Scientists Draft Maps of Rice Plant Genome
Once Refined, Research Could Lead to Hardier Grains That Boost World's Food Supply
By Justin Gillis
Washington Post Staff Writer
Friday, April 5, 2002; Page A05
Scientists announced yesterday they had created the first comprehensive genetic maps of the rice plant, and -- in yet another blow to mankind's ego -- they discovered in the process that rice appears to have more genes than people do.
Researchers hailed the new maps, compiled by separate teams in China and California, and said they would likely eventually enable scientists to engineer hardier, higher-yielding varieties of rice to feed a rapidly growing world population. Moreover, the scientists expect information gleaned from rice to be useful in improving other grains, such as wheat and corn, that are grown most intensively in the industrial world.
"It is a milestone for genetics and biology and, maybe ultimately, for preventing world hunger," said Francis Collins, director of the National Human Genome Research Institute in Bethesda, which was not involved in the work. "This is not only the genetic sequence of the grain that is most widely used in the world, it will greatly advantage research on the other grains, as well. And grains represent 60 percent of the calories consumed by the human race."
Perhaps the most surprising finding of the new papers is that the rice plant has as many as 50,000 or 55,000 genes, compared with an estimated 30,000 to 40,000 for a human being. The estimates for both species are still shaky, but the rice research, unveiled in today's issue of the journal Science, adds to a growing body of data saying that human beings are not alone when it comes to biological complexity.
In a commentary accompanying the new papers, Jeffrey L. Bennetzen, a biologist at Purdue University, suggested the finding was consistent with the overall pattern of scientific discovery since Nicolaus Copernicus. That Polish scientist's insistence that the Earth was not the center of the universe was the first in a series of revelations about the natural world that have jolted mankind's sense of being the pinnacle of Creation.
Despite precedent, Bennetzen said the new finding won't go down easily.
"Something about human nature apparently requires that, to view ourselves as a superior species, we must have the highest gene number," he wrote. "We will need to get over this, as there will be lots of 'lower' species . . . that have many more genes than humans."
Genes are units of heredity that provide instructions for making proteins, the working parts of a cell. Although scientists once equated the number of genes in an organism with its biological complexity, that idea is fast collapsing with new research.
In mammals, for example, it's becoming clear that a single gene can provide instructions for multiple proteins, with the machinery inside a cell slicing and dicing parts of proteins to make alternative forms. Scientists say it could well turn out that, while complex animals have fewer genes than many plants, they might have more types of proteins.
Rice, Oryza sativa, is the second plant and the first food crop to have its full genetic complement, or genome, described in the scientific literature. The first was a weed from the mustard family, Arabidopsis thaliana, that is a favorite of plant researchers. Described 15 months ago, it turned out to have fewer genes than people do.
The human genome was described in scientific papers little more than a year ago -- not long after that of the fruit fly, a crucial research organism. Work is moving apace on the mouse and the rat, other critical species in scientific research. Geneticists said this week they had been left dizzy by the acceleration of their own science, driven mainly by rapid improvements in the machinery they use to "read" genetic information.
The new genetic maps of rice are drafts, and they reveal a good deal less than the more complete Arabidopsis map. A separate international project to compile a complete, highly accurate rice map is underway. It could be completed within a year or two, at least five years ahead of schedule.
The papers represent, to some degree, the triumph of a scientific technique pioneered by Celera Genomics Corp. of Rockville. Instead of slow, painstaking, piece-by-piece analysis of a genome, the technique calls for shredding an organism's genetic material into bits, reading the genetic letters making up each tiny piece, and putting the whole thing back together, like a jigsaw puzzle, using the power of computers.
There is still disagreement about how well that technique works in producing highly accurate genetic maps, but there's not much question it can rapidly produce draft maps that are useful to researchers. That is essentially what the groups in China and California did.
The California work was done by a research institute in San Diego belonging to an agricultural company, Syngenta International Inc., and led by Steven P. Briggs and Stephen Goff. The Syngenta group, which has agreed in principle to make its data available to the international rice project, mapped the japonica strain of rice, commonly grown in the tropics.
The Chinese have already deposited their data with the international project. The Chinese paper is based on a map of the indica strain, grown in more temperate regions. The work was done by an institute in Beijing, led by Huanming Yang, that has existed only since 1999.The institute has rapidly staked out a place for itself in the world of cutting-edge genetics.
Moreover, it has become a point of national pride in China to make serious contributions to understanding rice. China is the world's most populous country, the biggest producer of rice, and the place where rice, originally a water weed, was domesticated about 7,000 years ago.
Scientists expect to put the new maps to work rapidly to help them find the genes that confer various traits, such as resistance to disease and drought. That knowledge might ultimately be used for genetic manipulation of the plant, they say, but more immediately it will be used to improve the efficiency of traditional cross-breeding.
The researchers hope they can produce a strain of rice that carries every favorable genetic trait for any given climate -- something that has been impossible with the slow methods of conventional plant breeding. They say such progress will be needed to feed an Asian population that could double by 2050.
Tantalizing as that prospect may be, the fact in their own paper that jumped out at the Chinese researchers was the comparison between rice and people.
"I'm sort of a human chauvinist pig, and I want to believe I'm superior to rice," said Gane Ka-Shu Wong, a researcher at the University of Washington who is part of the Chinese team. "But it seems to have more genes than me."
© 2002 The Washington Post Company
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