The dual functions of a sex determination gene in Drosophila melanogaster

The wild-type function of the sex transforming gene transformer-2 (tra-2) is shown to be required for normal spermatogenesis in XY males. A temperature-shift experiment using the tra-2^ts2 allele suggests that tra-2⁺ must function during the middle stages of spermatogenesis to ensure development of functional sperm. Our results, taken together with those of T. Schüpbach (1982, Dev. Biol.89, 117-127) indicate that the tra-2⁺ gene functions in the male germ line and thus, in contrast to all other sex determination loci examined to date (doublesex, intersex, transformer), its action is not limited to the soma. Orcein-stained testis preparations from tra-2 males reveal a spermiogenic defect similar to that associated with dominant male sterile (X; autosome) translocations.