A study from the Glasgow University and Oxford says that doublesex (dsx) gene in fruit fly determines the shape and structure of the male and female body. The gene also moulds the architecture of their brain and nervous system, resulting in sex-specific behaviours.
For a long time, the courtship behaviour of the fruit fly has long been used to study the relationship between genes and behaviour- it is innate, manifesting in a series of stereotypical behaviours largely performed by the male.
And until recently, the gene 'fruitless' (fru), which is specific to the adult male fruit fly, was thought to be the key to male behaviour and the development of male specific neural circuitry of flies.
However, the researchers have shown that fru does not explain the complete repertoire of male behaviours in the fly: female flies in which the fru gene has been activated demonstrate some, but not all, of the characteristics usually associated with courtship behaviour in males.
The researchers have also shown that dsx plays an important role in shaping the neural circuitry involved in this behaviour.
"The dogma was that dsx made fruit flies look the way they did and fru made them behave the way they did. We now know that this is not true. dsx and fru act together to form the neuronal networks - the wiring - for sexual behaviour," Nature quoted Dr Stephen Goodwin from the University of Oxford, who led the research, as saying.
While fru has so far been found only in insects; dsx is found throughout the animal kingdom, where it plays a fundamental role in sex determination, and so is of particular interest to researchers.
The researchers used a transgenic tool generated in his lab and could map dsx throughout the fly's development using a fluorescent protein marker that illuminates areas where DSX is active.
This highlighted profound differences in neural architecture between the sexes.
In males, the researchers were able to show that dsx complements fru activity to create a 'shared' male-specific neural circuit; in females (where fru is inactive), dsx forms a female-specific circuit.
Importantly the researchers could to manipulate these cells, impinging their ability to function, and show that these circuits are responsible for behaviours unique to the individual sexes.
"It has been suggested that there are only minor trivial differences between the neural circuits that underlie behaviour in males and females. We have shown that in fact there is quite a bit of difference in the number of neurons and how these neurons connect, or 'talk', to each other. These differences can have big consequences on the structure and function of the nervous system," explained Goodwin.
In addition, while dsx was known to establish the gender of the adult fly, the pattern of dsx activity in the adult was unknown.
The researchers have shown that this pattern is not ubiquitous, but rather is restricted in a specific and telling manner.
The study has been published in the journal Nature Neuroscience.