Suicidal Plant Gives Researchers Insights on Iron

Diggle, a mutant pea plant with a suicidal love for iron, may someday offer scientists a biotechnology approach for reducing anemia.

Anemia, or iron-poor blood, affects 2 billion people--about one-third of the world’s population, according to World Health Organization statistics. Inadequate iron in the diet is the leading cause.

Plant physiologist Michael Grusak at the Agricultural Research Service would like to understand and modify Diggle’s “stupid plant trick.” ARS is the USDA's chief scientific agency.

Grusak's major aim: improve the iron content of staple crops such as rice. This would especially benefit people in developing countries, who mostly eat vegetarian diets. Only 5 percent of the iron in plants is bioavailable--usable by the body as a nutrient. By contrast, 30 to 50 percent of iron in meat is usable.

Plants hoard iron, using a protein, ferritin, to store it in seeds and leaves. But ferritin also binds iron, making it hard for the body to use.

Rice has only 6 parts per million iron after milling. Most pea seeds have 60 ppm, so that, pound for pound, peas’ 5 percent of bioavailable iron yields more of the nutrient than rice. Diggle peas have a whopping 250 to 280 ppm iron. The plant ships so much of this essential mineral to leaves and seeds that it eventually poisons itself.

All plants move iron to seeds with a special biochemical. Grusak’s hypothesis is that Diggle employs a different transport chemical.

If Diggle’s trait is genetic and transferable to other crops, the idea would be to turn it “on” when a crop is making seeds, but keep it “off” at other times so the plant doesn’t overdose on the nutrient.

Diggle’s name comes from its genetic classification, "dgl," scientific shorthand for "degenerative leaves." The leaves are marked by numerous tiny dark spots.

Scientific contact: Michael A. Grusak, ARS Children’s Nutrition Research Center at Baylor College of Medicine, 1100 Bates Street, Houston, TX 77030-2600, phone (713) 798-7044, fax (713) 798-7078, mgrusak@bcm.tmc.edu.