Exploring the mechanism of Cd uptake and translocation in rice: Future perspectives of rice safety

Cadmium (Cd) contamination in rice fields has been recognized as a severe global agro–environmental issue. To reach the goal of controlling Cd risk, we must pay more attention and obtain an in–depth understanding of the environmental behavior, uptake and translocation of Cd in soil–rice systems. However, to date, these aspects still lack sufficient exploration and summary. Here, we critically reviewed (i) the processes and transfer proteins of Cd uptake/transport in the soil–rice system, (ii) a series of soil and other environmental factors affecting the bioavailability of Cd in paddies, and (iii) the latest advances in regard to remediation strategies while producing rice. We propose that the correlation between the bioavailability of Cd and environmental factors must be further explored to develop low Cd accumulation and efficient remediation strategies in the future. Second, the mechanism of Cd uptake in rice mediated by elevated CO2 also needs to be given more attention. Meanwhile, more scientific planting methods (direct seeding and intercropping) and suitable rice with low Cd accumulation are important measures to ensure the safety of rice consumption. In addition, the relevant Cd efflux transporters in rice have yet to be revealed, which will promote molecular breeding techniques to address the current Cd–contaminated soil–rice system. The potential for efficient, durable, and low–cost soil remediation technologies and foliar amendments to limit Cd uptake by rice needs to be examined in the future. Conventional breeding procedures combined with molecular marker techniques for screening rice varieties with low Cd accumulation could be a more practical approach to select for desirable agronomic traits with low risk.