Fig. 3. Regulation of CrebA by Fkh. A map of the region upstream of the CrebA transcription unit showing the 2.8 kb enhancer fragment that drives reporter gene expression in the salivary gland (A). This fragment is just upstream of a P-element insertion (B204) that results in ß-gal expression in only the salivary gland and amnioserosa. Two subfragments of 1100 and 770 bp also resulted in salivary gland expression of a lacZ reporter gene, with the CrebA 770 fragment driving salivary gland expression slightly earlier than the CrebA 1100 fragment (B,C). The CrebA 770 fragment has four Fkh consensus binding sites (A, blue circles) as well as two consensus Scr/Exd/Hth-binding sites (A, blue circles with black edges). The Creb 1100 site has six Fkh consensus binding sites and no consensus Scr/Exd/Hth-binding sites (A). The CrebA 1100 lacZ construct is not expressed to high levels in the salivary glands of fkh mutant embryos (D), with only some very low level expression detectable at late embryonic stages (D, right-most embryo, arrows). CrebA 1100 constructs with all six Fkh consensus sites mutated also show a loss of reporter gene expression specifically in the salivary gland (E), again with only some very low level expression detectable in late embryonic stages (E, right-most embryo, arrows).