Median bundle neurons coordinate behaviours during Drosophila male courtship

Throughout the animal kingdom the innate nature of basic behaviour routines suggests that the underlying neuronal substrates necessary for their execution are genetically determined and developmentally programmed(1-2). Complex innate behaviours require proper timing and ordering of individual component behaviours. In Drosophila melanogaster, analyses of combinations of mutations of the fruitless (fru) gene have shown that male-specific isoforms (Fru(M)) of the Fru transcription factor are necessary for proper execution of all steps of the innate courtship ritual(3-9). Here, we eliminate Fru(M) expression in one group of about 60 neurons in the Drosophila central nervous system and observe severely contracted courtship behaviour, including rapid courtship initiation, absence of orienting and tapping, and the simultaneous occurrence of wing vibration, licking and attempted copulation. Our results identify a small group of median bundle neurons, that in wild-type Drosophila appropriately trigger the sequential execution of the component behaviours that constitute the Drosophila courtship ritual.