Tiny Weed Assumes Giant Scientific Status

LONDON, United Kingdom, December 13, 2000 (ENS) - It is not much to look at, but Arabidopsis thaliana, a weed otherwise known as thale cress, is about to broaden our understanding of how plants and animals grow, deal with disease and interact with their environment.

Tomorrow in the international weekly journal Nature, scientists present the results of a 10 year project known as the Arabidopsis Genome Initiative. The initiative set out to fully sequence a plant genome. The genome is an organism's total complement of chromosomes - its DNA (deoxyribonucleic acid) - including all genes and connecting structure.

A. thaliana

Arabidopsis thaliana is a weed which often grows in garden paths and walls. It is related to the mustard family. (Photo courtesy Millar Research Group, University of Warwick)

Scientists believe that Arabidopsis thaliana's DNA blueprint provides a model for the genetic basis of plant behavior common to all botanicals. It is the first complete catalog of all the genes involved in the life cycle of the typical plant, from seed to flower to fruit.

Arabidopsis thaliana, a small plant in the mustard family, was chosen because it offers many advantages for detailed genetic and molecular studies. It is plentiful, growing between the Arctic and Equator; small, with leaves between one and five centimeters long; and lives only six to eight weeks.

Most importantly, it has a small genome. A small genome helps simplify the task of determining the exact sequence, or order, of the four chemical sub units that make up DNA. Every plant gene is composed of a unique sequence of at least a thousand of these sub units, or bases.

It has taken 15 laboratories from the European Union, the United States and Japan a decade to sequence 115 million base pairs, encoding nearly 26,000 genes - more than any other genome to be completely sequenced so far.

The project has hastened the discovery of important genes in crop plants. Participating scientists have posted base sequences to GenBank, an up to the minute Internet compilation that also displays mouse, human, and other sequences as they become known.

Scientists can use GenBank to look for sequences other organisms have in common. Because similarities in sequence often indicate similarities in function, searching for sameness via computer quickens the discovery of a gene's function.

Once biotechnologists discover the sequence and function of a gene, they may be able to move useful genes into plants that lack them, such as a gene for disease resistance, for example. Or they might be able to rebuild a gene to boost its effectiveness.

In February's edition of Nature, for example, researchers announced how Arabidopsis thaliana can be genetically modified to remove the toxin methylmercury from contaminated soil. Known as bioremediation, plants and bacteria are increasingly being used in this way to deal with contaminated soils or waters.

A. thaliana

Tissue-cultured Arabidopsis thaliana. (Photo by Keith Weller, courtesy United States Department of Agriculture)
The findings published tomorrow will have implications that go beyond basic science. Scientists found striking similarities with animals and humans, which point to wide ranging future applications of this work to numerous fields from medicine to engineering.

"This remarkable accomplishment may pave the way for increasing agricultural productivity by improving crop yields and quality to help maintain a global food supply while protecting the environment," said U.S. Agriculture Secretary Dan Glickman.

The Arabidopsis Genome Initiative is funded by a variety of sources, including the National Science Foundation, U.S. Department of Energy, and Agriculture Research Service in the U.S. The European Union provided annual research grants of 26 million Euros (US$22.8 million) toward the initiative.

Researchers will now attempt to discover what job each of the 26,000 genes does. This will be the focus of the Multinational Coordinated Arabidopsis 2010 Project.

The project, according to its mission statement, will "exploit the revolution in plant genomics by understanding the function of all genes of a reference species within their cellular, organismal and evolutionary context."

For more on the 2010 project, visit: http://www.arabidopsis.org/workshop1.html