Several plant species, such as
Brassicaceae plants have the ability to effectively accumulate selenium (Se) in salubrious chemical forms. Here we investigated the beneficial effects of selenium as a micronutrient in broccoli sprout with a particular focus on its defense system against oxidative stress. We first generated a Se-enriched type of broccoli sprout by cultivating the plant in seleniferous medium. The Se-enriched plants showed a tendency to growth stimulation and significantly accumulated selenite, selenocysteine,
Se-methylselenocysteine, andγ-glutamyl
Se-methylselenocysteine, which were not detected in the plants grown without Se. Se-enriched plants also contained larger amounts of glutathione compared with Se-untreated plants, but otherwise the two types of plants appear to be comparable with respect to antioxidative potential under normal growth conditions. By contrast, Se-enriched plants developed a clearer predominance over Se-untreated ones in the tolerance to oxidative stress when exposed to paraquat such that generation of malondialdehyde and superoxide radical, a molecular readout of oxidative damage, was attenuated and conversely dehydroascobate reductase and glutathione reductase were upregulated along with increase in glutathione content. In addition, production of
Se-methylselenocysteine and γ-glutamyl
Se-methylselenocysteine were found to be promoted in response to the paraquat treatment. Our present results indicate that a Se-dependent antioxidation network including glutathione and antioxidative enzymes drives the protective mechanism counteracting oxidative stress in broccoli sprout, in which the two seleno-amino acid derivatives may act as newly identified participants.
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