UASt regulatory sequences drive expression of a mutated form of ci in which phosphorylation clusters 2 and 3 have each been mutated to a DSGXX motif (present in arm) followed by an engineered PKA site C-terminal to it, and the PKA site in phosphorylation cluster 1 has been mutated to prevent its phosphorylation (amino acid replacement S838A). The coding sequence is tagged at the N-terminal end with two copies of Tag:HA.