Scientists Map Rice Genome:
Development Could Help Fight World Hunger

Marsha Walton,
CNN Science and Technology

April 4, 2002; Atlanta, GA ( CNN) -- Teams of scientists in China and Switzerland have sequenced the rice genome, a step that could someday lead to improving the quality of the crop that is a staple for more than half the world's population. This first complete genome sequencing of a crop plant is detailed in the April 5th Edition of Science, the Journal of the American Association for the Advancement of Science (AAAS).

Identifying the genetic code of rice "will speed improvements in nutritional quality, crop yield and sustainable agriculture to meet the world's growing needs," said Dr. Donald Kennedy, Editor-in-Chief of Science. As farmland shrinks and the world's population grows, researchers are trying to determine how to get more bang for their buck with each acre planted, crops with higher yields, more diverse nutrition and more resistance to pests and diseases.

Because rice is a principal source of nutrition for much of the world's population, understanding its makeup could help farmers develop plants that are more resistant to drought or more tolerant of other harsh conditions. "It is clear that genetic modification is the best approach for crop improvement," said molecular biologist Pamela Ronald of the University of California at Davis.

"Over the past 100 years, it has increased yields tremendously," said Ronald, a specialist in rice genetics who isolated the first disease resistant gene in rice in 1995. Ronald said "both traditional breeding and genetic engineering could be used to improve the plants, which produce more than 100,000 rice varieties.

'Preserve Diversity'

Other scientists express some cautions about genetic modifications of rice and other food crops."With genetic engineering and even with traditional breeding, it's important that farmers don't become dependent on just a few varieties of a crop, but instead try to preserve diversity," said Jane Rissler, Senior Staff Scientist at the Union of Concerned Scientists in Washington, D.C.. Rissler said "both human health and environmental consequences need to be examined when dealing with any genetic alteration."

Scientists led by Jun Yu, a research scientist at the University of Washington Genome Center and an Associate Director of the Beijing Genomics Institute, studied the indica strain, the most common type of rice grown in China and other Asia-Pacific regions.

Researchers at the Swiss agro-chemical company Syngenta International sequenced the genome of the japonica strain, a subspecies grown in more arid regions. The japonica genome is expected to reveal the gene responsible for Vitamin A production, which could lead to rice with higher vitamin content.

A genome is an organism's genetic material, usually DNA. Genome sequencing means figuring out the order of DNA nucleotide (made up of Adenine (A), Guanine (G), Thymine (T) and Cytosine (C)). The human genome, for example, is made up of more than 3 GBP of these genetic components. While determining this sequence is a vital step, scientists must then figure out how those sequences work together to make an organism develop, maintain itself, and reproduce.

Why Does the Rice Plant Need 50 Thousand Genes?

The rice research reveals that the plant may be more complex than scientists first thought. It's been found that rice is densely populated with many small genes and that the rice plant has about 50,000 genes. {By contrast, it's believed that the human genome has between [35,000 - 40,000] genes.} "Plants do photosynthesis, an extremely complicated process, and without plants, we'd all be dead," Ronald said. [ Editor's Note: I do not believe that the presence of chloroplasts in the leaves of green plants can explain a requirement for so many genes in plants but are not found in animals. We have a little more work to do to find the answer, and we simply don't know yet. We do know that all grain plants, including corn and wheat, have many of the same genes as rice.]

In recent years, scientists have learned that unlocking the genetic code of one organism can quickly lead to a better understanding of other living things. For example, the sequencing of the genes of the fruit fly just two years ago has helped geneticists and physicians understand how genes function in human disease. Likewise, this first complete genome sequencing of a crop plant could provide a model for understanding and improving other grains, including wheat, barley and corn. The United Nations World Food Program reports that 24,000 people die from hunger and hunger related causes each day, and 800 million get inadequate nutrition.