Scientists Decode Plant Chromosomes
by
Scott Neuman,
Associated Press Writer

2:02 PM EST; December 15, 1999; (AP) -- Scientists have decoded the DNA of a complete plant chromosome for the first time, a milestone in understanding the deepest secrets of the plant kingdom and a step toward developing improved crops. Researchers unraveled the genetic structure of two chromosomes from Arabidopsis thaliana, a member of the mustard family. That meant identifying millions of building blocks that make up the chromosomes.

Arabidopsis has long been a favorite subject for the study of plant genetics, because its genome -- the complete collection of its DNA -- is relatively small. It is also an ideal model for gaining insights into 180,000 other flowering plants, including corn, wheat, and rice. Two research teams, one in the United States and the other in Europe, published the results of their work in Thursday's issue of the journal Nature.

Earlier this month other scientists announced the first sequencing of a human chromosome. Researchers are working to sequence the entire Arabidopsis genome. "By sequencing Arabidopsis, you can use that information to infer the basic set of genes that make up any plant," said Michael Bevan of the John Innes Center in Norwich, England. He is coordinator of the European Union team that sequenced Arabidopsis Chromosome 4. Arabidopsis Chromosome 2 was sequenced by a team at the Institute of Genomic Research in Rockville, MD. Scientists expect to sequence all five Arabidopsis chromosomes by next Summer. That will be an important trial run for the sequencing of bigger plant genomes, like those of corn and rice, which should contain many of the same genes. "It is not only a trial run, it has almost the same parts list," said Elliot Meyerowitz, a biologist at the California Institute of Technology who was not involved in the newly reported Arabidopsis work.

Deciphering the genome of agricultural plants could lead to new genetically engineered strains with improved nutritional value and resistance to disease and pests. The issue of genetically altered food has sparked controversy in Europe and elsewhere. For both Arabidopsis chromosomes, about half of the genes uncovered during sequencing have "no known function." That is about the same percentage of mystery genes being found in human and animal genomes, said J. Craig Venter, Chairman of the Rockville-based Institute. Dr. Venter said the large number of Arabidopsis genes with unknown functions means "we know only a small portion" of plant biology. However, "Genes governing such basic processes as cell division are almost identical in plants and animals, strongly suggesting that both descended from the same ancient one-celled organism that lived about 1.5 billion years ago," Venter said. "Some people like to imagine that evolution is only a theory, but all you have to do is look at the DNA level to see that these are real events that took place a long time ago," he said.