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5 December 2013 11:26 am ,
Vol. 342 ,
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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How Flowers Know It's Spring
13 February 2004 (All day)
During the dark months of winter, plants keep busy monitoring the skies for signs of spring. Only when the days are long enough, a surefire indicator, do they begin to flower. Now researchers have figured out how a kind of molecular hourglass, filled and emptied each day, tells the plant that it's the season to blossom.
Many plants monitor and respond to day length. In Arabidopsis thaliana (thale cress), a popular experimental plant, the hours are tracked by a gene called CONSTANS. Levels of CONSTANS mRNA start rising about 12 hours after dawn, remain high throughout the night, then drop during the day. That means that during the short days of winter, it's expressed only when it's dark. On longer days, CONSTANS starts to crank up in the waning hours of daylight. Scientists have long suspected that those hours of light must do something to the CONSTANS protein to somehow let the plant know it's spring, but they didn't know how.
To unravel the mystery, George Coupland and colleagues at the Max Planck Institute for Plant Breeding Research in Cologne, Germany, decided to study the effect of light on the protein. They bred Arabidopsis plants engineered to keep CONSTANS mRNA levels high and found more CONSTANS protein during the light phase of long days than short days. That suggests that light helps preserve the CONSTANS protein and dark destroys it.
The next step was to examine the plants' photoreceptors, molecules that detect light of particular wavelengths. By creating plants that lacked various kinds of photoreceptors, then exposing them to light of a range of wavelengths, the team discovered what was going on. Photoreceptors sensitive to blue and far-red light--both components of sunlight--inhibit breakdown of the CONSTANS protein. In the reddish light of morning, however, another photoreceptor triggers the breakdown of the protein. That means only long days will allow the CONSTANS protein to accumulate to a high enough level to trigger other flowering genes, explains Coupland.
Although researchers knew that CONSTANS production levels varied, the new study shows that the protein is subject to "a whole other level of regulation ... that's controlled by these photoreceptors," says molecular biologist Mark Doyle of the University of Wisconsin, Madison. But he points out that as most of the experiments were done under monochromatic light, it's difficult to predict what the full suite of photoreceptors do in natural daylight.
Home page of George Coupland's group.