LONDON - The genetic sequence of the small weed called Arabidopsis thaliana - the first flowering plant to have its genome sequenced - promises to deliver a "cornucopia of delights" to the scientific community, one member of the consortium that sequenced its genome predicted.

Michael Bevan, who is based in the UK, told BioWorld International, "The relevance of the sequence of the genome of this weed is that it gives us the keys to unlock all the processes that plants carry out. It will make the science go better and faster."

The sequences of the final three of the five chromosomes of A. thaliana were published in the Dec. 14, 2000, issue of Nature, those of the first two having been published last year. Members of the Arabidopsis Genome Initiative present a summary of their main findings in a paper in the same issue of Nature, titled "Analysis of the genome sequence of the flowering plant Arabidopsis thaliana." The consortium includes scientists working in France, the UK, Germany, the U.S. and Japan, who have been collaborating for over five years on the project.

Bevan, head of the Department of Molecular Genetics at the John Innes Centre in Norwich, UK, described plants as being of "compelling importance" in the world. "They provide all the food that we eat, many of the clothes that we wear, many building materials and a vast range of chemical products that we use as medicines," he said. "They make all these things by capturing energy from outside our planet, from the sun, and they take our waste product - carbon dioxide - and convert it into oxygen."

For reasons such as these, he predicted, knowing the sequence of Arabidopsis will have a "huge number of benefits."

Commenting on the milestone report in a News and Views article in Nature, Virginia Walbot, of the Department of Biological Sciences at Stanford University in Stanford, Calif., said that although some might think that it would be more useful to study a crop plant than "this tiny weed," Arabidopsis has many qualities that facilitate laboratory study.

In her article, titled "A green chapter in the book of life," she explained that the small size of Arabidopsis makes it easy to cultivate in the laboratory, and that most of this plant's developmental and physiological processes, and the genes controlling them, will have counterparts in crop plants.

One interesting line of inquiry, she added, will be to study the genetic differences between Arabidopsis and crop plants that were domesticated and selectively bred by humans. "Selection of traits that improve our diet and make harvesting easier have changed the pea-sized wild tomato into the modern giant, and the bone-hard teosinte seeds into the large, soft, modern maize. Studies of Arabidopsis will help to determine the genetic basis for these changes," she concluded.

Analysis of the Arabidopsis genome showed that it contains more than 25,000 genes. These encode proteins belonging to 11,000 families. This is, said the paper by the Arabidopsis Genome Initiative, a similar level of diversity to Drosophila (the fruit fly) and Caenorhabditis elegans (the nematode worm), the other multicellular eukaryotes that have been sequenced.

Bevan told BioWorld International, "This was many more genes than people had predicted, and scientists have so far determined the function of only a few of these genes. We also identified a lot of genes that have arisen from bacteria that were incorporated into the plant and which now make up the chloroplasts. Many of these genes were identified in the nucleus."

A further discovery is that the Arabidopsis genome had undergone a complete duplication at some point during its evolution, leading to its currently having a high number of closely related genes. In all, about 70 percent of the genome has been duplicated.

The next phase is to determine the function of all the genes that have been identified. In the U.S., the National Science Foundation is putting in $150 million for the first three years of the Plant Genome Award Program and the 2010 Program in Functional Genomes. The latter aims to determine the function of the 25,000 Arabidopsis genes by 2010.

One strategy for determining the function of the genes will be by site-selected mutagenesis, the consortium said. Bevan added that it also will become possible to carry out experiments to assay expression of all the genes of Arabidopsis at the same time.

Some useful genes already have been isolated. For example, researchers at the John Innes Centre, which is funded mainly by the UK's Biotechnology and Biological Sciences Research Council, already identified a gene, called FRIGIDA, that controls flowering time in Arabidopsis. This discovery may make it possible for plant breeders to develop winter and spring varieties of crops, depending on whether the varieties need a cold period to stimulate them to flower.

The research council also is funding research aimed at identifying natural disease resistance genes that have been lost from the Brassica (cabbage) family as a result of selective breeding. Once these genes have been identified in Arabidopsis, it may be possible to restore natural resistance to diseases in Brassicas, and reduce reliance on chemical methods of disease control.