A major leap forward in plant science is reported for the first time today in the scientific journal Nature. An international research group of over 200 scientists, from 35 laboratories, who have been working on the tiny weed Arabidopsis thaliana (thale or common wall cress) have published the complete genetic map for 2 of this plants 5 chromosomes. The map consists of a complete DNA sequence* for chromosomes 2 and 4 of Arabidopsis.
"Arabidopsis was chosen as the subject of international efforts to sequence an entire plant genome in 1996" said Professor Mike Bevan of the John Innes Centre**, Norwich. Professor Bevan, Coordinator of the chromosome 4 sequencing work, went on "this apparently unlikely choice was based on the fact that Arabidopsis has a relatively simple genome, which is, for example, nearly 1/20th the size of the maize genome. It has also been the subject of much research because its small size and rapid growth make it a convenient model plant for laboratory work. This report describes the first 2/5ths of the sequence and we expect to complete the whole genome by the end of 2000."
Many important crop plants have large and complex genomes and these would require huge amounts of time and resources if they were to be analysed directly. Instead scientists decided to begin with the small and relatively simple genome of Arabidopsis and to use the information gained about Arabidopsis genes, and their functions, as a starting point in studying a wide range of crop plants.
"This strategy has been a great success" said Professor Bevan. "Many Arabidopsis genes, when transferred into distantly related plants such as wheat and rice, are found to perform the same functions in many different plants." A variety of genes controlling disease resistance, environmental adaptions such as cold tolerance and sensing of the seasons, plant shape and structure and the production of important food materials such as vitamins, fats and starch have been identified in Arabidopsis. These are providing new fundamental knowledge of important processes and the means to produce crop plants with enhanced nutritional content, disease resistance and environmental adaptability.
Different strains and eco-types of Arabidopsis grow successfully in a wide range of climates from northern Sweden to the tropical Cape Verde Islands. It will now be possible to identify and understand the genetic variation underlying the ability of Arabidopsis to adapt to this wide range of different growing conditions.
The research programme will cost approximately £30 million when completed, and is part of a public funded project, with the main funding supplied by a National Science Foundation ***(NSF) Cooperative Agreement and the European Commission****. Significant funding has also been provided by the BBSRC***** in the UK.
The project has so far completed nearly 70% of the 130 million base genome of Arabidopsis. This report describes the assembly of 37.1 million base pairs to assemble chromosomes 2 and 4 of the Arabidopsis genome. The assembled sequences represent the whole chromosomes with the exception of a small central region called the centromere. This region is characterised by very complex sequence repeats that currently are confounding the scientists attempts to assemble them in the correct arrangement. Analysis of the sequence has revealed 7,781 genes, and this represents approximately 30% of the predicted 26,000 genes that scientists expect to find in a complete plant genome. In contrast, a similar sized region of the human genome, chromosome 22, revealed only 545 genes, demonstrating that sequencing the small genome of Arabidopsis provides a very rich harvest of information.
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