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United States Department of Agriculture

Agricultural Research Service

"Jumping Genes" and the Color of Grapes

We've all seen "red" grapes. (They're really kind of a reddish-purple.) We've also seen "white" grapes. (Their skins are kind of light green.)

But why are they different colors? Why aren't all grapes red? Or white?

You can chalk much of that up to what scientists like Agricultural Research Service (ARS) researcher Christopher Owens call a "jumping gene." Owens is a gene scientist in the ARS Grape Genetics Research Unit at Geneva, New York.

Genes carry physical features of plants and animals from parents to their offspring. Owens and researchers with France's National Institute of Agricultural Research in Montpellier, France, recently unlocked some of the secrets about what makes a grape red or white.

Among the important things they discovered was why a gene that's found inside all grapes--it's called (are you ready for this?) VvmybA1--plays such a big role in the color of a grape.

Not too long ago, scientists in Japan found that VvmybA1 helps determine why white grapes turn out white.

Owens and his team showed that it's actually the presence--or absence--of a tiny, movable piece of the VvmybA1 gene that's responsible for a grape's color.

This movable jumping gene is what scientists call a "genetic mutation," or accidental change.

Think of Footprints

How does this work? Think of yourself standing in a field covered by an inch or two of fresh, untouched snow--or perhaps in front of the smooth, wet sand closest to the water on a favorite beach--before anyone else has had a chance to walk there.

If you decide to be the first to walk on this field of snow or on this smooth, wet sand, you'll disturb it by changing its appearance with your footprints! The change may seem minor, but it's still a change. In the case of the snow field, the spots marked by your footsteps may be the first to melt if no one else goes into that field.

What's That Got To Do With Grapes?

The jumping gene that causes the color mutation in grapes was named "Gret1."

“When Gret1 ‘visits’ and then leaves parts of the gene, it slightly changes the surrounding material, like the footprints in the snow," says Owens. These changes make the VvmybA1 gene slightly different--and different enough to affect the color of the grape.

Owens explains that grapes have two copies of every gene. “When Gret1 is present in both copies of VvmybA1, the grapevine will bear white fruit,” he says.

This is big news, because color is perhaps the most important of grape characteristics. It's one of the first things people think of when deciding to plant or buy grapes for eating, or for juice or wine. Also, grape color has been linked to some of the health benefits from eating grapes.

Owens says that the discoveries about VvmybA1 and Gret1 may make it easier to grow new types of grapes for specific colors. Another possibility is to develop new grapes with unusual colors.

“Picture it,” Owens says: “an orange grape!”

By Luis Pons, formerly Agricultural Research Service, Information Staff
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Last Modified: 2/14/2011
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