Iron deficiency is one of the most widespread mineral deficiencies, with an estimated 2 million people affected worldwide. Lack of iron in a diet is a major risk factor for disease and death, especially in the developing world.
Food industry applies a variety of methods to increase bioavailable iron in common foods, such as grains. Fortification of processed foods (e.g. production of iron-rich cereal) is one of the main ways to introduce recommended amounts of essential minerals to the regular diet.
However, industrial food fortification is time-consuming and costly, and fortified products often exceed the purchasing power of individuals facing difficult living conditions. Not incidentally, these people are at the greatest risk of nutrient deficiency related disease.
Genetic engineering of common crops, such as rice, may become a powerful and sustainable tool in food industry. Biofortification – boosting the nutritious value “from within” – could significantly increase the amount of iron in edible portions of plants, a quality which would be inherited generation after generation.
Rice in general is a compelling target for biofortification, since it is often the main dietary grain in developing countries, where iron deficiency anemia is prominent. Brown rice is, in fact, relatively rich in micronutrients; however, polished white rice, which is the main form it is consumed in, contains only the endosperm tissue with low amounts of iron and does not meet the dietary requirements without supplementation.
One of the more straight-forward methods for creating transgenic fortified rice is the upregulation of iron storage proteins, such as ferritin. Ferritin has been demonstrated to be a potent iron storage agent within the cell. Moreover, ferritin-stored iron is readily absorbed by human gastrointestinal tract. For example, soybeans are rich in ferritin and therefore are an excellent source of iron.
Soybean ferritin gene can be activated under the control of endosperm-specific promoters in rice; therefore, only the endosperm tissue is enriched in iron. As such, the amount of bioavailable iron in white rice has been demonstrated to increase significantly, especially in cases where ferritin upregulation was supplemented with genetic enhancement of iron uptake from the soil, and translocation to the seeds, which is otherwise somewhat deficient in rice.
Even though biofortification could generally be achieved by artificial selection of lines relatively rich in iron, transgenic supplementation of these varieties is, without a doubt, superior to conventional breeding. Novel genetic engineering approaches still need to be developed to reach recommended micronutrient levels in rice, however biofortification is already becoming a powerful tool in solving global iron deficiency anemia.