The loxP cassette containing the Avic\GFPGMR.PS marker has been excised. This results in a fru locus in which the endogenous fru P1 promoter drives expression of GAL4 instead of the fru[M] isoform. A transcriptional stop signal and a single loxP site remain downstream of the GAL4 open reading frame.
Photoactivation of fru-expressing neurons in headless females expressing Rnor\P2rx2Scer\UAS.cLa under the control of Scer\GAL4fru-GAL4 in a fruM/fruGAL4 background produces courtship songs with acoustic characteristics similar to those seen in headless males expressing Rnor\P2rx2Scer\UAS.cLa under the control of Scer\GAL4fru-GAL4 in a fru[+] background. Recordings of these courtship songs substitute fully for the songs of courting males in an assay where the song is played back to fly pairs consisting of a wingless male (which cannot produce a courtship song) and a virgin female).