Selenium Differentially Regulates Flavonoid Accumulation and Antioxidant Capacities in Sprouts of Twenty Diverse Mungbean(Vigna radiata(L.)Wilczek)Genotypes

Seed germination with selenium(Se)is promising for producing Se-biofortified foods.Mungbean(Vigna radiata(L.)Wilczek)sprout is freshly eaten as a salad dressed with sauce,making it superior for Se biofortification.Since the Se safety range for the human body is extremely narrow,it is imperative to evaluate the genotypic responses of mungbean sprouts to Se.This study evaluated the Se enrichment capacity and interaction withflavonoids and antioxidant systems in sprouts of 20 mungbean germplasms.Selenium treatment was done by immersing mung-bean seeds in 20μM sodium selenite solution for 8 h.Afterward,the biomass,Se amounts,flavonoid(particularly vitexin and isovitexin)contents,antioxidant capacity,and key biosynthetic gene expressions were measured.Sprout Se content was 2.0-7.0μg g^(-1) DW among the 20 mungbean germplasms.Selenium treatment differentially affected the biomass,totalflavonoid,vitexin,isovitexin,antioxidant enzyme activities,and antioxidant capacities of the mungbean germplasms.Eight germplasms showed increased biomass(p<0.05),the highest increasing by 127%,but 13 did not phenotypically respond to Se treatment.Seven and six germplasms showed varied levels of vitexin and isovitexin increment after Se treatment,the highest measuring 2.67-and 2.87-folds for vitexin and isovitexin,respectively.Two mungbeanflavonoid biosynthesis genes,chalcone synthase(VrCHS)and chalcone isomerase(VrCHI)were significantly up-regulated in the germplasms with increased vitexin and isovitexin levels(p<0.05).Moreover,Se enrichment capacity was significantly correlated with the vitexin,isovitexin,and antiox-idant capacities.In conclusion,mungbean sprouts could be a useful Se-biofortified food,but the Se enrichment capacity and nutritional response must be determined for each germplasm before commercialization.

Selenium Regulates Antioxidant Capacities and Diterpenoid Biosynthesis in the Medicinal Plant Isodon rubescens

Dōng líng căo,the dried aboveground parts of Isodon rubescens(Hemls.)Hara.,is commonly consumed as a med-icinal decoction or tea beverage.Natural beverages can be an important source of human dietary selenium(Se).However,how I.rubescens plants respond to exogenous Se remains unknown.In this study,a pot cultivation experiment was employed to investigate the phenotypic and physiological responses of I.rubescens plants exposed to Se.Fifteen days after applying different concentrations of sodium selenate to the soil,the Se enrichment capa-city,growth indices,antioxidant capacities,and the content offlavonoids and diterpenoids were measured in the plants.Further,the oridonin content was quantified using the high-performance liquid chromatography method,and the expression levels of key diterpenoid synthesis genes were analyzed by quantitative real-time PCR(qRT-PCR).I.rubescens plants efficiently accumulated Se,with the Se content increasing proportionally to the applied dose,reaching levels of nearly 200 mg·kg^(-1) dry leaves as Se concentration increased.None of the three Se treat-ments significantly altered the phenotypic indices,except a longer root length occurred in the 3μM·kg^(-1) Se group.Among three Se doses,6μM·kg^(-1) Se gave the highest accumulation offlavonoids,diterpenoids,and oridonin,with the increase of 2.0-,1.8-,and 1.9-fold in aboveground parts,respectively.Selenium application boosted the activities of antioxidant enzymes and antioxidant capacities according to 2,2-Diphenyl-1-picrylhydrazyl(DPPH),ferric reducing/antioxidant power,and tea brewing color experiments.Four key synthase genes were upregulated significantly by 6μM·kg^(-1) Se treatment,notably 1-deoxy-D-xylulose 5-phosphate reductoisomerase(IrDXR),with a 5-fold increase,and kaurene synthase-like 4(IrKSL4),with a 6-fold increase.Thus,Se application in I.rubescens cultivation may be a potential biofortification method to supplement Se while increasingflavonoid and diterpenoid contents.