Fig. 1. Effect of paired-Gal4-driven En on the expression of negative and positive targets. In this and all subsequent figures the domain of paired-Gal4 expression is marked by a blue rectangle. Embryos are all at st11 and the identity of segments is indicated (T, thoracic; A, Abdominal). Whole embryos are shown lying on their side, whereas higher magnifications show ventral views with the ventral midline running in the middle from left to right. (A,B) Expression of ci in a wild-type embryo (A) and in an embryo expressing ectopic En under the control of paired-Gal4 (prd-G4 UAS-en) (B). In addition to repression in the normal domain of En expression, ectopic repression of ci expression is seen in alternate segments, within the paired domain. (C,D) Expression of hh in a wild-type (C) and paired-Gal4 UAS-en (D) embryo. Here, ectopic expansion of hh expression is seen in the paired-domain (D). (E,F) Expression of endogenous en in a wild-type (E) and paired-Gal4 UAS-en (F) embryo. A probe from the 3' UTR that is not present in the UAS-en construct was used to detect endogenous expression. Endogenous en expression is activated by ectopic En. Note that repression and activation occur both in the thorax and abdomen.