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A gene for curvaceous cuisine

The secret to pear-shaped fruit lies in a genetic mutation that can transform normally round produce into elongated oddities, researchers say in a new study.

The abundance of pear-shaped fruits is probably a modern phenomenon related to our preference for curvy cuisine such as plum tomatoes, eggplants, and squash. Only domesticated plants grow pear-shaped fruits.

"You just don't find pear shapes in the wild—nature seems to love nice, small round berries," says Steven D. Tanksley, who led the study at Cornell University in Ithaca, New York.

In the wild, spherical fruits like apples and grapes have seeds in the center, which increases the chances that they will be dispersed when an animal takes a bite.

The first descriptions of pear-shaped tomatoes appeared in scientific journals nearly a century ago, and in the 1920s scientists identified a genetic region linked to the shape of fruits. These early horticulturalists searched for the mechanisms that control the growth of tomatoes and the development of different varieties of fruit.

Now, Tanksley and his colleagues seem to have found one: a mutation in a gene called OVATE. The disabled gene creates a partially formed protein that causes abnormal, elongated fruit.

To show how OVATE works, the researchers inserted a normal copy of the gene into a tomato plant: Instead of pear-shaped tomatoes, the plant grew round fruits.

Since its discovery, the OVATE protein has been found in other plants, including rice. The researchers predict that the OVATE gene could have "a broad influence on plant development" and may belong to a family of genes that regulates growth. A small number of genes may contribute to rapid shifts in plant growth and evolution.

Tanksley suspects that a single, recent genetic change could have sparked the evolution of pear-shaped fruits. His laboratory is now investigating the OVATE gene mutation in fifty different types of pear-shaped tomatoes.

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Liu, J. et al. A new class of regulatory genes underlying the cause of pear-shaped fruit. Proc Natl Acad Sci USA. Published online September 19, 2002.

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