UASp regulatory sequences drive expression of a dominant-negative form of cact in which Ser residues 74, 78 and 116 have been mutated to Ala, rendering the protein insensitive to Tl receptor dependent phosphorylation, and subsequent ubiquitination and degradation. The cact sequence is tagged at the C-terminal end with 3 copies of the Tag:MYC epitope and a light-inducible degron sequence (Tag:degron(psd)). However, for this construct, there is little difference in the phenotype seen in the dark or after blue-light illumination.