UPTON, NY When the first warm rays of springtime sunshine trigger a burst of new plant growth, it's almost as if someone flicked a switch to turn on the greenery and unleash a floral profusion of color. Opening a window into this process, scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory and collaborators at the University of Wisconsin, Madison, have deciphered the structure of a molecular "switch" much like the one plants use to sense light. Their findings, described online in the Proceedings of the National Academy of Sciences the week of May 31, 2010, help explain how the switch works and could be used to design new ways to modify plant growth.
Previous studies showed that the light-sensing structure, called a phytochrome, exists in two stable states. Each state is sensitive to a slightly different wavelength, or color, of light from red to "far red," which is close to the invisible infrared end of the light spectrum. As the phytochrome absorbs photons of one wavelength or the other, it changes shape and sends signals that help plants know when to flower, produce chlorophyll, and grow.
"The phytochrome is almost like nature's light switch," said Brookhaven biophysicist Huilin Li, who is also an associate professor at Stony Brook University and a lead author on the study. "Finding out how this switch is flipped on or off by a signal as subtle as a single photon of light is fascinating."
As with all biological molecules, one key to the phytochrome's function is its structure. But scientists trying to get a molecular-level picture of a phytochrome have a formidable challenge: The phytochrome molecule is too dynamic to capture in a single image using techniques like x-ray crystallography. So, scientists have studied only the rigid and smaller pieces of the molecule, yielding detailed, but fragmented, information.
Now using additional imaging and computational techniques, the Brookhaven
|Contact: Karen McNulty Walsh|
DOE/Brookhaven National Laboratory