GAL4 enhancer trap targeting of the Drosophila sex determination gene fruitless

Summary: The fru 4 allele of the sex determination gene fruitless is induced by insertion of a P[lacZ,ry + ] enhancer trap element. This insert also acts to disrupt expression of the fru P1 promoter derived male-specific proteins, consequently impairing male courtship behavior. fru 4 maps less than 2 kb upstream of the fru P3 promoter, whose function is essential for viability. We replaced this insert with a GAL4 element, P[GAL4,w + ], recovering two lines with insertions in opposite orientations at the locus, one of which demonstrated fru-specific mutant phenotypes. Reporter expression of these lines recapitulated that of P3- and P4-derived proteins which, when correlated with a developmental and tissue specific survey of fru promoters’ activities, uncovered a previously unsuspected complexity of fru regulation. These novel fru alleles provide the tools for manipulation of fru-expressing cells, allowing the consequent effects to be related back to specific fru functions and the regulatory units controlling these activities. genesis 42:236–246, 2005. V C 2005 Wiley-Liss, Inc.