| ||
| Vol. 21, No. 5 |
| March 15, 1999 |
|
USDA Researcher Studying Iron-Packed Pea Plants by KRISTINA VAN ARSDEL Texas Medical Center News
Nine years ago, Dr. Michael Grusak came to the Children's Nutrition Research Center (CNRC) looking for a way to combine his background in plant biology and his interest in iron nutrition. What resulted is a research effort that could one day have a major impact on the estimated 2 billion people at risk for iron-deficiency anemia worldwide. "Iron deficiency in humans is a tremendously serious nutritional disorder," says Dr. Grusak, a plant physiologist with the United States Department of Agriculture (USDA). "With 6 billion people estimated in the world, that's a third of the world's population at risk. The reason is that much of the world has a vegetarian-based diet and plant foods typically have a very low iron content in them." Dr. Grusak says it was random luck when he came across two pea plants that had a unique mutation which causes them to over-accumulate iron. Since joining the CNRC, he has used these plants as a model for his research, observing how the pea mutants take in iron and distribute the mineral to their various parts. It may be difficult to notice from a trip through the produce section of a grocery store, but not all peas are created equal. Some have a higher nutritional content; the same is true among other vegetables as well. For example, Dr. Grusak is studying a rice variety from China called Dragon Eyeball, named for its red-hued grains, that contains twice the iron content of a normal rice variety. Dr. Grusak hopes that, in the future, the information he has found working with the pea mutants can be used in other plants, especially rice, which is the number one staple food crop in the world.
"If we could increase the iron content of rice, we could have a significant impact on the world's health with respect to iron nutrition," he says. "At this point, we've characterized the process in pea. We've demonstrated that there is a protein which carries the iron from the leaves into the seeds." A plant's nutrients are transported through two pathways - the phloem and the xylem. The xylem pathway travels up from the roots, carrying water and minerals to the leaves; the phloem pathway brings sugars, amino acids and some minerals from the leaves back down to the roots or out to developing seeds or fruits on the plant. While other scientists in the field have concentrated on the roots as the source for bringing iron into the plant, Dr. Grusak has used his background in phloem transport to study what happens to the iron once it is absorbed. He is particularly interested in directing iron to the seeds of a plant, and one of the pea mutants happens to have the ability to send excess iron to its seeds. "We've learned that it's not just about getting more iron into the plant, but distributing it properly to the edible portions of the plant," he says. Because of their mutation, these plants have the potential to increase their iron content by 100 times the normal amount. Iron can be toxic at such high levels. In order to keep the plants healthy, Dr. Grusak grows them in hydroponics, a liquid nutrient solution, so he can monitor the iron levels. "In most plants, there is a rate limitation on how much iron can be transported from the leaves to the seeds," he says. "In this one mutant we have, we've been able to increase the iron content four fold." Now, he must pinpoint the gene responsible for making the protein that carries iron from the leaves to the seeds. With this information, he hopes to tackle the low iron content in rice. Unlike the pea plants, rice already contains a large amount of iron; however, only 4 percent of it is in the seeds. "For pea, not only do we have to modify the transport process, but we've got to get more iron into the plant," says Dr. Grusak. "In the rice plants we've looked at, we've only seen 4 percent of the iron in the seeds at full maturity. So there is a tremendous reservoir there within the plant." Don't rush to the produce section just yet. Dr. Grusak says the process from greenhouse to grocery store may take about eight to 10 years. "Every part of the world that grows rice has different varieties, different climatic conditions," he says. Once research is successful in rice, the trait will go into state and federally organized breeding programs where a series of factors including growth conditions and yield parameters are considered.
©2006 Texas Medical Center E-Mail: tmc-info@tmc.edu URL: http://www.tmc.edu/tmcnews/03_15_99/page_03.html |
