Inhibition of Nitrate Transporter 1.1-Controlled Nitrate Uptake Reduces Cadmium Uptake in Arabidopsis1[C][W]

Cadmium inhibits controlled nitrate uptake by roots, but this has the beneficial effect of reducing cadmium entry into roots . Identification of mechanisms that decrease cadmium accumulation in plants is a prerequisite for minimizing dietary uptake of cadmium from contaminated crops. Here, we show that cadmium inhibits nitrate transporter 1.1 (NRT1.1)-mediated nitrate (NO 3 − ) uptake in Arabidopsis ( Arabidopsis thaliana ) and impairs NO 3 − homeostasis in roots. In NO 3 − -containing medium, loss of NRT1.1 function in nrt1.1 mutants leads to decreased levels of cadmium and several other metals in both roots and shoots and results in better biomass production in the presence of cadmium, whereas in NO 3 − -free medium, no difference is seen between nrt1.1 mutants and wild-type plants. These results suggest that inhibition of NRT1.1 activity reduces cadmium uptake, thus enhancing cadmium tolerance in an NO 3 − uptake-dependent manner. Furthermore, using a treatment rotation system allowing synchronous uptake of NO 3 − and nutrient cations and asynchronous uptake of cadmium, the nrt1.1 mutants had similar cadmium levels to wild-type plants but lower levels of nutrient metals, whereas the opposite effect was seen using treatment rotation allowing synchronous uptake of NO 3 − and cadmium and asynchronous uptake of nutrient cations. We conclude that, although inhibition of NRT1.1-mediated NO 3 − uptake by cadmium might have negative effects on nitrogen nutrition in plants, it has a positive effect on cadmium detoxification by reducing cadmium entry into roots. NRT1.1 may regulate the uptake of cadmium and other cations by a common mechanism.