Single circadian clock regulates flies' response to light and temperature

May 8, 2007

Animals have biological clocks with a cycle of about 24 hours — these circadian rhythms allow them to align their physiology and behavior to the earth’s rotation. Now new research from Rockefeller University shows that the same molecular clock responsible for helping flies sync themselves with patterns of light and dark might be what helps them sync to patterns of temperature, too.

Researchers in the lab of Michael Young, the Richard and Jeanne Fisher Professor and head of the Laboratory of Genetics, took adult Drosophila and placed them in a dark environment where the only variable was temperature, which alternated between warm and cool in 12-hour intervals. After a few days of temperature variability, the scientists then held the temperature steady in the warm phase, at about 77 degrees Fahrenheit, to see whether their molecular clocks continued to cycle in the absence of temperature fluctuations.

When they looked at gene activity in the flies’ heads, where their light-sensing capabilities are located, the researchers found a great deal of overlap between those genes that oscillate in response to cycles of light and dark, and those that oscillate according to cycles of temperature. Upon closer examination, they saw that although temperature-regulated genes also appear to be activated by light, as indicated by measurements of the transcripts the genes produce, the opposite was not true: Not all light-regulated genes fluctuate with temperature. “So, it seems that the temperature transcripts are a subset of the light transcripts,” says Catharine Boothroyd, a postdoc in the lab and the paper's first author. This, she says, means that the temperature-responsive genes are not controlled by a separate circadian clock.

Even more interesting, the researchers found that the transcriptional patterns of light and temperature genes are offset by about six hours, with light peaking earlier than temperature — a pattern that mirrors the ups and downs of the natural environment, in which temperature is lowest around dawn and highest near sunset.

And what happens if the single clock gets conflicting light and temperature signals? Over the ranges that Boothroyd and Young tested, temperature turned out to be the weaker of the two stimuli. “If you give the fly appropriate phases of light and temperature, it maintains its activity as it would in light alone,” Boothroyd says. “But if you give it light and temperature in the opposite phases — light during cooler temperatures and darkness during warmer ones — the fly somehow has to choose which one to follow, and it chooses light.”

“The big message,” she says, “is that there is one molecular clock, which integrates information from both light and temperature. And it presumably relays that information to the rest of the organism.”

Citation: PLoS Genetics 3(4): e54 (April 6, 2007)

Source: Rockefeller University

Explore further: Circadian genes go to sleep every day at the periphery of the nucleus

Related Stories

A model for ageing

August 7, 2015

Life is short, especially for the killifish, Nothobranchius furzeri: It lives for only a few months and then its time is up. During that short lifespan it passes through every phase of life from larva to venerable old fish. ...

Recommended for you

New Horizons team selects potential Kuiper Belt flyby target

August 29, 2015

NASA has selected the potential next destination for the New Horizons mission to visit after its historic July 14 flyby of the Pluto system. The destination is a small Kuiper Belt object (KBO) known as 2014 MU69 that orbits ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.