Differences and mechanisms of selenocysteine and selenomethionine binding to cadmium in soil and rice grains

Authors: NIU, SHANSJAN - University Of Science And Technology Of China; FAROOQ, MOHAMMED RAZA - University Of Science And Technology Of China; LI, MENGQI - Zhejiang University Of Technology; SONG, JIAPING - Chuzhou University; WANG, ZHANGMIN - Suzhou University Of Science And Technology; DANSO, OFORI PRINCE - University Of Science And Technology Of China; YIN, XUEBIN - Chuzhou University; LIU, XIAODONG - University Of Science And Technology Of China; Banuelos, Gary; ZHANG, ZEZHOU - Chuzhou University

Submitted to: Journal of Food Composition and Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/14/2026
Publication Date: 5/19/2026
Citation: Niu, S., Farooq, M., Li, M., Song, J., Wang, Z., Danso, O., Yin, X., Liu, X., Banuelos, G.S., Zhang, Z. 2026. Differences and mechanisms of selenocysteine and selenomethionine binding to cadmium in soil and rice grains. Journal of Food Composition and Analysis. 155. Article 109248. https://doi.org/10.1016/j.jfca.2026.109248.
DOI: https://doi.org/10.1016/j.jfca.2026.109248

Interpretive Summary: Many types of rocks and soils contain naturally high levels of heavy metals, i.e., cadmium (Cd) and selenium (Se). Depending on the crop, plants can accumulate high concentrations of heavy metals that are not only toxic to the crop but also can be harmful to humans consuming a crop with high concentrations of Cd. In China, black shale and associated soils are known to have levels of naturally occurring Cd and Se. The co-existence of both elements is of great interest because many Se biofortification strategies are being developed in such soils to combat Se deficiencies for over 800 million Chinese. Because of the similarity with sulfur, plants will accumulate Se when grown in soils high in Se. Depending on the crop and the soil, plants will also accumulate Cd in certain parts of the plant. For this reason, it is important to evaluate other heavy metals like Cd when establishing Se biofortification strategies on Chinese soils high in Se. In this study, both Se and Cd accumulation were evaluated in soil and in rice grown for Se biofortification in paddies located in soils high in Se and Cd. Results showed that certain forms of Se in the soil reduced the uptake of Cd and other forms of Se present in the rice binded with Cd that had accumulated in the plant. The binding of Cd with Se within the rice grains may reduce the absorption of Cd by humans. More research is needed, however, to investigate the food safety of consuming rice with Se/Cd complexes when it is grown for Se biofortification in Se-rich shale soils in China.

Technical Abstract: Heavy metals such as cadmium (Cd) are naturally abundant in black shale and sedimentary rocks and often coexist with elements such as selenium (Se) in the weathered soils. The existence of potentially toxic Cd in soil is, however, divided into water-soluble and non-water-soluble Cd. Ionic states such as CdCl2, Cd (NO3)2, CdCO3, and complexed states such as Cd (OH)2 are water-soluble, easy to migrate and can be absorbed by plants, while insoluble Cd compounds such as Cd precipitate, colloidal adsorbed Cd, are not easy to migrate or to be absorbed by plants. Cadmium contamination has become a major public health concern due to its high transfer rate from soil to plants. It has a long half-life (about 10-30 years) in the human body and is a chronic potent nephrotoxin recognized as a Class I human carcinogen by the International Agency for Research on Cancer. Numerous studies have shown that Se has an antagonistic effect on the toxicity of Cd in plants and its accumulation in biological systems. As a result, understanding the interaction mechanism between Se and Cd in soil-crop systems is critical for the safe production of Se-biofortified crops grown in shale soils high in Se and Cd. In this study, levels of Cd and Se and their respective speciation forms were investigated through comparative analyses in soils and rice paddy systems established for Se biofortification in shale soils in China. Results showed different forms of selenoamino acids complexed with Cd in soil and reduced the mobility and upward transport of Cd into the plant, while other Se/Cd complexes were also identified in rice grains. This finding is important because their existence within the rice kernels may result in less Cd absorption by intestinal cells when Se-enriched rice produced in Se-containing shale is consumed by humans. Although Cd absorption may be reduced in humans, future studies are needed, however, to explore the human health safety of consuming rice containing Se/Cd complexes.