Suicidal Plant Gives Researchers Insights on
By Jill Lee
December 23, 1998
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
worlds 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 Diggles 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
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. Grusaks
hypothesis is that Diggle employs a different transport chemical.
If Diggles 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 doesnt overdose on the
Diggles 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 Childrens Nutrition Research
Center at Baylor College of Medicine,
1100 Bates Street, Houston, TX 77030-2600, phone (713) 798-7044, fax (713)