UASt regulatory sequences drive expression of a mutated form of smo in which a number of phosphorylation sites in the cytoplasmic tail have been changed to Glu to mimic constitutive phosphorylation (carries the amino acid replacements S658E, S659E, S660E, S680E, S683E, S687E, S690E, S693E, S740E, S741E, T742E, S743E, S746E). The coding region is tagged with GFP.