Calcium and Selenium Synergistically Decrease Cadmium Content in Pepper (Capsicum annuum L.) by Modulating Key Genes Involved in Cadmium Absorption and Translocation

Calcium (Ca) and selenium (Se) are garnering growing interest because of their capacity to boost crop yields and minimize cadmium (Cd) concentration within edible parts. However, whether Ca and Se can synergistically inhibit Cd accumulation in crops and its mechanism remains poorly understood. A hydroponic experiment was conducted under Cd exposure with the combined supplementation of Ca and Se, specifically focused on Cd accumulation and its mechanism. The results revealed that Ca and Se synergistically enhanced growth and photosynthetic content, whereas they inhibited Cd accumulation in the roots, stems, and leaves of peppers. Ca and Se also synergistically reduced the content of Cd in the cell wall, organelle fraction, and soluble fraction of the roots, as well as in pectin, hemicellulose I, hemicellulose II, and cellulose. Ca and Se supplementation synergistically downregulated the expression levels of CaNramp1, CaNramp5, CaHMA1, and CaHMA2. These results revealed that Ca and Se synergistically reduced Cd accumulation in peppers by modulating targeted gene downregulation involved in Cd absorption and translocation.