RESUMEN
The production of natural selenium (Se)-rich food by using a high-Se crop cultivar is beneficial to human health and environmental safety; however, the underlying mechanism of different Se-accumulation ability between high- and low-Se rice cultivars remains unclear. A low-grain-Se cultivar and high-grain-Se cultivar of rice were used as test materials, and two levels of Se (0 and 0.5 mg kg-1) were arranged in a randomized design containing twelve replicates. The dynamic changes of shoot Se concentration and accumulation, xylem sap Se concentration, shoot and grain Se distribution, Se transporters genes (OsPT2, Sultr1;2, NRT1.1B) expression of the high- and low-Se rice cultivars were determined. The shoot Se concentration and accumulation of the high-Se rice showed a greater degree of reduction than those of the low-Se rice during grain filling stage, indicating that leaves of high-Se rice served as a Se source and supplied more Se for the growth centre grain. The expression levels of OsPT2, NRT1.1B and Sultr1;2 in the high-Se rice cultivar were significantly higher than those in the low-Se rice cultivar, which indicated that the high-Se rice cultivar possessed better transport carriers. The distribution of Se in grain of the high-Se rice cultivar was more uniform, whereas the low-Se cultivar tended to accumulate Se in embryo end. The stronger reutilization of Se from shoots to grains promoted by increased transporters genes expression and optimized grain storage space may explain how the high-Se rice cultivar is able to accumulate more Se in grain.