Fig. 1. In vivo deletion analysis identifies a 901 bp enhancer that directs PLE-specific expression of FoxE3. (A) FoxE3 expression in X. tropicalis embryos (stage 23) detected by in situ hybridization. (B-G) GFP expression detected by in situ hybridization in representative transgenic embryos (stages 22-24) generated with the reporter constructs shown to the left. White and black arrows in A-G indicate the PLE. The arrowhead in B indicates ectopic GFP expression in the presumptive oral ectoderm. Numbers of embryos with GFP expression in the PLE and the total number of normally (or near normally) developing embryos injected with each construct are indicated to the right, along with the percentage of GFP-positive cases. The 901 bp element necessary for PLE-specific expression is boxed with a dotted red line. ^*The expression in D was positive in the PLE but very spotty and broad, as shown in the left-hand panel.