Mi{siTrojan-GAL4.1} represents a transgenic construct generated in vivo by using phiC31:int-mediated recombination to replace the attP cassette of a Mi{MIC} element insertion with an intron phase 1 'split intein trojan' (siTrojan) exon that encodes GAL4. The siTrojan exon is 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, and a splice donor site. Integration of Mi{siTrojan-GAL4.1} 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).