in some clones may be related to the position of the clone. There are also cells in which Ubx has not been repressed (asterisk). Merged image in C''. Discs are oriented with the anterior compartment towards the left and the ventral compartment upwards.