Transgenic construct used to study the MCP silencer from the Abd-B gene. Contains the Ubx PBX enhancer, a SalI-XbaI fragment containing the MCP silencer (all 5 pho protein-binding sites in this fragment has been mutated), and a lacZ reporter that is driven by the proximal Ubx promoter. The MCP fragment is flanked by FRT sites, allowing it to be excised using FLP recombinase.