以下文章選自New Scientist News 2000.12.14
The first complete DNA sequence for a plant could have more impact than its human equivalent
A frail weed related to swedes, cauliflowers and brussel sprouts has earned a place in history by becoming the first plant to have its DNA completely sequenced.
Researchers involved in the $70 million international sequencing effort announced their breakthrough on Wednesday at press conferences in London, Brussels, Washington DC and Tokyo.
Arabidopsis thaliana, known as thale cress, is just a few centimetres high, and grows throughout the world, from the Arctic Circle to the equator. Plant geneticists love it because it is small, grows to full size in weeks and is easy to tinker with genetically. Its genome is tiny - the human genome is thirty times larger - but contains the genetic secrets of all flowering plants.
The weed's entire set of 26,000 genes has now been laid bare and researchers expect unparalleled insights into how plants work, how they evolved, and what makes them different to all other life on the planet.
Plant breeders will be able to use the plant's DNA blueprint to accelerate the development of crops which produce food more efficiently and which protect themselves against pests.
"I think it's definitely more important than the human genome," said Ottoline Leyser, a key member of the worldwide Arabidopsis consortium based at the University of York. "Plants are fundamental to all ecosystems, and they provide the energy input."
Leyser believes the plant genome will help alleviate malnutrition by improving the quality and availability of food. She says this may save more lives than drugs developed with the knowledge from the human genome project, completed as a working draft in June 2000.
The 300 researchers across the world who collaborated in the Arabidopsis Genome Initiative began sequencing the weed's five chromosomes in 1996 and finished in October, four years earlier than anticipated. Their results appear this week in Nature (vol 408, p796, p816, p820 and p823).
They discovered that almost 60 per cent of the weed's genes are duplicated. This is because 100 million years ago, it took up an extra set of its own chromosomes. The researchers believe that plants do this to give themselves extra genetic flexibility, allowing evolution of new traits without sacrificing a gene's original function.
Tidal wave of knowledge
Armed with the entire blueprint, researchers expect to unleash a tidal wave of new knowledge about plants. "From this point on, plant science will never be the same," says Mike Bevan, European coordinator of the Arabidopsis consortium at the John Innes Centre in Norwich. "We can now design a new plant on paper, grow it in the lab and put it out in the field," he says.
And with 99.5 per cent of the DNA accounted for, researchers can rapidly pinpoint individual genes. They can even scan the whole genome at once to investigate traits which rely on combinations of genes operating together.
Once researchers identify genes which influence traits such as resistance to pests or thriftier use of nutrients, these can be transferred to crop plants through genetic engineering. Genetic engineering could be avoided by screening wild relatives of crop plants for the same genes. These could then be cross-bred into crop relatives through traditional breeding.
"It'll add considerable refinement and predictability to GM processes," says Chris Lamb, director of the John Innes Centre. Leyser adds: "Now we can eliminate unknowns about GM. It's a win-win situation, with better genes and better information about how they work."
In 2004, rice is likely to become the second fully sequenced plant, chosen because it's a major food staple.
More at: Arabidopsis Genome Initiative Further detailed analysis of the sequencing of Arabidopsis is featured in New Scientist magazine on 16 December.
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1900 GMT, 13 December 2000