A mutated form of ci (with mutations in the potential PKA phosphorylation sites a, b, 1, 2, 3, A and B), tagged at the N-terminal end with amino acids MDQNNSLPPY of Tag:TBP-3G3 is expressed under the control of UASt regulatory sequences. The amino acid changes are T512A, T589A, S838A, S855A, S856A, S891A, S892A, S962A and T1006A.