- Number 314 |
- June 21, 2010
Scientists decipher structure of nature’s ‘light switch’
Left: 3-D phytochrome map;
Right: Fit-together fragments
forming two sister units (one
shown as ribbon, the other in
space-filling format), revealing
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 DOE's Brookhaven Lab and collaborators at the University of Wisconsin have deciphered the structure of a molecular “switch” known as a phytochrome that is much like the one plants use to sense light. They used a combination of electron microscopy, cryo-electron microscopy, and computational techniques to produce a 3-D map of the full structure. They then used this map to piece together the detailed structures of small phytochrome fragments that had been previously determined using x-ray crystallography.
The new structure revealed a long twisted area of contact between two individual “sister” units, with a good deal of flexibility at the untwisted ends. This structure supports the idea that the absorption of light somehow adjusts the strength or orientation of the contact, and through a series of conformation changes, transmits a signal down the length of the molecular interface. Understanding how these changes in shape send signals that help plants know when to flower, produce chlorophyll, and grow may help scientists design new ways to modify plant growth.
[Karen McNulty Walsh, 631.344.8350,