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12/13/2000 08:00:00

Sequencing of Arabidopsis genome will havehuge payoffs, Caltech plant geneticist says

Whether or not the man was right when he said a mustard seed can move mountains, a poorer cousin of mustard named Arabidopsis has just been certified one of the heavy lifters of 21st-century biology.

With today's announcement that the international effort to sequence the Arabidopsis genome has been completed, plant biologists now have a powerful tool that is a triumph for biology as well as world agriculture, says Caltech plant geneticist Elliot Meyerowitz.

"Anything you learn in Arabidopsis is easily applied to crop plants," says Meyerowitz, in whose Caltech lab the first cloning and sequencing of an Arabidopsis gene took place.

"With knowledge from the genome sequencing, you might be able to make crops more resistant to disease and other plant problems," he said. "Fifty percent of all pre- and postharvest losses are due to pests, so if you could solve these problems, you could double the efficiency of world agriculture."

Arabidopsis is a nondescript weed of the mustard family that has a thin 6-inch-long stem, small green leaves, and tiny white blooms when it flowers. With no commercial, medicinal, decorative, or other practical uses, the plant is hardly even worth grubbing out of the flower bed when it springs up in its various habitats around the world.

But for geneticists, Arabidopsis is the powerhouse of the plant world. It is easy to plant and grow, maturing in a couple of weeks; it is small and thus requires little precious lab space; it is easy to clone and sequence its genes; and it produces plenty of seeds very quickly so that future generations—mutants and otherwise—can be studied. And now, Arabidopsis is the only plant species whose genome has been totally sequenced.

"Arabidopsis took off in the 1980s after it was demonstrated it has a very small genome, which makes it easier to clone genes," said Meyerowitz, a longtime supporter of and adviser to the international Arabidopsis genome project.

"One reason the plant was chosen was because it doesn't have that much DNA," he said. "Arabidopsis has about 125 million base pairs in the entire genome—and that's 20 times smaller than the human genome, and thus about 20 times less expensive to sequence. It's been a bargain."

The sequencing of the plant genome was originally proposed in 1994 for a 2004 completion, but experts later realized the project could be completed four years early—and under budget.

"Everybody shared the cost, and everybody will share the benefits—all the information is in the public domain," Meyerowitz says. "Taxpayers got a big bargain."

Sequencing Arabidopsis has benefits for the understanding of basic biological mechanisms, in much the same way that sequencing the roundworm or fruit fly has benefits. As a consequence of evolution, all organisms on Earth share a huge number of genes.

Thus, the information obtained from sequencing Arabidopsis as well as fruit flies and roundworms will contribute to advances in understanding how the genes of all living organisms are related. These underlying genetic interactions, in turn, will eventually lead to new treatments of human disease as well as the genetic engineering of agricultural products.

In addition to making crops more disease- and pest-resistant, genetic engineering could also change the time of flowering so that crops could be fitted to new environments; make plants more resistant to temperature changes; and possibly lengthen the roots so that plants could make more efficient use of nutrients.

Also, approximately one-fourth of all medicines were originally derived from plants, Meyerowitz says. So better understanding of the enzymes that create these pharmaceutical products could be used for creating new drugs as well as making existing drugs better and more efficient.

Contact: Robert Tindol (626) 395-3631