Scientists complete first genetic map of a plant

A lab researcher gathers samples from thale cress, the first plant to have its genome completely mapped

December 13, 2000
Web posted at: 2:38 PM EST (1938 GMT)

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By Richard Stenger
CNN.com Writer

(CNN) -- A lowly weed has joined an elite club of organisms whose genomes have been completely sequenced, scientists announced Wednesday. Unlocking the genetic blueprint of the thale cress plant could lead to more productive crops and advances in medicine.

Officially known as Arabidopsis thaliana, the plant joins yeast, the nematode worm, the fruit fly and dozens of bacteria that have revealed their entire genetic structure to researchers.

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A spindly cousin of the mustard plant that thrives in dry, hilly climates in Europe, thale cress is an ideal subject in the genetic laboratory. The flowering plant is simple, easy to grow and produces up to eight generations of descendants in one year.

But it also contains genes found in more complicated cousins, molecular structures necessary to produce seeds, flowers and stave off infection.

The genome of Arabidopsis has about 25,000 genes, similar to the functional complexity of the fruit fly. Each Arabidopsis cell has five chromosomes that together contain about 120 million base pairs, the building blocks of the genome. In comparison, each human cell has about 3 billion.

Some of the newly identified Arabidopsis genes were involved in disease resistance. Others were extremely similar or identical to human genes linked to certain illnesses.

In June, geneticists announced that they had completed a rough draft of the human genome. A complete map could be published early next year.

"The completion of the Arabidopsis genome sequence has profound implications for human health as well as plant biology and agriculture," said Robert Martienssen of the Cold Spring Harbor Laboratory, one of the primary plant researchers.

Hundreds of scientists from the United States, Europe and Japan collaborated over five years to complete the DNA sequence. The journal Nature will publish their studies in the December 14 issue.

The thale cress plant is ideal for genetic research, due to its simple structure and rapid reproduction

Thale cress researchers still have plenty of mysteries ahead to unravel. The relatively simple plant surprised geneticists with its level of genetic duplication. For unknown reasons, more than 70 percent of its DNA is copied at least once somewhere else on the genome.

Besides tackling that puzzle, scientists hope to identify the biological role of each Arabidopsis gene, all 25,000 of them, within the next 10 years.

"With the genome in hand, the next challenge will be to unravel experimentally the roles of individual Arabidopsis proteins," said Stanford University researcher Virginia Walbot in a related Nature article.

Genetic research on the thale cress plant has already boosted yields of staple crops such as wheat, tomatoes and rice. Scientists hope more research will contribute to advances in such fields as evolutionary biology and medicine.

Critics have expressed concern that genetically modified plants could lead to dangerous risks to the environment and consumers.

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Cold Spring Harbor Laboratory
Nature
Genome Sequencing Center
Stanford DNA Sequencing & Technology Center
Arabidopsis Genome Initiative

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