ABSTRACT
The element selenium (Se) is chemically similar to sulfur (S). For this reason plants and other organisms mistakenly take up and metabolize Se via S transporters and biochemical pathways. This can cause toxicity due to a combination of (1) oxidative stress caused directly by selenocompounds and (2) replacement of S by Se in proteins and other S compounds, which disrupts their function. On the other hand, Se is an essential trace element for many organisms, including mammals, many bacteria, and certain green algae (Stadtman 1990, 1996, Fu et al. 2002). For higher plants, Se has been reported to be a bene’cial nutrient, but it has not been shown to be essential (Cartes et al. 2005, Djanaguiraman et al. 2005, Hartikainen 2005, Lyons et al. 2009, Pilon-Smits et al. 2009). Organisms that require Se produce essential proteins that contain selenocysteine (SeCys) in their active site. To date, no selenoproteins have been con’rmed to exist in higher plants (Novoselov et al. 2002).
