Within just a few years, commercial crops may acquire the ability to grow in salt-contaminated soil or to thrive through droughts, according to Daphne Preuss, a professor at the University of Chicago and an advisor/contributor to the Arabidopsis Genome Initiative (AGI), a team of researchers from the United States, Europe and Japan. 

AGI has just announced the first-ever complete sequencing of a plant genome: the small flowering mustard called Arabidopsis thaliana. Three years ahead of schedule, AGI wrapped up a multinational effort begun in 1996. The sequencing of chromosomes 2 and 4 was announced in 1999; as of December 12, 2000, the sequences of chromosomes 1, 3 and 5 were complete.

A close cousin of the table vegetables broccoli, cauliflower, kale and cabbage, Arabidopsis has no commercial use but has long been valued by scientists as the lab rat or fruit fly of the plant world. Considered a weed by some, Arabidopsis has attained star status by virtue of its simplicity. Its entire genome consists of a relatively small set of genes and relatively less "junk" DNA (sequences that contain no genes) than other more familiar or useful plants. It also matures quickly, is small and reproduces abundantly.

The news of the genome sequence conclusion, says Rita Colwell of the National Science Foundation (NSF) which partially funded AGI, "could well mark the beginning of a whole new plant-genomics industry." A model for all 250,000 other known plant species, Arabidopsis can help scientists develop crops that grow faster and larger, are more disease resistant, and produce useful chemicals more efficiently. Arabidopsis researchers have already inserted an Arabidopsis gene into poplar trees that shorted the trees flowering time from six years to six months.

Preuss' work at the University of Chicago has particular relevance to the transformation of commercial crops. Her team focused on the centromere, or middle of the Arabidopsis chromosome, which contains the "equipment" (cables or spindles) that transfers a copy of the chromosome into daughter cells during a partitioning process called mitosis. Centromeres have been especially difficult to work with, she notes, but "now we have more than five megabases of centromere sequences," she says, "more than anyone else has ever sequenced."

Her lab's next step is to "take bits of centromere and try to build chromosomes from scratch," she says. This work has special relevance to agriculture because it would enable researchers to insert genes and then remove them at will.

"Now when we take a gene from one plant and put it into another, we introduce it into the host cell's nucleus; the genes become integrated into the natural chromosome and cannot be removed," says Preuss. "If we can grow our own chromosome, we can transfer the trait in and out without disrupting the host plant's desirable traits."

Human medicine and the pharmaceutical industry will also obtain longer-term benefit from the Arabidopsis sequencing, says Preuss. The project has confirmed "what biologists have long intuited: all organisms are alike. This study drives it home: Half the plant's genome can also be found in humans," and many genes that are mutated in human diseases are found in plants, including one of the genes for breast cancer, she notes. "The basic cellular processes are shared by all organisms.

"But there are some things that Arabidopsis can do that humans can't," she says. "They make lots of amino acids and synthesize small molecules that humans can't. Since most of today's pharmaceuticals originated in plants, if we can harness the machinery in plants for synthesizing desirable compounds, we could achieve new drugs at lower cost and with fewer toxic byproducts.