Beneficial Role of Selenium (Se) Biofortification in Developing Resilience Against Potentially Toxic Metal and Metalloid Stress in Crops: Recent Trends in Genetic Engineering and Omics Approaches

Selenium (Se) is found in plants both in inorganic and organic forms as selenoamino acids and methylated complexes. Se influences growth and physiological parameters, viz. root and shoot growth, starch accumulation, water status regulation, respiration, germination promotion, nitrogen assimilation and delaying senescence in plants. Se deficiency causes many human medical conditions, viz. cancer, liver disease, cardiovascular disease, thyroid disease, Keshan disease and central nervous system disorders. Plants need Se to alleviate abiotic stresses, viz. high/low temperatures, drought, salinity, light, UV-B radiation and toxic metals/metalloids. Ameliorative role of Se, applied in relatively low doses, against abiotic stresses was mediated via enzymatic and non-enzymatic antioxidation. Chemical form, application method, edaphic presence and bioavailability of Se and its interaction with other elements regulate Se biofortification and abiotic stress tolerance in food and medicinal crops. Popular scientific search engines, viz. PubMed, Pubget, ScienceDirect, Medline, Scopus, SpringerLink, Mendeley, EMBASE, Google Scholar and JSTOR were searched to retrieve published articles by using pre-determined search strings involving “selenium”, “plants”, “stress”, “metals”, “metalloids”, etc. The retrieved literature encompasses the role of Se biofortification in enhancing dietary Se in crops and its bioavailability. The review also presents recent trends in Se-mediated amelioration of toxic metal and metalloid stresses via maintaining cell membrane integrity, functioning of photosynthetic machinery, inhibition against uptake and translocation of toxic metals and metalloids, control over the uptake and distribution of mineral nutrition and conversion of toxic metals and metalloids to non-toxic Se-metal complexes. Furthermore, current research on the genetic engineering and omics studies on Se biofortification and Se-mediated abiotic stress tolerance are also discussed. The present review comprehensively elucidates the beneficial role Se biofortification in developing resilience in crops against toxic metals and metalloids.