Hydrogen peroxide mediates cadmium accumulation in the root of a high cadmium-accumulating rice (Oryza sativa L.) line

Hydrogen peroxide (H 2 O 2 ) is a vital signaling molecule in response to cadmium (Cd) stress in plants. However, the role of H 2 O 2 on Cd accumulation in root of different Cd-accumulating rice lines remains unclear. Exogenous H 2 O 2 and 4-hydroxy-TEMPO (H 2 O 2 scavenger) were applied to investigate the physiological and molecular mechanisms of H 2 O 2 on Cd accumulation in the root of a high Cd-accumulating rice line Lu527–8 through hydroponic experiments. Interestingly, it was found Cd concentration in the root of Lu527–8 increased significantly when exposed to exogenous H 2 O 2 , while reduced significantly when exposed to 4-hydroxy-TEMPO under Cd stress, proving the role of H 2 O 2 in regulating Cd accumulation in Lu527–8. Lu527–8 showed more Cd and H 2 O 2 accumulation in the roots, along with more Cd accumulation in cell wall and soluble fraction, than the normal rice line Lu527–4. In particular, more pectin accumulation, especially low demethylated pectin, was observed in the root of Lu527–8 when exposed to exogenous H 2 O 2 under Cd stress, resulting in more negative functional groups with greater capacity to binding Cd in the root cell wall of Lu527–8. It indicated that H 2 O 2 -induced cell wall modification and vacuolar compartmentalization contributes greatly to more Cd accumulation in the root of the high Cd-accumulating rice line.