Ferri, S.L., Bohm, R.A., Lincicome, H.E., Hall, J.C., Villella, A. (2008). fruitless Gene products truncated of their male-like qualities promote neural and behavioral maleness in Drosophila if these proteins are produced in the right places at the right times.  J. Neurogenet. 22(1): 17--55.

FBrf0216018

Research paper

To bring GAL4 production under the control of the sex promoter (P1) contained within Drosophila's fruitless gene, a gal4 cassette was previously inserted downstream of P1. This insert should eliminate male-specific FRU(M) proteins, which normally contain 101 amino acids (aa's) at their N termini. Thus males homozygous for the P1-gal4 insert should be courtless, as was briefly stated to be so in the initial report of this transgenic type. But XY flies whose only fru form is P1-gal4 have now been found to court vigorously. P1-gal4 females displayed no appreciable male-like actions except courtship rejection behaviors; yet, they developed a male-specific abdominal muscle. No immunoreactivity against the male-specific aa's was detectable in P1-gal4 flies. But male-like neural signals were observed in XY or XX P1-gal4 pupae and adults after applying an antibody that detects all FRU isoforms; transgenic females displayed reduced expression of such proteins. RT-PCR's rationalized these findings: P1 transcripts include anomalous splice forms from which gal4 was removed, allowing FRU's lacking M aa's to be produced in male-like patterns in both sexes. Within males, such defective proteins promote neural differentiation and function that is sufficient to support spirited P1-gal4 courtship. But dispensability of the male-specific FRU N-terminus is tempered by the finding that intra-fru sequences encoding these 101 aa's are highly conserved among interspecific relatives of D. melanogaster.