Golden Rice Is Life

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November, 2000: Indonesia

 

Rice chow line at a wedding reception in Banaue, Ifugao, Philippines, on 22 April 2000. (Photo courtesy of the International Rice Research Institute [IRRI].)

World areas of blindness caused by VAD.

Oryza sativa.

Inserting foreign genes by using the Agrobacterium Ti plasmid

The parts of a rice grain.

Mini flood plain with Oryza on display at the Missouri Botanical Garden. Note that the lowland plant grows with its root submerged in water. The evolution of these submerged roots allows for the extraction of needed nutrients directly from the water (hydroponics). (© 1999 Erica Kipp.)

 

Three of the world's four most populous nations are rice-based societies–China, India, and Indonesia. Together, their nearly 2.5 billion people each consume about 175 kilograms of rice annually. This means that over 50% of the world's people depend on rice for about 80% of their calorie requirements. Besides cooked rice, breakfast cereals, desserts, rice cakes, and rice flour, rice is used in beer and in a Japanese rice-wine called "sake." But although rice provides a lot of nutrition, the edible portion is deficient in vitamin A. Thus, much of the rice-dependent/rice-producing area falls victim to xerophthalmia, a progressive disease of the eye directly linked to vitamin A deficiency (VAD). Now, to remedy this situation, scientists and collaborators have developed a genetically modified rice grain that is able to produce carotenoids, the precursors to vitamin A production in humans.

According to the International Eye Foundation (IEF), 70% of childhood blindness is caused by xerophthalmia. Although the IEF has attempted to reduce vitamin A deficiency by supplying vitamin A capsules, sugar fortified with vitamin A, and nutritional education, many people have not been reached, and xerophthalmia remains the leading cause of blindness in the developing world. In addition to diseases of the eye, VAD increases a person's susceptibility to infection. Although VAD is largely preventable, the World Health Organization estimates that an additional 230 million children are at risk of VAD annually.

The carotenoids the human body needs to produce vitamin A are found only in the green parts of the rice plant. Since people consume the rice grain itself, it stands to reason that VAD is concentrated in areas where rice is the major staple and source of calories. Carotenoids are red, orange, or yellow lipid-soluble pigments found in all chloroplasts and in cyanobacteria. They are embedded within the thylakoid membranes where they function, along with chlorophyll b, to broaden the spectrum of light available for photosynthesis. Known as accessory pigments, they transfer the light energy they absorb to molecules of chlorophyll a. The two groups of carotenoids are carotenes (including beta-carotene) and xanthophylls. While normally present in chloroplasts, they are often masked by the chlorophylls, visible only when the chlorophylls break down in deciduous leaves in autumn.

Of the 20 known species of rice (and more than 90,000 varieties), the two cultivars are Asian rice (Oryza sativa) and African rice (Oryza glaberrima). Now, through gene-splicing techniques, Oryza has been genetically modified to produce carotenoids. The carotenoid production was achieved by adding two genes from the daffodil, Narcissus spp., and one gene from the bacterium Erwina uredovora. The resulting grain has been dubbed "golden rice" because it has a yellow-orange endosperm. (Narcissus is in the Liliaceae family of monocots. Their petals are united in a corolla tube and are often bee- or butterfly-pollinated. Erwina is a member of the Monera kingdom of prokaryotic cells.)

The principal investigators for the genetically modified (GM) rice grain are Dr. Ingo Potrykus of the Swiss Federal Institute of Technology's Institute for Plant Sciences and Dr. Peter Beyer of the Center for Applied Biosciences, University of Freiburg, Germany. Funding for the development of the GM rice grain over the past 10 years has been provided by several sources, including the Rockefeller Foundation, the Swiss Federal Institute of Technology, and Greenovation, a plant biotechnology company. Zeneca Agrochemicals, involved with funding the GM rice project since 1996, has commercial rights. Collaborators anticipate availability for golden rice planting and harvesting sometime in 2003.

Even though rice is grown in more than 100 countries, it is most productive in humid, tropical regions. The lowland rice we are most familiar with requires 5,000 liters of water to produce 1 kilogram of rice, and thus is typically grown in flood plain areas known as paddies. (Less productive upland rice is grown in regions of low rainfall.) Oryza is a genus in the grass or Poaceae family, a family of monocots. The endosperm is that portion containing the starch; this stored polysaccharide is the energy source to be converted by the germinating seed. The endosperm is surrounded by the bran, tissue where the bulk of proteins, B vitamins (such as thiamin, niacin, and riboflavin), minerals (such as iron, potassium, and phosphorus), and oils are found. During processing, the outer protective covering, the rice hull, is removed since the bran and endosperm are the only edible portions of the grain. The bran and endosperm together are known as brown rice. White rice has had the bran removed; thus, it is less nutritious than brown rice and is often fortified after bran removal. However, white rice cooks faster and has a longer shelf life, so bran removal and subsequent fortification is sometimes preferred, especially in areas where long-term or cold storage is not an option.

Rice has nonfood uses as well. The inedible rice hull is used as fuel, fertilizer, packing material, and insulation. The bran is used in cooking oil, soap and cosmetics, and as a food additive that provides fiber and increased nutritional content. Straw from the leaves and stems is also economically valuable. It is woven into roofs, hats, baskets, mats, and sandals; twisted into sticks for fuel; made into paper; and used as bedding and fodder for cattle.

References, Websites, and Further Reading

Simpson, B.B., and Molly C. Ogorzaly. 1995. Economic botany: Plants in our world. 2d ed. New York: McGraw-Hill Publishing Company, pp. 179—83.

White, Peter T. 1994. Rice: The essential harvest. National Geographic, May, pp. 48—79.

http://www.asiarice.org/ The Asian Rice Foundation

http://www.riceweb.org/ Rice Web, a compendium of facts and figures from the world of rice

http://www.cgiar.org/irri/ International Rice Research Institute (IRRI), established to help farmers in developing countries grow more rice on limited land with less water, less labor, and fewer chemical inputs, and to do so without harming the environment.

http://www.iefusa.org/ International Eye Foundation

http://encarta.msn.com "Rice," Microsoft® Encarta® Online Encyclopedia 2000. © 1997—2000 Microsoft Corporation. All rights reserved.

Stern, Introductory Plant Biology, 8th Edition

Chapter 1: What Is Plant Biology?
The relationship of humans to their environment, pp. 4—6

Chapter 2: The Nature of Life
Carbohydrates, pp. 22—23
Lipids, p. 23

Chapter 3: Cells
Plastids, p. 37

Chapter 7: Leaves
Autumnal changes in leaf color, pp. 120—21

Chapter 8: Flowers, Fruits, and Seeds
Structure of flowers, pp. 129—32
Seeds and germination, pp. 143—47
Monocot structure and germination, fig. 8.29, p. 144

Chapter 10: Plant Metabolism
Chlorophyll, pp. 169—70
Absorption spectrum of chlorophyll a, chlorophyll b, and a carotenoid, fig. 10.7, p. 172

Chapter 11: Growth
Vitamins, p. 188

Chapter 17: Kingdom Monera and Viruses
Kingdom Monera, pp. 280—92
Cyanobacteria, pp. 292—95

Chapter 23: Flowering Plants
Pollination, p. 421
Pollination ecology, pp. 425—30

Chapter 24: Flowering Plants and Civilization
Poaceae, p. 454
Liliaceae, p. 454—56

Chapter 26: Biomes
Tropical rain forest, pp. 487—88

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