P{loxP(Trojan-GAL4DBD.1)} is a transgenic donor construct containing a single 'Trojan GAL4DBD' cassette, in intron phase 1. The Trojan GAL4DBD sequence consists of a splice acceptor site followed by the T2A peptide, a GAL4(DBD)::Zip- hemidriver and an Hsp70 transcription termination signal. It is flanked by attB sites nested within a pair of loxP sites. Expression of P1cre recombinase will excise and circularise the cassette, which can then be integrated into a target in the genome that contains inverted attP sites, such as the Mi{MIC} element, using phiC31:int integrase. Integration of the cassette into a coding intron (with the same phase) of a native Drosophila gene of interest will result in the cassette behaving as a 'Trojan' exon: the splice acceptor site ensures that the T2A-GAL4(DBD)::Zip- open reading frame is incorporated into the mRNA of the native Drosophila gene, while the T2A sequence truncates the native gene product and promotes the separate translation of the GAL4(DBD)::Zip- open reading frame. Thus GAL4(DBD)::Zip- should be expressed under the control of the regulatory sequences of the native Drosophila gene of interest in the resulting Trojan-MiMIC GAL4(DBD)::Zip- driver line.