Abstract
Rice is a staple food for over half of the world’s population, but it contains only low amounts of bioavailable micronutrients for human nutrition. Consequently, micronutrient deficiency is a widespread health problem among people who depend primarily on rice as their staple food. Iron deficiency anemia is one of the most serious forms of malnutrition. Biofortification of rice grains for increased iron content is an effective strategy to reduce iron deficiency. Unlike other grass species, rice takes up iron as Fe(II) via the IRON REGULATED TRANSPORTER (IRT) in addition to Fe(III)-phytosiderophore chelates. We expressed Arabidopsis IRT1 (AtIRT1) under control of the Medicago sativaEARLY NODULIN 12B promoter in our previously developed high-iron NFP rice lines expressing NICOTIANAMINE SYNTHASE (AtNAS1) and FERRITIN. Transgenic rice lines expressing AtIRT1 alone had significant increases in iron and combined with NAS and FERRITIN increased iron to 9.6 µg/g DW in the polished grains that is 2.2-fold higher as compared to NFP lines. The grains of AtIRT1 lines also accumulated more copper and zinc but not manganese. Our results demonstrate that the concerted expression of AtIRT1, AtNAS1 and PvFERRITIN synergistically increases iron in both polished and unpolished rice grains. AtIRT1 is therefore a valuable transporter for iron biofortification programs when used in combination with other genes encoding iron transporters and/or storage proteins.Electronic supplementary materialThe online version of this article (doi:10.1007/s11103-015-0404-0) contains supplementary material, which is available to authorized users.
Highlights
Iron deficiency is the most common and widespread nutrient deficiency, among children as well as women of childbearing age
These increase in iron content demonstrate the utility of the pMsENOD12B::AtIRT1 construct for iron biofortification in rice
Iron biofortification of rice endosperm to dietary sufficient RDA levels has proven much more challenging compared to previously successful β-carotene biofortification of rice (Paine et al 2005)
Summary
Iron deficiency is the most common and widespread nutrient deficiency, among children as well as women of childbearing age. Considering anemia as an indicator, 43 % of children, 38 % of pregnant woman and 29 % of non-pregnant women worldwide are estimated to be iron deficient (Steven et al 2013). The main causes of iron deficiency include low bioavailable iron in the diet, increased requirements in pregnancy, or excessive blood loss caused by injuries, intestinal parasitic infection or menstruation. Iron supplementation or food fortification are recommended interventions to overcome iron deficiency. Food fortification is considered the most effective and safest intervention in malaria-affected regions where iron supplementation leads to increased severity of the infectious disease (Oppenheimer et al 1986; Sazawal et al 2006). Rice is the main staple food for more than half of the world’s population and an important target crop for biofortification. Rice is a poor source of dietary iron because the micronutrient-rich aleurone, bran and husk of the grain are removed during
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