Elucidating mechanisms that differentiate between uptake of toxic heavy metals and beneficial micronutrients in food crops

PROJECT SUMMARY Cadmium (Cd) is an important contaminant that threatens human health, as well as agricultural productivity and biodiversity. In the United States, the largest source of Cd exposure in non-smoking adults and children is through the diet. Although adverse effects on kidneys, bones and as a carcinogen are well documented, there

is emerging evidence that Cd has significant neurotoxicological effects at low doses especially in pediatric population. Several studies have found most grain containing baby foods have an abundance of cadmium. Although decreasing cadmium in grains will lower dietary exposure the problem is exacerbated by attempts to increase

iron and zinc micronutrients. Efforts aimed to address population-level micronutrient deficiency inadvertently cause elevated toxic metals such as cadmium. A simple solution to avoid metal toxicity is to breed plants with selective uptake of beneficial micronutrients without the concomitant uptake of toxic heavy metals. Since little

is known about the grain loading processes of cadmium, it is imperative to understand the dynamics of cadmium movement to grains, and how cadmium uptake interacts or interferes with zinc distribution within plants. Dietary exposure to cadmium depends not only on the concentration of cadmium in the food but also on

the bioavailable fraction of cadmium from the food. Previous studies have only examined bioavailability of cadmium in foods, without assessing how micronutrients affect cadmium bioavailability. Therefore, our long- term goal is to achieve biofortification of essential micronutrients such as zinc without the commensurate

increase in the concentration of contaminants such as cadmium. Our overall goal for this study is to determine how zinc alters cadmium transport, accumulation and bioavailability in wheat. The specific aims proposed to attain our overall goal are 1) To define translocation and accumulation of cadmium from root to shoot to seed

in wheat and 2) To determine the mechanism by which addition of zinc to the soil alters cadmium bioavailability. We will determine the relationship between cadmium accumulation and bioaccessibility in response to zinc treatment, for which data do not exist. This new knowledge will include genes that can be

studied in greater detail to characterize the localization and complexation of cadmium and zinc in the grains. The proposed research will have a strong positive impact because we will generate knowledge needed to enhance the nutritional quality of major cereal crops while limiting bioavailability of toxic metals

such as cadmium that threatens human health especially children.