Inside Salk - October 2008 - page 6

Inside Salk October 2008
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 muchmore 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,
andmakes 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.”
Hunting for Missing Genes
All of these findings would not have been possible without studying
plant genetics, Chory says. But they were conducted by studying one
gene at a time to determine its function. That all changed beginning in
late 2000 when a team of scientists around the world completed the
Arabidopsis genome-sequencing project.
Joe Ecker,
a leading plant geneticist and professor in Salk’s Plant
Biology Laboratory, was part of a team of multi-national scientists that
helped sequence the plant’s approximate 25,500 genes. Knowing the
gene sequence now enables plant biologists worldwide to study the
genome as a whole, he says.
Having the genome sequenced doesn’t necessarily tell scientists
each gene’s function, however. But a major project in Ecker’s lab
recently funded with a $4million grant is chipping away at this
mystery. The long-term goal is to develop a database that describes the
role and cross-function of all 25,500 genes through a network of
researchers who will test mutant forms of Arabidopsis genes, a
Hundreds of Arabidopsis plants are grown in Salk’s greenhouses for research by scientists in the Plant Biology Laboratory.
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