Fig. 7. Mutational analysis of the putative T-box binding sites in the derrière promoter. (A) Diagrams showing the constructs used and the mutations made in the T-box binding sites. (B) Luciferase assay in animal caps showing that induction of the firefly luciferase reporter gene is independent of the T-box sites. (C-F) Vegetal views of stage 10.5 transgenic Xenopus embryos expressing the indicated transgenes. Note that all four constructs are expressed in the mesendoderm. Expression of the Tbs1,2 construct in the case illustrated in F is higher in the endoderm than the mesoderm, but this is not a consistent observation.