Fig. 8. A repressive heterodimer partner can down-regulate GAL4-LBD activation. (A) GAL4-DHR3 is active in many tissues of a late third instar larva, including the epidermis, midgut, central nervous system (CNS) and fat body. (B) Ectopic expression of E75B results in a significantly reduced level of activation at this stage in development, recapitulating the pattern normally seen in early prepupae (C), in the presence of endogenous E75B expression. E75B-mediated downregulation of GAL4-DHR3 activity in the midgut is restricted to the proventriculus (compare arrows).