For fruit flies, siestas are gene-driven

A siesta-suppressing gene helps fruit flies (Drosophila) nap when they need to but not sleep their lives away, new research suggests.

That’s no small thing.

In fact, it probably helped them expand beyond their ancestral home in equatorial Africa to successfully colonise temperate zones around the world, says Isaac Edery, from Rutgers University in the US, who led the study.

And it may shed light on the biology that helps many creatures, including humans, balance the benefits of 40 winks against those of getting important activities done during the day.

Edery and colleagues have dubbed it the “daywake” gene.

When temperatures are cool, they say, it activates to suppress the tendency for Drosophila to take a daytime nap – presumably so they can spend more time seeking food or mates. 

“This gene contributes to behavioural flexibility, or the ability to hide from the noontime sun when weather is hot but engage in activities good for survival when the weather is cool,” says Edery. 

Daywake sits adjacent to and slightly overlaps a previously documented gene, called “period,” that regulates the flies’ circadian clock and governs daily wake-sleep cycles. 

The researchers found that daywake activity is increased by a specific sequence within the period gene, and that this process happens most efficiently when the flies are exposed to cold temperatures. Night sleep is not affected.

“Although the daywake gene is not present in humans, our finding reinforces the idea that night-time sleep and daytime siesta are governed by distinct mechanisms and serve separate functions for health and survival,” Edery says.

The study is published in the journal Current Biology.