Scientists involved in an international effort to sequence the entire genome of Arabidopsis thaliana have reported the first complete DNA sequence of a plant chromosome in the December 16, 1999, issue of the journal Nature. The results provide new information about chromosome structure, evolution, intracellular signaling and disease resistance in plants. The research conducted by U.S. participants was funded in large part by the National Science Foundation (NSF), as well as the U.S. Department of Agriculture and U.S. Department of Energy.
U.S. and European scientists in the Nature article report the complete DNA sequence of two of the five chromosomes of Arabidopsis. Working together, a U.S. consortium led by Cold Spring Harbor Laboratory scientist Richard McCombie, and the European Union Arabidopsis Genome Sequencing Consortium led by Michael Bevan of the John Innes Centre (Norwich, UK), completed the sequence of chromosome 4. A team of scientists at The Institute for Genomic Research in Rockville, Maryland, determined the sequence of chromosome 2. Together, these chromosomes comprise roughly one-third of the Arabidopsis genome. Scientists predict that sequencing of the entire genome will be completed by the end of 2000.
Says Mary Clutter, assistant director of NSF for biological sciences, "Scientists can use this information to understand the function of genes in important plant processes. These studies will ultimately lead to the development of plants that are more nutritious, produce useful chemicals,withstand flood and drought, or can grow on marginal lands. Considering how much we were able to learn about the genome organization at the chromosome level, we can look forward to many new discoveries next year when the entire genome is completed."
Arabidopsis thaliana has emerged as a powerful tool for research in plant molecular biology and genetics. The short generation time and relatively compact genome of Arabidopsis make it an ideal model system for understanding numerous features of plant biology, including ones that are of significant value to agriculture, energy, environment, and health.
"We are three or four years ahead of schedule," says McCombie, referring to the current progress toward the goal of completing the Arabidopsis genome sequencing project. "This is due largely to the fact that throughout this endeavor, all the groups involved have worked hard to share information."
Analysis of the chromosome 4 sequence and comparison of this sequence to that of chromosome 2 revealed several interesting features. The most striking is the extent to which individual genes and entire blocks of chromosomal regions have been duplicated in the Arabidopsis genome. For example, a very large stretch of DNA (4.6 million base pairs) is duplicated on chromosomes 2 and 4. This duplication represents approximately one-quarter of the total length of each of these chromosomes, and its existence in plants supports the emerging view that large-scale intragenome duplications may significantly impact genome evolution in many organisms.
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