Figure 3.

 FGF and activin activate expression of a reporter gene construct containing 2.1 kb of Xbra2 5′-flanking sequence. Sequences upstream of −381 in the Xbra2 5′-flanking sequence are dispensable for response of Xbra2 to FGF (25 ng/ml) and activin. Embryos were injected with the indicated constructs and reference plasmid and, in some cases, with 1 pg of activin mRNA, as described in Materials and Methods. Normalized firefly luciferase activity from stage 12.5 caps is expressed as fold activation over untreated caps. (n) Number of experiments.