Plant cadmium resistance 2.7 from Brassica napus (BnPCR2.7) improves copper and cadmium tolerance

Abstract

Copper (Cu) and cadmium (Cd) are highly phytotoxic heavy metals that are widespread contaminants in soil. Plants are efficient at taking up heavy metals, which adversely impacts human health. Therefore, it is important to decrease the accumulation of Cu/Cd in plants to reduce human exposure from the food web. Here, we determined the function of a rapeseed (Brassica napus) Cu/Cd transporter, plant cadmium resistance protein 2.7 (BnPCR2.7), in enhancing Cu/Cd tolerance in seedlings and decreasing the accumulation of Cu/Cd in seeds. A subcellular localization analysis revealed that BnPCR2.7 is localized at the plasma membrane (PM). CRISPR/Cas9-mediated BnPCR2.7 knockout lines and knockdown lines had increased sensitivity to high Cu/Cd than wild-type (WT) plants. In contrast, overexpression of BnPCR2.7 enhanced the adaptation to high Cu/Cd than in WT. Additionally, the Cu/Cd content in the roots of overexpression lines was significantly lower than those of the WT, while the contents in the stems increased. A non-invasive micro-test technology (NMT) assay showed that overexpression plants promoted the efflux of Cu and Cd from the roots. A field trial of rapeseed grown in soil contaminated with Cu or Cd showed that overexpression plants grew and developed better than the WT with higher yields and less Cu/Cd that accumulated in the seeds, while knockout and knockdown lines were contrary to these results. Additionally, when grown in soils contaminated by both Cu and Cd, the content of these heavy metals decreased by 12–20 % and 20–30 %, respectively, in seeds of overexpression lines. Collectively, BnPCR2.7 may promotes resistance to Cu/Cd by efflux pathways. Significantly, it is a candidate genetic resource to increase the resistance to heavy metals and reduce the accumulation of Cu/Cd in rapeseed.