Insertion of sequence into fru intron 1. The insert contains duplicated fru intron 1 sequence, GAL4 coding sequence in the same orientation as fru, transcription stop signals in both orientations and a loxP flanked Avic\GFPGMR.PS marker in reverse orientation. In the resulting fru locus, the endogenous fru P1 promoter drives expression of GAL4 instead of the fru[M] isoform.