Fig. 3. Dynamic changes in the spatial and temporal patterns of ERR LBD activation. GAL4-ERR activation patterns are shown during embryogenesis (A) and third instar larval and prepupal stages (B). (A) ERR activation switches from myoblasts (6-11 hours AEL) and muscle (10-15 hours AEL) to predominantly CNS cells (14-17 hours AEL) in the late embryo. (B) In larvae, transient and widespread activation of GAL4-ERR occurs in the mid-third instar (mid-L3) in the muscle, CNS, midgut and fat body. Background bacterial ß-galactosidase expression is seen in the larval midgut lumen of early third instar larvae (early L3). Background ß-galactosidase expression is also present in the optic lobes of the CNS from larvae and early prepupae.