Inhibition of Nitrate Transporter 1.1-Controlled Nitrate Uptake Reduces Cadmium Uptake in Arabidopsis

Abstract

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 2 ) uptake in Arabidopsis (Arabidopsis thaliana) and impairs NO 3 2 homeostasis in roots. In NO 3 2-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 2 -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 2 uptake-dependent manner. Furthermore, using a treatment rotation system allowing synchronous uptake of NO 3 2 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 2 and cadmium and asynchronous uptake of nutrient cations. We conclude that, although inhibition of NRT1.1-mediated NO 3 2 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.

A reevaluation of the contribution of NRT1.1 to nitrate uptake in Arabidopsis under low‐nitrate supply

“…A disruption in NRT1.1 affects the expression of other NRT genes [10,24,31,32], which is highly associated with growth conditions. A critical factor in the controversial conclusions described above may be the variable interference resulting from nitrate uptake by other NRTs.…”

Inhibition of DNA demethylation enhances plant tolerance to cadmium toxicity by improving iron nutrition

“…Crops grown in Cd‐contaminated soils are the main route of Cd entry into the human body through the food chain, causing a serious threat to human health (Clemens, Aarts, Thomine, & Verbruggen, ; Wei & Yang, ). Excess Cd accumulation in plants also causes several visible phytotoxic symptoms, including retardation of growth, modification of enzymes, chlorosis of the leaf, oxidative stress, and disturbances in mineral nutrition (Choppala et al, ; Lux, Martinka, Vaculik, & White, ; Mao et al, ). To cope with these adverse effects, plants have evolved a host of protective mechanisms to minimize Cd toxicity, such as prevention of Cd entry into the roots, compartmentalization of Cd in vacuoles, Cd chelation by phytochelatins and metallothioneins, and immobilization of Cd in the cell wall (Choppala et al, ; Clemens et al, ; Guan, Zhang, Pan, Jin, & Lin, ; Lux et al, ).…”

Increased Sucrose Accumulation Regulates Iron-Deficiency Responses by Promoting Auxin Signaling in Arabidopsis Plants

“…Histochemical assay of GUS gene expression in roots of DR5::GUS transgenic plants was performed as described in our previous study (Mao et al, 2014), and the distribution and intensity of the blue product observed under a microscope (Nikon Eclipse E600, Nikon).…”