Effect of the Inorganic and Organic Selenium Compounds on the Growth and Gene Expression of Arabidopsis thaliana

Abstract

We evaluated the effect of inorganic and organic selenium compounds on the growth and gene expression of Arabidopsis thaliana. After the cultivation of A. thaliana at 25°C for 28 days with 0, 1, and 5 ppm inorganic (selenate and selenite) or organic (selenomethionine (SeMet), selenocystine (SeCystine), and Se-methylselenocysteine (MeSeCys)) selenium compounds, we measured the growth parameters, selenium content, and mRNA expression levels of the genes encoding the proteins involved in sulfur amino acid metabolism in the plant. Fresh weight of the plant was approximately 60% lower following an exposure to 1.0 ppm of the various selenium compounds. The selenium content was higher in the roots when exposed to SeMet while that was higher in the leaves when exposed to selenite. Exposure to organic selenium compounds corresponded to a significant decrease in the root weight, compared to that obtained with an exposure to inorganic selenium compounds. MeSeCys, at a level of 5.0 ppm, showed a weaker inhibition of growth compared to that recorded with any other selenium compound at that level. The weights of roots and leaves decreased depending on the selenium exposure levels up to 5.0 ppm. The expression levels of homocysteine S-methyltransferase 3 were increased following an exposure to 1.0 ppm selenate, SeMet, and SeCystine each. These results suggest that inorganic and organic selenium compounds show different effects on the growth parameters of A. thaliana.