Glutathione is involved in selenium detoxification and suppresses the selenate-induced SULTR1:1 gene expression in plants

Authors: CARDOSO, ARNON - Federal University Of Lavras; NAMAORATO, FILIPE - Federal University Of Lavras; GUILHERME, LUIZ - Federal University Of Lavras; SILVA, MARIA - Federal University Of Lavras; Liu, Jiping; Li, Li

Submitted to: Environmental and Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2023
Publication Date: 6/26/2023
Citation: Cardoso, A., Namaorato, F., Guilherme, L., Silva, M., Liu, J., Li, L. 2023. Glutathione is involved in selenium detoxification and suppresses the selenate-induced SULTR1:1 gene expression in plants. Environmental and Experimental Botany. http://dx.doi.org/10.2139/ssrn.4427870.
DOI: https://doi.org/10.2139/ssrn.4427870

Interpretive Summary: Selenium (Se) is an essential nutrient for humans and a beneficial element for plants. However, excess Se is toxic to plants. In this study, by using Arabidopsis glutathione (GSH)-deficient mutant pad2-1 as well as with treating plants with GSH and GSH synthesis inhibitor, we provide direct evidence showing that GSH is involved in Se detoxification. Furthermore, we show that the selenate-induced SULTR1;1 gene expression is negatively regulated by the cellular GSH content. In addition, selenate confers higher toxicity than selenite under low sulfur conditions in plants. Sulfur alleviated selenate toxicity, which is associated with GSH levels. Our findings demonstrate the critical role of GSH in resistance to Se toxicity and provide insights into processes related to Se toxicity in plants, which enhances our understanding of metal tolerance for Se biofortification in crops.

Technical Abstract: Selenium (Se) as a sulfur (S) analog is beneficial to plants. However, excessive Se is toxic. Glutathione (GSH) can protect plant cells from metal toxicity. In this study, we investigated the roles of GSH in resistance to Se toxicity and in regulating transporter gene expression. We also examined the effects of Se and S treatments on GSH production and growth of Arabidopsis thaliana (a non-Se-accumulator) and broccoli (Brassica oleracea var. italica, a secondary-Se-accumulator) plants. By treating the Arabidopsis wild-type and the glutathione-deficient mutant pad2-1 plants with and without selenate, reduced glutathione or GSH synthesis inhibitor buthionine sulfoximine, we showed that glutathione is involved in selenium detoxification. The pad2-1 mutant exhibited lower selenate tolerance, and GSH supply alleviated the toxicity. However, selenate treatment reduced GSH levels in a dose-dependent manner, which was further augmented in low S conditions. Interestingly, the selenate-induced SULTR1;1 gene expression was negatively associated with GSH levels in plants. The pad2-1 mutant showed much higher AtSULTR1:1 expression than WT under excess Se supply, and GSH supply partially inhibited its expression. Moreover, selenate conferred higher toxicity than selenite under a low S supply in broccoli plants. In contrast, S alleviated selenate toxicity, which was associated with GSH levels. These findings demonstrate the critical role of GSH in resistance to Se toxicity and provide insights into processes related to Se resistance in plants, which enhances our understanding of metal tolerance for Se biofortification in crops.