Recombination between the FRT sites present in each of the PBac{Ubi-p63E.FRT} and PBac{FRT.GFP} constructs reconstitutes a functional "Ubi-GFP" transgene (PBac{Ubi-p63E.FRT.GFP}), with expression of EGFP driven by the Ubi-p63E promoter.