Salicylic Acid Ameliorates Cadmium Toxicity by Increasing Nutrients Uptake and Upregulating Antioxidant Enzyme Activity and Uptake/Transport-Related Genes in Oryza sativa L. indica

Cadmium (Cd) is highly toxic to plants and limits crop growth and productivity; it also affects the uptake and distribution of nutrients, accelerates oxidative damage, and disrupts metabolic pathways in plants. Salicylic acid (SA) is an important stress-signaling molecule that has been reported to ameliorate the deleterious effects of Cd in many plant species. In this study, the ability of 100 mu M SA application to alleviate the effects of 5 mu M Cd stress was investigated in ErJiuNan1 (EJN1, an early-indica rice genotype) under hydroponic culture. The results showed that the addition of SA alleviated Cd toxicity by increasing the accumulation of nutrients (Mn, Fe), increasing the activity of antioxidative defense system (e.g., superoxide dismutase, peroxidase, and soluble protein), and decreasing lipid peroxidation. SA addition in Cd-stressed rice plants upregulated the expression of Cd stress tolerance genes (OsHMA3 and OsNRAMP5), which enhanced Cd tolerance, reduced the accumulation of Cd, and affected Mn accumulation. The expression of Fe-inducible genes (OsIRT1, OsNRAMP1, OsNAS3, and OsYSL15) was upregulated in response to Cd exposure but significantly down-regulated by exogenous SA treatment. Furthermore, co-application of Cd and SA upregulated the expression of the SA biosynthesis-associated genes OsICS1 and OsWRKY6. Thus, SA application might alleviate Cd toxicity by reversing the negative effects of plant growth stemming from Cd exposure and improve Cd tolerance by modulating the expression of uptake/transport-related genes.

Automated summary

Salicylic acid (SA) application can alleviate the toxic effects of cadmium (Cd) on plants by increasing nutrient accumulation, enhancing the activity of antioxidative defense system, and reducing lipid peroxidation. SA application can also improve Cd tolerance by modulating the expression of Cd stress tolerance genes and affecting manganese (Mn) accumulation. Furthermore, SA application can regulate the expression of iron (Fe) related genes to reduce the response to Cd exposure.