Profoundly different sexual behaviour and physiology in the fruit fly depends on the action of one gene.

The fruit fly Drosophila shows distinctive courtship behaviour. The male vibrates his wings to create a courtship 'song' and chases the female, who tends to spurn his advances and run away. The male touches and licks her; eventually, if all goes well, she allows him to copulate with her.

These stereotyped behaviours are dependent on proteins encoded by the fruitless (fru) gene, which comes in male-specific and female-specific forms. In fact, males produce three different proteins (isoforms), which vary in their DNA-binding abilities. Stephen Goodwin and colleagues recently isolated and analysed a mutation that removes one male-specific form.

Male flies lacking this isoform showed less courtship behaviour and were infertile. On its own, this isoform controls differentiation of a male-specific muscle and its associated motor neuron. It is also needed, in combination with other male isoforms, for development of serotonin neurons involved in male copulatory behaviour.

The research highlights how a single gene, producing a range of isoforms that act individually or in combination, can have multiple effects on cells – and ultimately far-reaching effects on nervous system development and hence on a complex behaviour.

External links

• Billeter JC et al. Isoform-specific control of male neuronal differentiation and behavior in Drosophila by the fruitless gene. Curr Biol 2006;16(11):1063–76.