Promising role of selenium in mitigating the negative effects of iron deficiency in soybean leaves

Abstract

Little is known about the role of selenium (Se) in modulating the nutritional status and the non-enzymatic and enzymatic antioxidant defense system in iron(Fe)-deficient soybean. Hence, this work aimed to evaluate the possible beneficial effect of Se applied in the nutrient solution on photosynthetic pigments, nutritional status, reactive oxygen species accumulation, ascorbate and glutathione metabolites, activity of enzymes involved in the synthesis pathway of these metabolites, and antioxidant defense enzymes, including expression of superoxide dismutase (SOD) isoforms, after exposure to absence, deficiency, and sufficiency of Fe in combination with absence and presence of Se. The experimental design was completely randomized with 5 replications, containing 4 plants per pot. In this work, through physiological, biochemical, and molecular analyses, we observed a beneficial effect of Se in soybean plants with Fe suppression, mainly in the absence of Fe. Thus, in the absence of Fe with Se, there was higher remobilization of Fe and maintenance of foliar N concentration, which resulted in mitigation of leaf chlorosis and decreased loss of photosynthetic pigments. Additionally, under this cultivation condition, the main positive effect of Se was shown to be associated with the modulation of the glutathione cycle, with increases in the reduced glutathione and total glutathione content, reduced glutathione/oxidized glutathione ratio, and in the activity of the γ-glutamylcysteine synthetase, glutathione peroxidase, and glutathione reductase enzymes. The Se supply also reduced the need to replace SOD-Fe with SOD-Cu due to the positive modulation in the crosstalk between Fe and Cu, as well as attenuated the nutritional imbalance of Zn and Mn, mainly in the absence of Fe. These adjustments prevented lipid peroxidation and showed the beneficial role of Se in Fe-depleted plants.