A small weed has made history by becoming the first plant to have its entire genetic code read by scientists.

Arabidopsis thaliana, or thale cress as it is commonly known, may not be the most exciting plant to look at, but researchers believe the information hidden in its DNA will have a profound impact on all our lives.

Plants are fundamental to all ecosystems in the world - they are the energy inputs of those systems

Dr Ottoline Leyser, UK Arabidopsis researcher

From the genes in this plant, which will grow happily on waste ground by the side of the road, scientists have already learned how to protect wheat from disease and to double the yield of oilseed rape.

But having the complete "life code" of Arabidopsis thaliana will not only accelerate discovery in plant biology, it may even give researchers new insight into human health - some of the plant's genes look very similar to the faulty genes that cause disease in us.

The decoding work, which has taken more than four years of intensive study and cost $60-70m, was a collaborative effort involving laboratories across the globe.

Landmark in science

At separate conferences in different world capitals, the scientists involved attempted to sum up the significance of their work.

Dr Daphne Preuss, assistant professor of genetics and cell biology at the University of Chicago, who helped oversee the US contribution to the research, said: "This landmark achievement means that every lab around the world working with Arabidopsis, as well as any other flowering plant, will be doing their science faster, easier and in a more thorough way."

In the UK, researchers suggested that the plant genome was arguably more important than the human genome which is soon to be completed.

"Plants are fundamental to all ecosystems in the world - they are the energy inputs of those systems," said Dr Ottoline Leyser, from the Genomic Arabidopsis Resource Network, York University.

"But even if you take a human-centric view, the plant genome is still more important because far more people die from malnutrition than die from the diseases the human genome will help target."

Four letters spell life

To decode the Arabidopsis genome, researchers had to read the 115 million chemical "letters" strung out along the DNA spirals in the plant's cells. The DNA itself is wound on to five separate structures, or chromosomes.

The research has been published in the journal Nature

Written in the code, the researchers believe, are more than 25,000 genes, the templates that cells use to make proteins.

These are the large molecules that build and maintain the plant, that determine its life cycle from germination to seed production.

One of the most surprising findings to come out of the research is just how much the Arabidopsis genome repeats itself. Less than half of its DNA is unique - the rest is copied at least once somewhere else in the genome.

Nevertheless, the Arabidopsis thaliana genome is small. The human genetic package, for example, is over 25 times as big.

Economic value

Even among plants, Arabidopsis is tiny - its genome is nearly 1/20th the size of maize. Indeed, its smallness was one of the main reasons why the lowly weed was chosen for the international decoding project.

Arabidopsis profile

Common names include thale cress or mouse eared cress Belongs to the Brassicaceae (mustard or crucifer) family A few centimetres high Has a rapid life cycle (6 weeks) and prolific seed production Likes a temperate climate and open free-draining ground Frequently found growing on wasteland by carparks and railway sidings

But its short life cycle and prolific seed production have also helped to make the plant a popular and convenient model in which to test ideas in laboratory work.

And now, by decoding the complete sequence, scientists are in a better position to modify and improve other plants that have economic value, such as soyabean and maize.

This could help make them less prone to disease and more resilient in growing conditions that are less than favourable. It is likely also to result in foods that last longer on supermarket shelves, are lower in fat or higher in protein, or which simply taste better. Plants will give us new materials and novel drug products.

Scientists will also want to compare the Arabidopsis sequence to other fully (or largely) sequenced genomes, including those of yeast, fruit flies and even humans.

Knowing the locations and functions of Arabidopsis genes can help researchers pinpoint similar human genes and learn more about the causes of disease.