TI{T-LEM.2.RFP-} consists of a recombination-mediated cassette exchange (RMCE) cassette flanked by a pair of inverted attP sites. Inside the attP sites is a T2A-LexA expression module (T-LEM) in intron phase 2 (composed of a splice acceptor site followed by the T2A peptide, the lexA::QF coding sequence and an Hsp70 transcription termination signal), followed by a single loxP site. TI{T-LEM.2.RFP-} is generated in vivo from TI{T-LEM.2} by P1cre recombinase-mediated excision of a loxP cassette containing the Disc\RFP^3xP3.PB marker (leaving the single loxP site as the remnant of this excision). If the TI{T-LEM.2.RFP-} cassette is inserted in a coding intron (with the same phase) of a native Drosophila gene of interest, this can result in the T-LEM module behaving as a 'Trojan' exon: the splice acceptor site ensures that the T2A-lexA::QF 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 lexA::QF open reading frame. Thus lexA::QF should be expressed under the control of the regulatory sequences of the native Drosophila gene of interest in the resulting fly line.