Fig. 4. The EBS and CRE are sufficient to drive cement gland expression in the tailbud embryo and cooperate to increase expression. (A) Multimerized 14 bp regions containing the proximal EBS (region 2) or CRE (region 3) are sufficient to drive cement gland-specific expression of GFP. When the EBS or CRE are mutated (3 bp substitution in core binding site; see Materials and Methods), their ability to drive this expression is abolished. (B) In front of a heterologous promoter (adenovirus major late promoter; MLP) the 5xEBS and 5xCRE are extremely inefficient at driving gfp expression, but when multimerized together (3EBS/2CRE) the sites cooperate to drive robust expression in the cement gland. Cement gland expression of gfp in more than 25% of embryos is indicated by +++ (18-25%), ++ (9-17%), + (2-8%), +/– (no change) and – (<2%) (see Table 2; Materials and Methods).