TI{attP(siTrojan-GAL4.2)} contains a 'split intein trojan' (siTrojan) exon in intron phase 2, composed of a splice acceptor site, the CfaN split intein preceeded by an EY sequence, a T2A peptide, the GAL4 coding sequence, a second T2A peptide, the CfaC split intein followed by a CFN sequence, a splice donor site, and an FRT cassette that contains a Disc\RFP^3xP3.cUa marker. Integration of TI{attP(siTrojan-GAL4.2)} 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 that is incorporated into the mRNA of the native Drosophila gene. The presence of the two T2A peptides is designed to ensure not only the independent translation of the GAL4 driver but also the separate translation of two fragments of the native Drosophila gene into which the cassette has inserted: an N-terminal fragment tagged (at the C-terminal end) with the EY-CfaN split intein sequence (and T2A) and a C-terminal fragment tagged (at the N-terminal end) with the CfaC-CFN split intein sequence. Trans-splicing mediated by CfaN and CfaC ligates the two protein fragments of the native Drosophila gene into a complete protein, mitigating the mutagenic effects of the siTrojan exon (although the reconstituted protein will contain a 7 amino acid insertion at the site of interruption by the coding intron). In addition, the entire siTrojan exon is flanked by a pair of inverted attP sites, which allows for the replacement of this entire sequence with DNA from a compatible donor plasmid (where the sequence to be inserted is flanked by inverted attB sites) through recombination-mediated cassette exchange (RMCE) driven by the phiC31:int integrase.