Mechanisms of selenium hyperaccumulation in plants: A survey of molecular, biochemical and ecological cues

• Published in: Biochimica et biophysica acta. General subjects Vol. 1862; no. 11; pp. 2343 - 2353
• Main Authors: Lima, Leonardo Warzea, Pilon-Smits, Elizabeth A.H., Schiavon, Michela
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.11.2018
• Subjects: animal nutrition; antioxidant activity; antioxidants; biotic stress; crops; Defense; ethylene; Evolution; gene expression regulation; genes; herbivores; humans; Hyperaccumulation; hyperaccumulators; jasmonic acid; metabolism; pathogens; Plants; salicylic acid; selenates; Selenium; stress tolerance; sulfates; Sulfur; surveys; toxicity; transporters; Hyperaccumulation; Evolution; Selenium; Plants; Sulfur; Defense
• ISSN: 0304-4165; 1872-8006; 1872-8006
• DOI: 10.1016/j.bbagen.2018.03.028

Selenium (Se) is a micronutrient required for many life forms, but toxic at higher concentration. Plants do not have a Se requirement, but can benefit from Se via enhanced antioxidant activity. Some plant species can accumulate Se to concentrations above 0.1% of dry weight and seem to possess mechanisms that distinguish Se from its analog sulfur (S). Research on these so-called Se hyperaccumulators aims to identify key genes for this remarkable trait and to understand ecological implications. This review gives a broad overview of the current knowledge about Se uptake and metabolism in plants, with a special emphasis on hypothesized mechanisms of Se hyperaccumulation. The role of Se in plant defense responses and the associated ecological implications are discussed. Hyperaccumulators have enhanced expression of S transport and assimilation genes, and may possess transporters with higher specificity for selenate over sulfate. Genes involved in antioxidant reactions and biotic stress resistance are also upregulated. Key regulators in these processes appear to be the growth regulators jasmonic acid, salicylic acid and ethylene. Hyperaccumulation may have evolved owing to associated ecological benefits, particularly protection against pathogens and herbivores, and as a form of elemental allelopathy. Understanding plant Se uptake and metabolism in hyperaccumulators has broad relevance for the environment, agriculture and human and animal nutrition and may help generate crops with selenate-specific uptake and high capacity to convert selenate to less toxic, anticarcinogenic, organic Se compounds. •Plants do not need Se, but Se-hyperaccumulators contain very high Se concentration.•Hyperaccumulators may have mechanisms that distinguish Se from its analog sulfur.•Hyperaccumulators have steady high expression of defense and sulfur-regulated genes.•Se hyperaccumulation evolved in some species in association to ecological benefits.•Unravelling Se hyperaccumulation mechanisms may improve Se phytotechnologies.