Figure 4. Ubx enhnacer trap silencing in response to increasing Ubx+ dose.

(A) Ubx-Gal4^lac1 is silenced in groups of cells by 4 copies of the Ubx+ locus (arrows), but Ubx protein levels are normal. (B) Ubx-Gal4^lac1 is silenced in groups of cells by 3 copies of the Ubx+ locus (arrows), but Ubx protein levels are normal. (C) Wild type haltere expression pattern of Ubx-Gal4^LDN. (D) Ubx-Gal4^LDN is partially silenced by 4 copies of the Ubx+ locus. (E–G) Wild type haltere expression patterns of Ubx-lacZ^lac1 (E), Ubx-Gal4^M1 (F), and Ubx-Gal4^M3 (G). (H–J) Ubx-lacZ^lac1 (H) and Ubx-Gal4^M1 (I), but not Ubx-Gal4^M3 (J), are partially silenced by 4 copies of Ubx+. Note that for Ubx-lacZ^lac1 and Ubx-Gal4^M1, silencing does not occur in random clones, but instead is manifest by a loss of expression in proximal regions of the disc (arrows).