Abstract
Selenate, the most common form of selenium (Se) in soil environments, is beneficial for higher plants. Selenate is similar to sulfate in terms of the structure and the manner of assimilation by plants, which involves the reduction of selenate to selenide and the replacement of an S moiety in the organic compounds such as amino acids. The nonspecific incorporation of seleno-amino acids into proteins induce Se toxicity in plants. Selenate alters the plant metabolism, particularly the S metabolism, which is comparable to the responses to S deficiency (-S). However, previous analyses involved high concentrations of selenate, and the effects of lower selenate doses have not been elucidated. In this study, we analyzed the metabolic changes induced by selenate treatment through a non-targeted metabolome analysis and found that 2 µM of selenate decreased the S assimilates and amino acids, and increased the flavonoids, while the glutathione levels were maintained. The results suggest that the decrease in amino acid levels, which is not detected under -S, along with the disruptions in S assimilation, amino acid biosynthesis pathways, and the energy metabolism, present the primary metabolic influences of selenate. These results suggest that selenate targets the energy metabolism and S assimilation first, and induces oxidative stress mitigation, represented by flavonoid accumulation, as a key adaptive response, providing a novel, possible mechanism in plant stress adaptation.