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Description
Tef (Eragrostis tef) is the most important cereal crop in the Horn of Africa, especially in Ethiopia and Eritrea, where it has been a staple for over 6000 years. Tef is a nutrient-dense crop containing high levels of micro (Fe, Mn, Zn) and macro (Ca, Mg) nutrients. However, the spatial distribution of mineral nutrients in tef seeds has never been analyzed before. By using the synchrotron-XRF microscopy, we determined the mineral distribution in seeds of various tef genotypes. Our findings showed that micronutrients are predominantly localized in tef seed embryos while macronutrients (Ca, K) are localized in both the seed coat and embryo. We also identified homolog of the iron-regulated transporters1 in tef (EtIRT1) and nicotianamine synthase2 (EtNAS2) genes via transcriptome analysis. Heterologous expression of the EtIRT1 and EtNAS2 in transgenic Arabidopsis increased Fe accumulation in the biomass and seeds in plants expressing both EtIRT1 and EtNAS2, while in rice, EtIRT1 expression increased Fe accumulation in the biomass only. We observed increased accumulation of micronutrients in transgenic Arabidopsis expressing the tef gene. In Arabidopsis seeds, Fe is preferentially localized in the vascular tissues of the hypocotyl and the cotyledons while Mn and Zn are localized in the cotyledon, and Cu is more concentrated in the embryo. Whereas in rice seeds, Fe, Mn and Zn are preferentially localized in the embryo with no marked difference between the wildtype and EtIRT1 expressing lines. This study reports the spatial distribution of minerals nutrients in seeds of the orphan crop tef for the first time, offering valuable information for future biofortification strategies.