UASp regulatory sequences drive expression of wild-type trk that is tagged at the N-terminal end with TagRFP (the tag is located between residues D34-Y35, after the N-terminal signal peptide, and is flanked with a short SAGSAS linker peptide) and at the C-terminal end with EGFP. The presence of the C-terminal EGFP tag results in loss of function of the protein.