Donald A. Gailey

Isoform-Specific Control of Male Neuronal Differentiation and Behavior in Drosophila by the fruitless Gene

BACKGROUND How the central nervous system (CNS) develops to implement innate behaviors remains largely unknown. Drosophila male sexual behavior has long been used as a model to address this question. The male-specific products of fruitless (fru) are pivotal to the emergence of this behavior. These putative transcription factors, containing one of three alternative DNA binding domains, determine the neuronal substrates for sexual behavior in male CNS. RESULTS We isolated the first fru coding mutation, resulting in complete loss of one isoform. At the neuronal level, this isoform alone controls differentiation of a male-specific muscle and its associated motorneuron. Conversely, a combination of isoforms is required for development of serotonergic neurons implicated in male copulatory behavior. Full development of these neurons requires the male-specific product of doublesex, a gene previously thought to act independently of fru. At the behavioral level, missing one isoform leads to diminished courtship behavior and infertility. We achieved the first rescue of a distinct fru behavioral phenotype, expressing a wild-type isoform in a defined subset of its normal expression pattern. CONCLUSION This study exemplifies how complex behaviors can be controlled by a single locus through multiple isoforms regulating both developmental and physiological pathways in different neuronal substrates.

Reassessment of 79B actin gene expression in the abdomen of adult Drosophila melanogaster.

The expression pattern of the 79B actin gene in Drosophila melanogaster has been inferred previously by means of a reporter gene in which 79B actin promoter sequences drive the lacZ coding sequences. Although the 79B actin gene is expressed primarily in muscles of the thorax and first abdominal segment of the adults of both sexes, expression in the remaining abdominal segments appears limited to the male genital muscles and the male‐specific Muscle of Lawrence (MOL). This reported abdominal expression pattern has been reassessed. By varying parameters of tissue preparation and lacZ reporter gene detection, expression of the 79B actin gene has been revealed in most dorsal abdominal longitudinal fibres and genital muscles of both females and males. These new results suggest that there are differences in the level of 79B actin gene expression among the various abdominal muscles of both sexes, and that abdominal expression is not limited primarily to male sex structures.