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Arabidopsis Takes Root: Genetic Variation Studies

Chory joined the Institute in 1988 and brought a complementary perspective to plant research at Salk. While Lamb worked on plant pathogen interactions, Chory was interested in how plants perceive and respond to changes in their environment, particularly to light.

Stronger collaborations followed after Weigel joined the Institute in 1993.
Although they studied two different traits — Chory the emergence of seedlings from the soil and Weigel flowering time — both of these traits are influenced by light and are important for plants' fitness in the wild.

Following their work on the FT gene, they formed a joint program at Salk in 1998 to study genetic variation and adaptation using a collection of Arabidopsis strains from around the world. Taking advantage of differences among these strains, they identified additional genes that are involved in enabling Arabidopsis to adapt to various environments.

More surprising, however, was their discovery of the roles played by the plants' light-sensitive photoreceptors themselves.

"Variation in a number of different photoreceptors caused changes in flowering time or the sensitivity of a seedling to light," Chory explains. "This was unexpected because most people thought proteins that influenced gene expression would be the cause of variation observed in wild strains. It turns out that it's subtle differences in the photoreceptors themselves that nature selects for.

"We were able to show that plants from northern latitudes, such as Sweden, were much more sensitive to light than plants from latitudes close to the equator," she says. "An Arabidopsis plant from the Mediterranean has desensitized these pathways."

The finding was important because it provided the first clues to how crops could be developed to adapt to challenging environments, while also boosting yield.

Similar studies were being done elsewhere, says Weigel, who is now at the Max Planck Institute for Developmental Biology. But at the time, he and Chory formed one of three leading groups around the world that was studying genetic variation at the molecular level – 10 years before the subject became a hot topic in human biology research.

Among Chory's widely reported contributions is her lab's discovery that steroid hormones, called brassinosteroids, play an important role in plant growth and development. Genetic studies in Arabidopsis led to a new paradigm for how steroid hormones are perceived.

Her lab also found that brassinosteroids are a key element in a plant's response to light, allowing plants to adjust their growth to reach its light source or strengthen stems to support leaves. The potent hormone has applications in increasing yield in grain and fruit crops, and makes plants more resistant to drought and cold weather.

In contrast, reducing the naturally occurring steroid causes dwarfism. The idea that you can possibly control the height of grass, for example, drew strong attention from the media. The New York Times Magazine placed the finding at No. 2 in a June 11, 2000 story that ranked the Top 100 New Technologies. The headline read: "The Lawn That Never Needs Mowing."

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