Iron supply prevents Cd uptake in Arabidopsis by inhibiting IRT1 expression and favoring competition between Fe and Cd uptake

Abstract

Cadmium (Cd) is a heavy metal that is highly toxic to organisms. Studies have shown that an increasing Fe supply decreases Cd accumulation in plants. In this study, we investigated the mechanism underlying the effect of Fe on Cd uptake. We compared the effects of Fe application on Cd levels in wild-type Arabidopsis thaliana Col-0 and IRT1-null mutant irt1 (loss in function of Fe2+ uptake). In the Fe-Cd alternative rotation treatment, which ensured asynchronous uptake of Fe2+ and Cd2+, the irt1 mutants had a lower Cd level than the Col-0 plants. In addition, an increase in the Fe supply decreased the Cd level in Col-0 plants, accompanied by an inhibition of IRT1 expression in roots. Furthermore, both Col-0 and irt1 plants grown in Fe-Cd alternative rotation treatment, showed higher Cd uptake than those grown in another rotation treatment, which allowed synchronous uptake of Fe2+ and Cd2+. Nevertheless, the differences in Cd uptake between the two rotation treatments were greater in Col-0 plants than in irt1 mutants. Inhibition of IRT1-mediated Cd uptake and enhancement of antagonism between Fe and Cd uptake are two mechanisms involved in the inhibition of Cd uptake by Fe supply.