Future green: Plant's gene code is mapped in world first
Copyright 2000 Agence France Presse
December 13, 2000
Richard Ingham
PARIS, Dec 13 - An international group of scientists announced Wednesday they had cracked the first genetic code of a plant, an achievement that could throw open the gates to a new "green revolution" of supercrops.
The object of their study is a humble cousin of the cabbage -- a tiny flowering plant called Arabidopsis thaliana, also known as thale cress.
More is known about this otherwise unremarkable species than any other plant. It is a lab favourite because its five chromosomes make it small and relatively simple, yet its basic processes are mirrored across the plant kingdom.
Under a project launched in 1996, a consortium of public- and private-sector scientists from the United States, the European Union (EU) and Japan set up the Arabidopsis Genome Initiative, setting 2000 as the goal to unravel the plant's genetic structure.
The sequencing of chromosomes 2 and 4 were published last year, and 1, 3 and 5 are published in Thursday's issue of Nature, the British science weekly.
They describe 25,498 genes that control 11,000 types of proteins, the very ingredients and mechanisms of life.
Flowering plants came into being about 200 million years ago, which is very recent in evolutionary terms.
This means that their physiological processes, in drawing nutrients and water from the soil, light and carbon dioxide from the sky, are similar and they mainly share the same genes to do it.
Figuring out Arabidopsis's genetic workings will therefore give insights into all the plants that sustain humanity -- from grasses that support livestock to soybean, wheat, corn and fruit and other crops that are direct sources of food.
The prize
to boost yields to help feed the world's six billion mouths, make crops more resistant to pests, able to cope with droughts or floods caused by climate change -- perhaps even create foods with built-in vaccines to combat disease.
"Productive paths of crop improvement, based on enhanced knowledge of Arabidopsis gene function, will help meet the challenge of sustaining our food supply in the coming years," the Arabidopsis group wrote.
Such goals do not come without controversy, however.
In the past five years, plant genetics has come under attack from ecologists, who fear the next green revolution could have a catastrophic effect on the environment.
Their fear is that genes from these novel crops could pollinate other plants, wreaking fundamental changes in wildlife such as creating "superweeds" that are resistant to herbicides.
So far, there is little scientific evidence to back this although most experts agree transgenic crops have been around for such a short while that no-one can safely predict their long-term impact.
Plant biologists point out that understanding a plant's mechanisms also opens the way to better cross-breeding without genetic engineering, in the way that mankind has done for thousands of years.
"We started domesticating wild plants only 8,000 years ago, from some rather unpromising wild progenitors," Virginia Walbot, of the Department of Biological Sciences at Stanford University, California, said in a commentary in Nature.
"Selection of traits that improve our diet and make harvesting easier have changed the pea-sized wild tomato into the modern giant, and the bone-hard teosinte seeds into the large, soft modern maize.
"Studies of Arabidopsis will help to determine the genetic basis for these changes," she said.
Deciphering Arabidopsis is the latest in a string of biotech breakthroughs this year, the greatest of which was the completion of a rough draft of the human genetic code, published on June 26.
As with each of these enormous projects, the next step will be to sift through the mountain of data to determine what the genes do and how they work.
A scheme called the 2010 Project is seeking 500 million dollars over the next decade to explore Arabidopsis' genome extensively and set up a four-dimensional database.
ri/bm
Thale cress is the wallpaper of plants: a tiny, inedible weed so ubiquitous, for it grows almost around the world in dry, open soil, that it has become almost invisible.
But it is precisely these tedious characteristics that has made Arabidopsis thaliana the darling of plant biologists.
Biotechnologists who unveiled Arabidopsis' genetic structure Wednesday say the plant is an ideal choice because it is so small -- and thus easy to study -- yet it contains in miniature all the important functions of crop plants.
Corn, rice and fruit trees have a DNA map that is hundreds or thousands of times bigger than Arabidopsis' 26,000 genes, distributed over five chromosomes.
But the physiological processes, and the genes that control them, are largely the same.
Arabidopsis' minute size and short lifecycle means a trayful of the plants is like a field in microcosm.
Researchers can work in safe, controlled conditions if they want to insert genes or change light, soil and nutrients to see how these can affect a plant's growth and yield.
They can also introduce bacteria, viruses, funguses and insects to understand how a plant is invaded and how it resists.
One thing that has astonished scientists is that more than two-thirds of Arabidopsis' genes are duplicates.
Only about 15,000 genes are different -- a tally that is in the same ballpark as other well-studied basic organisms, such as the nematode worm and the fruitfly.
The supposition
multi-celled creatures or plants beyond the level of fungus or bacteria need at least 11,000 different genes to have the tools to adapt and survive.
But why Arabidopsis has so many apparently excess genes is unclear. Either these genes are redundant or play some evolutionary role, which means the plant is more complex than thought.
One eagerly-explored path will be the genes that control communications between Arabidopsis' cells.
Unlike animals or insects, plants cannot move in response to a change in environment, and so are forced to adapt to different conditions.
Arabidopsis has several hundred proteins called receptor serine/threonine kinases that apparently provide signalling pathways, creating a fantastically sensitive mechanism for monitoring light, temperature and water.
Arabidopsis is related to mustard plants, Brussels sprouts, cauliflower and cabbage and other vegetables.
These are all members of the brassica family, but only exist separately thanks to human selection that began with a single species, Brassica oleracea, thousands of years ago.