Biofortification of field-grown cassava by engineering expression of an iron transporter and ferritin

Abstract

Less than 10% of the estimated average requirement (EAR) for iron and zinc is provided by consumption of storage roots of the staple crop cassava (Manihot esculenta Crantz) in West African human populations. We used genetic engineering to improve mineral micronutrient concentrations in cassava. Overexpression of the Arabidopsis thaliana vacuolar iron transporter VIT1 in cassava accumulated three- to seven-times-higher levels of iron in transgenic storage roots than nontransgenic controls in confined field trials in Puerto Rico. Plants engineered to coexpress a mutated A. thaliana iron transporter (IRT1) and A. thaliana ferritin (FER1) accumulated iron levels 7–18 times higher and zinc levels 3–10 times higher than those in nontransgenic controls in the field. Growth parameters and storage-root yields were unaffected by transgenic fortification in our field data. Measures of retention and bioaccessibility of iron and zinc in processed transgenic cassava indicated that IRT1 + FER1 plants could provide 40–50% of the EAR for iron and 60–70% of the EAR for zinc in 1- to 6-year-old children and nonlactating, nonpregnant West African women.

The dual benefit of a dominant mutation in Arabidopsis IRON DEFICIENCY TOLERANT1 for iron biofortification and heavy metal phytoremediation

“…The production of nutritious, sufficient and safe food is a key objective of sustainable agriculture to feed the undernourished among the world’s population and includes crops such as Golden rice (Tang et al , ) to prevent vitamin‐A deficiency and iron‐biofortification of beans, sweet potato, legumes and cassava to combat the hidden hunger in developing countries (Garg et al , ). A biofortification study on cassava engineered Fe transporter IRT1 and ferritin to co‐express to enhance Fe levels (Narayanan et al , ). Other studies have manipulated components of the Fe homeostasis response, such as bHLH‐ IVc ( bHLH104/115/ILR3 ) and the downstream bHLH‐ 1b ( bHLH38/39/100/101 ), where overexpression of bHLH104 was studied for Cd tolerance by expressing metal detoxification‐associated genes, while high expression of bHLH104 transgene enhanced sensitivity to Fe deficiency (Yao et al , ).…”

“…Biofortification of plants through genetic engineering to improve Fe concentration is a direct approach that can be used to alleviate Fe deficiency. Genetic engineering has been applied to modify Fe transporters to generate Fe‐enriched crops (Kumar et al , ; Masuda et al , ; Narayanan et al , ).…”

European landrace diversity for common bean biofortification: a genome-wide association study

“…Iron and zinc deficiencies are widely spread nutritional disorders, affecting billions of people worldwide. Thanks to many efforts of the international research community, iron and zinc biofortification has been already achieved for some crops where major genes involved in the translocation of these minerals have been identified [62][63][64] . Regarding the common bean, efforts are still needed to develop better iron and zinc biofortified varieties also characterised by high bioavailability of these minerals.…”

Excellence in Cassava Breeding: Perspectives for the Future

“…Plants engineered to co-express a mutated A. thaliana iron transporter (IRT1) and ferritin (FER1) accumulated iron levels 7-18 times higher and zinc levels 3-10 times higher than those in non-transgenic controls in the field. Growth parameters and storage-root yields were unaffected by transgenic fortification [55].…”