Variação genotípica no acúmulo e expressão de genes relacionados à assimilação de selênio em cultivares de trigo

Abstract

Selenium (Se) is considered essential for plants and animals because is glutathione peroxidase’s component and others selenoproteins. In plants, this element is not considered essential, but low doses can promote benefic effects. In this sense, it was realized two studies with different wheat genetic materials. In the first, the aim was to evaluate the effect of selenate to the biofortification, nutrition with macro and micronutrients and the expression of some genes involved in Se uptake and assimilation. In the second study, the aim was to advance the knowledge of Se biofortification by influence of selenate and selenite, in addition to evaluate how the Se application influences the nutrition with sulfur (S) in wheat plants. The experiments were conducted in pots with nutrient solution. The plants were arranged in a completely randomized design. The first study was installed in a factorial design 12 x 2, with twelve genotypes of wheat and presence (13 µmol L-1) or absence of selenium in the solution, with three replicates. In the second study, were realized three experiments: “seedling” – factorial design 7 x 2 x 4 with additional, seven cultivars, two sources of Se (selenate and selenite) and four doses of Se (0, 1, 5 and 10 M) with additional of 20 M of selenate, with four replicates; “seed production” – factorial design 3 x 2, three cultivars and presence (5 M of selenate) or absence, with four replicates and the experiment about absorption kinects of S. In the first study, the production and growth of genotypes were not affected by Se application. The Se concentration and content in the grains showed difference to the genetic materials evaluated. Eight genotypes in the shoot and five in the grains increased S concentration with selenate application. The genes expression doesn’t permit identify a standard of behavior of genotypes evaluated. In the second study, the different Se concentrations and forms promoted divergent effects for the plant growth and mineral concentrations in the shoots and roots for wheat plants. Both selenite and selenite increased the dry matter production of roots and shoots by low dosage (5 M). The increasing concentrations of selenate supply to 10 M not only continuously increased Se content, but also raised S level in shoots. The stimulation of S content by selenate in wheat shoots appeared to be due to a combination of a selenate-promoted expression of SULTR1;1 and SULTR1;3 with enhanced capacity of uptake, a reduced expression of SULTR4;1 to limit efflux of sulfate from the vacuoles, and a reduced expression of APS1 and APR2 to decrease S assimilation.