An atlas of plant selenium metabolism

Selenium (Se) is not only a rare and toxic element but also an essential micronutrient for humans and animals that is often in short supply. Terrestrial plants do not require Se, but it can have growth-promoting or negative effects, depending on the exposure level. In this Tansley review, we draw up a comprehensive metabolic map of the known plant Se metabolism and the sulfur (S) metabolism which it largely mirrors. We compile the current knowledge of plant selenometabolites, enzymes that handle this element and genes that affect Se uptake and tolerance. Large literature datasets are used to place Se in the overall elemental composition of land plants and to compare the transcriptome of Se-exposed Arabidopsis thaliana to the S deficiency response. Focus is placed on Se hyperaccumulator species, which can attain extremely high concentrations of Se in their tissues. We identify seven broad tolerance strategies to prevent Se toxicity, which itself has two faces: the oxidative stress of inorganic Se and the S-mimicking properties of organic Se compounds. This review, supplementary datasets and figures are intended as a comprehensive resource to guide plant Se research and help improve crop Se levels for a healthy future.