Salylic acid minimize cadmium accumulation in rice through regulating the fixation capacity of the cell wall to cadmium

Exogenous salicylic acid reduces cadmium content in spinach (Spinacia oleracea L.) shoots under cadmium stress

BACKGROUND

Consumption of leafy vegetables is a primary route of cadmium (Cd) exposure in the human body. Salicylic acid (SA) is a major stress signaling molecule that alleviates Cd toxicity in various plants. Our study aimed to investigate the effects of different SA concentrations on spinach growth, cadmium accumulation, and stress resistance physiology under cadmium stress (50 µmol/L).

RESULTS

Cd stress significantly markedly decreased spinach growth and biomass, reduced its photosynthetic efficiency, increased activities of antioxidative enzymes, and upregulated the relative expression of several genes involved in cadmium absorption and transport compared to the control. The exogenous application of SA mitigated the harmful effects of Cd in spinach. 0.8 and 1.6 mmol/L SA significantly increased spinach root length, plant height, and biomass and decreased the Cd content in shoots by 30.03 and 17.35% compared to the Cd-treated group. Moreover, SA alleviated the yellowing of leaves caused by Cd stress. Exogenous SA ameliorated Cd toxicity in spinach by reducing reactive oxygen species, malondialdehyde, proline, and soluble protein levels. Exogenous SA application reduced Cd absorption in spinach leaves by downregulating the expression of genes involved in Cd transport, such as SoHMA4-like, SoNramp3.1-like, SoNramp6-like, and SoNramp7.2-like. Principal component analysis and correlation analysis showed that exogenous SA application under Cd stress was correlated with plant Cd content, photosynthetic pigment content, and relative expression of Cd absorption and transportation-related genes.

CONCLUSIONS

To summarize, these findings indicate that SA mitigates Cd toxicity in spinach by reversing the adverse effects of Cd stress on plant growth and reducing Cd accumulation in the shoots.

Brassinosteroid decreases cadmium accumulation via regulating gibberellic acid accumulation and Cd fixation capacity of root cell wall in rice (Oryza sativa)

The precise mechanism behind the association between plants' reactions to cadmium (Cd) stress and brassinosteroid (BR) remains unclear. In the current investigation, Cd stress quickly increased the endogenous BR concentration in the rice roots. Exogenous BR also increased the hemicellulose level in the root cell wall, which in turn increased its capacity to bind Cd. Simultaneously, the transcription level of genes responsible for root Cd absorption was decreased, including Natural Resistance-Associated Macrophage Protein 1/5 (OsNRAMP1/5) and a major facilitator superfamily gene called OsCd1. Ultimately, the increased expression of Heavy Metal ATPase 3 (OsHMA3) and the decreased expression of OsHMA2, which was in charge of separating Cd into vacuoles and translocating Cd to the shoots, respectively, led to a decrease in the amount of Cd that accumulated in the rice shoots. In contrast, transgenic rice lines overexpressing OsGSK2 (a negative regulator in BR signaling) accumulated more Cd, while OsGSK2 RNA interference (RNAi) rice line accumulated less Cd. Furthermore, BR increased endogenous Gibberellic acid (GA) level, and applying GA could replicate its alleviative effect. Taken together, BR decreased Cd accumulation in rice by mediating the cell wall's fixation capacity to Cd, which might relied on the buildup of the GA.