Lanthanum reduces the cadmium accumulation by suppressing expression of transporter genes involved in cadmium uptake and translocation in wheat

Background and aims Lanthanum (La) is attracting increasing attention due to its effects in enhancing yields and reducing cadmium (Cd) accumulation in crops. Although a few transporter genes are reportedly involved in regulating the Cd accumulation in plants, the mechanisms of La-decreased Cd accumulation in plants remain poorly understood. Therefore, this study aimed to 1) investigate the effects of La on Cd accumulation and growth of wheat and 2) determine whether La regulates the Cd accumulation in wheat correlating with the expression of TaNramp5, TaHMA2 and TaHMA3. Methods Hydroponics and pot experiments were conducted under Cd stressed conditions in the presence or absence of La, with special emphasis on the accumulation of Cd, the expression of TaNramp5, TaHMA2 and TaHMA3, and the growth of wheat. Results La supplementation decreased Cd accumulation in wheat, which resulted in better plant growth. Pre-treatment with La also decreased Cd accumulation in both roots and shoots. La supply resulted in a decreased Cd concentration in the root cell sap, cell wall and xylem sap, respectively. Furthermore, in the pot experiment, La application also reduced Cd accumulation in all tissues of wheat under Cd exposure, and the concentration of Cd in grains decreased by 35.0%. The expression levels of TaNramp5 and TaHMA2 were down-regulated by La supplementation. Conclusions La could efficiently limit Cd accumulation in wheat. The La-decreased Cd accumulation in wheat is probably a consequence of both decreased Cd uptake due to the down-regulation of TaNramp5, and reduced root-to-shoot by the down-regulation of TaHMA2.