Figure 4.

Input by the posterior group converges on minimal TREs in the tailless promoter. (A–I) In situ hybridisation for lacZ reporter expression, driven by different tll promoter constructs, in stage 4 embryos: (A–C) P1, a 5.9 kb full-length tll promoter construct; (D–F) K11, tll promoter subregion −2291 to −2770, oligomerised four-fold; (G–I) G22, tll promoter subregion −324 to −200, oligomerised four-fold. (A, D, G) In a wild-type background, all constructs drive reporter expression in a posterior cap. The P1 and G22 constructs also drive expression in the anterior. Expansion of the lacZ expression pattern is apparent for all three constructs when osk is overexpressed (4xosk; C, F, I), while lacZ expression is significantly reduced for the P1 and K11 constructs, although not for G22, in osk¹⁶⁶ homozygous flies (B, E, H).