The Mi{MIC} transposon carries an attP-flanked cassette containing the yellow gene. This cassette can be replaced by Recombinase-Mediated Cassette Exchange catalyzed by phiC31 integrase.
The paper Diao et al. (2015) "Plug-and-play genetic access to Drosophila cell types using exchangeable exon cassettes" describes donor constructs with attB-flanked cassettes encoding a variety of effector proteins including GAL4, GAL80 and QF. As shown in the following figure, these proteins can be expressed in the pattern of a gene when cassettes are swapped into an intronic Mi{MIC} insertion.
The self-cleaving T2A peptide assures that the effectors are not expressed as fusion proteins.
Diao et al. (2015) called these swappable cassettes "Trojan exons" by analogy to the Trojan Horse. The cassettes can be introduced by injecting embryos with plasmids, but a more convenient method involves excising them from donor constructs with cre recombinase. The P{lox(Trojan-GAL4)x3} construct illustrated below can donate GAL4-encoding Trojan exons in all three reading frames. Donor constructs for single reading frames are also available.
See "Donor stocks" for lines carrying insertions of these constructs:
| Construct | Effector | Coding phase | Construct symbol in Diao et al. (2015) |
| P{loxP(Trojan-GAL4.0)} | GAL4 | 0 | pC-(loxP2-attB2-SA(0)-T2A-Gal4-Hsp70) |
| P{loxP(Trojan-GAL4.1)} | GAL4 | 1 | pC-(loxP2-attB2-SA(1)-T2A-Gal4-Hsp70) |
| P{loxP(Trojan-GAL4.2)} | GAL4 | 2 | pC-(loxP2-attB2-SA(2)-T2A-Gal4-Hsp70) |
| P{lox(Trojan-GAL4)x3} | GAL4 | 0, 1 & 2 | pC-(lox2-attB2-SA-T2A-Gal4-Hsp70) |