Sexual behavior: its genetic control during development and adulthood in Drosophila melanogaster.

Courtship behavior in Drosophila melanogaster males is an innate behavior pattern. Whether or not a fly will display male courtship behavior is governed by the action of a set of regulatory genes that control all aspects of somatic sexual differentiation. The wild-type function of one of these regulatory genes, transformer-2 (tra-2), is necessary for female sexual differentiation; in the absence of tra-2+ function XX individuals differentiate as males. A temperature-sensitive tra-2 allele has been used to investigate, by means of temperature shifts, when and how male courtship behavior is specified during development. The removal of tra-2ts function in the adult (by a shift of the tra-2ts mutant flies to the restrictive temperature) can lead to the appearance of male courtship behavior in flies that otherwise would not display these behaviors. These experiments suggest that the regulatory hierarchy controlling sexual differentiation is functioning in the adult central nervous system. More importantly, these results suggest that the adult central nervous system has some functional plasticity with respect to the innate behavioral pattern of male courtship and is maintained in a particular state of differentiation by the active control of gene expression in the adult.