First plant genome sequence

GENETICS REACHED a major milestone today as an international research team announced it has completed the first plant genome sequence.

The species Arabidopsis thaliana has emerged as the plant counterpart of the laboratory mouse, offering clues to how all sorts of living organisms behave genetically, with potentially widespread applications for agriculture, medicine and energy.

This achievement, by a consortium of scientists called the Arabidopsis Genome Initiative (AGI), was reported in the journal Nature. It published four articles describing how researchers sequenced the entire genome of this weed in the mustard family.

Because it is a model for over 250,000 other plant species, Arabidopsis is yielding insights that scientists are already applying to make other plants easier to grow under adverse conditions and healthier to eat.

For the once-humble Arabidopsis, simplicity is truly a virtue. Its entire genome consists of a relatively small set of genes that dictate when the weed will bud, bloom, sleep or seed.

Those functional genes have their counterparts in plants with much larger genomes, such as wheat, corn, rice, cotton and soybean.

Unlike the human genome, Arabidopsis has few "junk" DNA sequences that contain no genes. The plant is practical for scientists because it matures quickly, is small and reproduces abundantly.

All these physical and genetic traits add up to an especially useful organism whose genome is now catalogued for the public's benefit.

"The Arabidopsis genome is entirely in the public domain, so the research results being announced today are immediately available to scientists across the world," said Daphne Preuss, an advisor to the AGI and a faculty member in the University of Chicago's Department of Molecular Genetics and Cell Biology. "Because its implications for farming, nutrition and medicine are potentially vast, this plant has gradually become quite indispensable to us."

The complete sequence of Arabidopsis is directly relevant to human biological functions, because many fundamental life processes at the molecular and cellular levels are common to all higher organisms.

Some of those processes are easier to study in Arabidopsis than in human or animal models. Arabidopsis contains numerous genes equivalent to those that prompt disease in humans - ranging from cancer and premature aging, to ailments such as Wilson's disease, in which the human body's inability to excrete copper can be fatal.

One result of the research has been crops that are more resistant to the cold. Because every molecular function of plants is dictated by DNA, an understanding of the genome could also help scientists develop crops that grow faster and larger, are more disease-resistant, and produce useful chemicals more efficiently.

Arabidopsis researchers have also identified genes that determine whether the growing shoot of a plant will develop into a flower. By inserting a certain gene into poplar shoots, scientists have shortened that tree's flowering time from six years to only six months.

Plants hold great potential as sources of renewable energy, although they currently represent just three percent of U.S. energy resources. Completion of the Arabidopsis genome sequence is revealing how photosynthesis converts solar energy and carbon dioxide into biomass, helping scientists develop better plants for fuel and chemical uses.

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