Selenium Biofortification in Radish Enhances Nutritional Quality via Accumulation of Methyl-Selenocysteine and Promotion of Transcripts and Metabolites Related to Glucosinolates, Phenolics, and Amino Acids

Abstract

Two selenium (Se) fertilization methods were tested for their effects on levels of anticarcinogenic selenocompounds in radish (Raphanus sativus), as well as other nutraceuticals. First, radish was grown on soil and foliar selenate applied 7 days before harvest at 0, 5, 10, and 20 mg Se per plant. Selenium levels were up to 1200 mg Se/kg DW in leaves and 120 mg Se/kg DW in roots. The thiols cysteine and glutathione were present at 2–3-fold higher levels in roots of Se treated plants, and total glucosinolate levels were 35% higher, due to increases in glucoraphanin. The only seleno-aminoacid detected in Se treated plants was Se-methyl-SeCys (100 mg/kg FW in leaves, 33 mg/kg FW in roots). The levels of phenolic aminoacids increased with selenate treatment, as did root total nitrogen and protein content, while the level of several polyphenols decreased. Second, radish was grown in hydroponics and supplied with 0, 5, 10, 20, or 40 μM selenate for 1 week. Selenate treatment led to a 20–30% increase in biomass. Selenium concentration was 242 mg Se/kg DW in leaves and 85 mg Se/kg DW in roots. Cysteine levels decreased with Se in leaves but increased in roots; glutatione levels decreased in both. Total glucosinolate levels in leaves decreased with Se treatment due to repression of genes involved in glucosinolates metabolism. Se-methyl-SeCys concentration ranged from 7–15 mg/kg FW. Aminoacid concentration increased with Se treatment in leaves but decreased in roots. Roots of Se treated plants contained elevated transcript levels of sulfate transporters (Sultr) and ATP sulfurylase, a key enzyme of S/Se assimilation. No effects on polyphenols were observed. In conclusion, Se biofortification of radish roots may be achieved via foliar spray or hydroponic supply. One to ten radishes could fulfill the daily human requirement (70 μg) after a single foliar spray of 5 mg selenate per plant or 1 week of 5–10 μM selenate supply in hydroponics. The radishes metabolized selenate to the anticarcinogenic compound Se-methyl-selenocysteine. Selenate treatment enhanced levels of other nutraceuticals in radish roots, including glucoraphanin. Therefore, Se biofortification can produce plants with superior health benefits.

Lettuce Biofortification with Selenium in Chitosan-Polyacrylic Acid Complexes

“…As in the present work, in another study [19] with radish plants using foliar applications of up to 20 mg Se per plant, no differences were found compared to the control in phenolic compounds. In contrast, in an experiment under field conditions of Allium cepa L. Se applied 50 µg/mL −1 increased the content of total phenolic compounds compared to the control [26].…”

“…− per plant, the authors [19] reported a decrease in dry weight of leaves and roots by about 35% and 18% respectively. On the other hand, when cultivating the radish plants in a soilless culture, they did not find significant differences in the dry weight of the leaves.…”

Enhancement Of Glucosinolate and Isothiocyanate Profiles in Brassicaceae Crops: Addressing Challenges in Breeding for Cultivation, Storage, and Consumer-Related Traits

“…Research has been conducted to apply selenium to crops (such as broccoli) to enhance nutritional properties 129 . Studies have shown that excess selenium application can reduce GSL content by 90% 30 .…”

Selenium Uptake and Biotransformation and Effect of Selenium Exposure on the Essential and Trace Elements Status: Comparative Evaluation of Four Edible Plants

“…cicla). Selenium effects in these plants had previously been [21][22][23][24][25][26][27], except for chard. Raphanus sativus belongs to Brassicaceae -a family of plants cataloged as primary accumulators of selenium and capable of synthesizing low molecular mass methyl-seleno compounds; as for nutritional value, this plant presents relatively high content of glucosinolates, phenolic compounds, vitamins, phytochemicals with possible anticancer activity, anthocyanins and is a good source of elements such as, K , Ca and Mg [28,29].…”