title: A tale of two toxicities: malformed selenoproteins and oxidative stress both contribute to selenium stress in plants.
abstract: BACKGROUND
  Despite selenium's toxicity in plants at higher levels, crops supply most of the essential dietary selenium in humans. In plants, inorganic selenium can be assimilated into selenocysteine, which can replace cysteine in proteins. Selenium toxicity in plants has been attributed to the formation of non-specific selenoproteins. However, this paradigm can be challenged now that there is increasingly abundant evidence suggesting that selenium-induced oxidative stress also contributes to toxicity in plants.
  
  
  METHODS
  This Botanical Briefing summarizes the evidence indicating that selenium toxicity in plants is attributable to both the accumulation of non-specific selenoproteins and selenium-induced oxidative stress. Evidence is also presented to substantiate the claim that inadvertent selenocysteine replacement probably impairs or misfolds proteins, which supports the malformed selenoprotein hypothesis. The possible physiological ramifications of selenoproteins and selenium-induced oxidative stress are discussed.
  
  
  CONCLUSIONS
  Malformed selenoproteins and oxidative stress are two distinct types of stress that drive selenium toxicity in plants and could impact cellular processes in plants that have yet to be thoroughly explored. Although challenging, deciphering whether the extent of selenium toxicity in plants is imparted by selenoproteins or oxidative stress could be helpful in the development of crops with fortified levels of selenium.
authors.affiliation: Coastal Carolina University, Biology Department, Conway, SC 29526, USA.
authors.forename: Doug
authors.initials: D
authors.lastname: Van Hoewyk
mesh_terms: D008954:Models, Biological; D018384:Oxidative Stress; D018521:Plant Physiological Phenomena; D010940:Plant Proteins / Q000378:metabolism / Q000502:physiology; D010944:Plants / Q000187:drug effects* / Q000378:metabolism; D012643:Selenium / Q000502:physiology / Q000633:toxicity*; D051140:Selenoproteins / Q000378:metabolism / Q000502:physiology*
chemical_list: D010940:Plant Proteins; D051140:Selenoproteins; D012643:Selenium
keywords: Selenium toxicity; diselenide bonds; electron transport; glutathione; iron–selenium cluster; misfolded proteins; oxidative stress; proteasome; selenoproteins
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