Selenium Metabolism in Plants: Molecular Approaches

Selenium (Se) is placed in Group VIA of the Periodic Table. Its chemistry is similar to sulfur (S). Practically all small organic selenium compounds are isologues of corresponding sulfur compounds. With a few exceptions, they are also isologues of sulfur amino acids or derivatives thereof. Selenium plays an indispensable role for humans, animals and microorganisms. It is beneficial for the metabolism at lower concentrations, whereas at higher concentrations it becomes toxic. In other words, the range between deficiency and toxicity is very narrow. Short-term consumption of high levels of Se by human and animals may cause nausea, vomiting, and diarrhea, whereas chronic consumption of high concentrations of Se compounds can result in a disease called selenosis (Goldhaber, 2003). Excess selenium in the environment can be the result of either natural geological processes or industrialization.