Metabolic adaptations of rice roots to methylmercury: Insights from high and low accumulators

The consumption of rice enriched with methylmercury (MeHg) is one of the important exposure routes, posing threats to human health. However, metabolic responses of different rice varieties to soil MeHg remain unclear. Here, we analyzed the changes in root metabolites of high- (H699) and low-accumulating (H777) rice varieties under MeHg stress via untargeted metabolomics. MeHg (0.9 μg g^-1) led to a significant increase in oxidative damage and antioxidant enzyme activities in leaves, suggesting leaves are more sensitive to MeHg. Distinct metabolite profiles occurred in rice roots under MeHg stress, with H699 predominantly involving lipid metabolism pathways, whereas H777 engaged amino acid metabolism pathways. Two key metabolites, silymarin and 12-hydroxylauric acid can effectively alleviate MeHg stress in rice by reducing MeHg accumulated in rice roots by ∼85 %. Overall, this study provides key targets and foundations for breeding low-MeHg, tolerant rice, crucial for reducing grain MeHg, ensuring safety, and protecting health.