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This comprehensive review examines biofortification strategies for enhancing crop tolerance to metals and metalloids while improving nutritional quality. Global agriculture faces concurrent challenges from soil contamination, climate change, and micronutrient malnutrition, affecting over 2 billion people worldwide. Biofortification presents a multifaceted approach that simultaneously addresses these issues by enhancing essential nutrient content in crops while potentially conferring cross-tolerance to toxic elements. We analyze the complex mechanisms governing metal/metalloid uptake, translocation, and detoxification in plants, including transporter systems (ZIP, YSL, COPT, BOR, SULTR), chelation processes involving phytochelatins and metallothioneins, and compartmentalization strategies mediated by transcription factors (WRKY, NAC, MYB, bZIP), and epigenetic modifications. The review evaluates seven key biofortification targets: zinc, iron, copper, selenium, boron, silicon, and controlled arsenic, highlighting their distinct physiological roles and stress tolerance mechanisms. Zinc biofortification demonstrates competitive inhibition against cadmium uptake through shared transporter pathways, while iron enhancement promotes arsenite exclusion through plaque formation on root surfaces. Silicon creates physical barriers against metal translocation through phytolith formation and cell wall deposition, while selenium activates antioxidant response element (ARE) pathways, thereby mitigating oxidative stress through enhanced glutathione peroxidase activity. Recent advances in genetic engineering, including CRISPR-Cas9-mediated transporter modification and synthetic biology approaches, have accelerated the development of metal-efficient crop varieties with improved nutritional profiles and stress resilience. Emerging technologies such as nanomaterial-based biofortification and rhizosphere microbiome engineering offer promising avenues for sustainable agricultural intensification. However, significant knowledge gaps remain regarding genotype-specific responses, precise molecular cross-talk between nutrient enrichment and toxic element exclusion, and the integration of omics technologies for predictive biofortification modeling. This review systematically identifies these research gaps and proposes integrated approaches that enhance both crop resilience and nutritional security amid increasing environmental challenges.
Garg et al. (Mon,) studied this question.