The pBS-KS-attB2-SA(1)-T2A-3XGAL80-Hsp70 plasmid contains a recombination-mediated cassette exchange (RMCE) cassette that consists of two inverted attB sites which surround an intron phase 1 "Trojan 3XGAL80" cassette composed of a splice acceptor site followed by: the T2A peptide - GAL80 tagged with both Tag:FLAG and Tag:HA - a P2A peptide - GAL80 tagged with EGFP - a T2A peptide - an untagged copy of GAL80 - an Hsp70 transcription termination signal. In the presence of phiC31:int integrase, the attB cassette can undergo RMCE with a target in the genome that contains inverted attP sites, such as the Mi{MIC} element, replacing the target attP cassette with the donor attB cassette sequence. 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-GAL80-P2A-GAL80-T2A-GAL80 open reading frame is incorporated into the mRNA of the native Drosophila gene, while the T2A and P2A sequences promote the separate translation of each GAL80 open reading frame (the first T2A sequence should also result in the truncation of the native gene product). Thus GAL80 should be expressed under the control of the regulatory sequences of the native Drosophila gene of interest in the resulting fly line.