Application of oyster shell powder reduces cadmium accumulation by inhibiting the expression of genes responsible for cadmium uptake and translocation in rice

The application of waste oyster shell in agriculture is of extensive concern due to its benefits on improving yields and inhibiting cadmium (Cd) accumulation in edible parts of crops. However, the underlying mechanisms responsible for oyster shell powder (OSP) that decreases Cd accumulation in crops remain poorly understood. This study explored the effects of OSP on growth and Cd accumulation in rice via pot experiments and hydroponics. Pot experiments showed that the application of 1 g·kg−1 OSP improved rice yields and decreased Cd concentrations in all tissues of rice, especially in grains, which was reduced by 43.5%. The pH was increased and the phytoavailability of Cd in soil was reduced by OSP supplementation. In addition, OSP also exhibited high dissolution of Ca, Fe, Zn, and Se. In hydroponics, OSP supply also suppressed Cd accumulation in rice and increased plant growth. Pretreatment with OSP inhibited the accumulation of Cd in the roots and shoots. Simultaneously, OSP reduced the content of Cd in the root cell sap, cell wall, and xylem sap, and downregulated the expression of OsNramp5, OsNramp1, OsIRT1, and OsHMA2. These findings suggested that the application of OSP could reduce Cd accumulation by inhibiting the expression of genes responsible for Cd absorption and xylem loading in rice.