Alleviation of cadmium toxicity and minimizing its accumulation in rice plants by methyl jasmonate: performance and mechanisms.

Abstract

Heavy metal pollution is a worldwide problem that threaten agricultural production and human health. Methyl jasmonate (MeJA) is a phytohormone that could enhance plant resistance against various stresses. However, the mechanism of MeJA in cadmium (Cd) uptake, distribution, and translocation in rice plants remains elusive. In this study, we found that the Cd induced-growth inhibition was ameliorated by MeJA. Upon MeJA application, Cd content in root and shoot was decreased by 10.15% and 36.39%, which paralleled with less Cd²⁺ influx of rice roots and depressed expression of the cation transporters (OsNramp1 and OsNramp5). The subcellular distribution revealed that MeJA enriched Cd distribution in cell wall, which was accompanied by increased cell wall thickness and altered cell wall polysaccharide (pectin, cellulose, hemicellulose) content, meanwhile, the Cd content in pectin, cellulose, hemicellulose was increased, the FTIR analysis implied that functional groups (especially -OH and COO-) on cell wall were involved in Cd fixation. The root to shoot translocation of Cd was hindered by exogenous MeJA, this was validated by the decreased expression of OsHMA2 in root and declined Cd level in xylem sap. Overall, our results revealed that MeJA could act as a foliar resistance control substance to reduce Cd accumulation in rice plants. The detailed molecular mechanisms of MeJA in Cd detoxification in plants still need further investigation.