Resumen de Estudi d aliments funcionals bi-fortificats amb se: interaccions i mecanismes competitius entre diferents elements mitjançant tècniques analítiques de sincrotró
Selenium (Se) is one of the essential micronutrients needed for proper metabolic function of humans. The form of the Se species and their concentration have a key role in their bioavailability. Se is incorporated into the human body from food sources. There is a direct correlation between the Se-deficient regions and poor Se availability to the population, challenging the recommended intake (55-70 μg of Se/day for adults). Plants have the natural ability to transform inorganic Se species to more bioavailable organic Se forms which are better assimilated by humans. However, there are several important aspects like the total Se accumulated, tolerable limits for the plants and humans, the species of Se assimilated in the plants, Se metabolism in crops, competing mechanisms with other soil pollutants that are yet to be addressed in detail to better design the fortification practices.
This study focuses on the Se-biofortification of wheat and it has two main objectives. Firstly, to analyse the competing behaviour of Se with pollutants (Cd or Hg) in hydroponic culture and, secondly, to assess how different Se application methods (soil-SA or foliar-FA) affect the Se species produced by the plant in soil culture. Overall, we are aiming to understand the mechanisms affected and the possible interaction in the plants with respect to Se concentration and the chemical transformation of Se species.
In hydroponic culture with Cd we found that the biomass and grain yield were reduced by the Se biofortification process, as well as by the Cd. SeMet and SeCyst are the major Se species found in Se biofortified grains, approximately 73% and 37%, respectively. In the presence of Cd, SeMeCys is forming while the amount of SeMet species gets reduced. Additionally, molecular gene expression studies on short term wheat plants exposed to Cd in hydroponic culture were performed on specific genes related with the effects from Se and Cd applications. S transporter genes is more expressed especially in Se6+ treatment as they directly compete with sulphate for plant uptake and the genes indicating metabolism shows major differences in Se4+ treatments (also in Cd presence), as Se(IV) could be transformed to organic species. The stress response genes affected by Cd presence were majority seen in shoots. Mercury (Hg) speciation in Se biofortified wheat plants grown hydroponically under Hg pollutant showed that the 50/50 mixture of Se4+/Se6+ species in the treatment reduces the accumulation of methylmercury in grains, offering protection against Hg to a certain extent.
Se biofortification in soil pot-culture is influenced by the solubility and mobility of Se species according to the soil properties (pH, organic matter, clay content, type of soil). No major changes on the biomass of roots and leaves has been detected as a function of the different Se treatments applied or by the application method. SA group, grains contain only C–Se–C species while in the case of FA a minor fraction (around 10%) of C–Se–Se–C species is present. The C–Se–C species are more bioavailable for humans, and that Se biofortification via SA is efficient than in FA in terms of the produced health benefits.
The thesis reports valuable information for achieving the formation of the desired Se species in wheat grains and reducing the toxicity to the plants, to finally gain better health benefits for the population.
