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COP1 protein may spur sprouting.

When the tip of a tiny seedling pokes out of the ground into bright sunlight, profound changes take place. The hooklike tip of the little plant's skinny white "stem" slowly straightens, as if stretching to meet the sun. Miniature leaves, until now pressed together like the palms of your hands, unfold and start to grow.

These first responses to light are "some of the most dramatic redirections of development that a plant will experience during its life," says Peter H. Quail, research director at the Plant Gene Expression Center, Albany, California.

Each of the changes is the work of phytochrome - molecules that sense light. Phytochrome turns on genes that cause seeds to sprout and plants to grow.

Scientists have now discovered a protein that acts as an intermediary between phytochrome and some genes. Named COP1, the protein is likely among the first in line to receive commands from phytochrome.

"The COP1 protein probably serves as a master switch, directing genes to carry out phytochrome's commands," says Quail.

COP1 experiments may reveal new secrets about the little-known inner workings of phytochrome. And the tests may pave the way to modifying not only this protein, but also others that phytochrome influences and directs.

"We may be able to change phytochrome's instructions," notes Quail. "Perhaps tomorrow's genetic engineers could rebuild COP1 or other phytochrome-controlled proteins to create new plants that sprout, grow, and flower when people - not nature - need them to."

One possibility: futuristic plants that sprout sooner than their weed competitors. That would help crops beat weeds in the race for light, nutrients, and room to grow and would potentially reduce the need for herbicides.

Quail and colleague Xing-Wang Deng, now at Yale, discovered COP1 in laboratory tests with a mustardlike plant, Arabidopsis thaliana. The experiments, Quail says, show that COP1 "is at the apex of a cascade of signals."

Seedlings lacking the COP1 protein offer proof of its role in their counter-parts. When grown in the dark, alongside normal seeds, those missing COP1 sprouted and grew as if they were in sunlight.

Inside the normal seedlings, however, COP1 repressed precocious growth. The ordinary seedlings wouldn't open their leaves until they found daylight.

Without Arabidopsis to serve as a lab and greenhouse model for these and other investigations of phytochrome, says Quail, COP1 and other pieces of the phytochrome puzzle might still be missing. Arabidopsis plants, white-flowered and about 10 inches high when mature, grow quickly, produce an abundance of healthy seeds, and are blessed with a very small genetic makeup.

Arabidopsis has about 100 times less genetic material than a wheat plant, for example," says Gerald G. Still, director of the Plant Gene Expression Center. "Arabidopsis has become the |lab rat' in plant biotechnology because we can learn a lot - in short order - from it. And everything we find out from Arabidopsis genes could be used in genetically engineering all kinds of plants, whether they grow in a field, an orchard, or your backyard."
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Author:Wood, Marcia
Publication:Agricultural Research
Date:Jul 1, 1993
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