Over‐expression of OsIRT1 leads to increased iron and zinc accumulations in rice

Abstract

Uptake and translocation of micronutrients are essential for plant growth. These micronutrients are also important food components. We generated transgenic rice plants overexpressing OsIRT1 to evaluate its functional roles in metal homeostasis. Those plants showed enhanced tolerance to iron deficiency at the seedling stage. In paddy fields, this over-expression caused plant architecture to be altered. In addition, those plants were sensitive to excess Zn and Cd, indicating that OsIRT1 also transports those metals. As expected, iron and zinc contents were elevated in the shoots, roots and mature seeds of over-expressing plants. This demonstrates that OsIRT1 can be used for enhancing micronutrient levels in rice grains.

Activation of Rice nicotianamine synthase 2 (OsNAS2) Enhances Iron Availability for Biofortification

“…However, it is unlikely due to accumulation of other toxic metals since NA preferentially binds to a few metals listed above. This yield reduction seen in our OsNAS2-D1 crop was much less critical compared with plants that over-express Fe-transporter genes (Lee and An, 2009;Lee et al, 2009a). Thus, considering the increase in bioavailable Fe content in those seeds, this small number of negative effects is tolerable.…”

“…Manipulation of the transporters involved in absorption and translocation of metals has been suggested as another approach for enhancing mineral contents if the amount of the transporter is rate-limiting (Ramesh et al, 2004). Overexpression of rice Fe transporters OsIRT1 and OsYSL15 also has resulted in a slight rise in Fe concentration in seeds (Lee and An, 2009;Lee et al, 2009a). When OsYSL2 is highly expressed in phloem cells by the OsSUT1 promoter, the Fe concentration in polished rice is up to 4.4-fold higher compared with the wild type (Ishimaru et al, 2010).…”

Detection of Chromosomal Regions Affecting Iron Concentration in Rice Shoots Subjected to Excess Ferrous Iron Using Chromosomal Segment Substitution Lines betweenJaponicaandIndica

“…Both OsIRT1 and OsIRT2 were reported to express predominantly in roots (Ishimaru et al, 2006), and over-expression of OsIRT1 by the transgenic method led to an increased shoot iron concentration (Lee and An, 2009). However, whether the OsIRT genes are related to the increased shoot iron concentration under the excess ferrous iron conditions, and whether there are genotypic differences in the OsIRT genes with the cultivar remain unknown.…”

Iron Uptake and Loading into Rice Grains

“…Rice plants overexpressing OsIRT1 also showed enhanced tolerance to Fe deficiency in paddy fields. These plants accumulated higher levels of Fe and Zn in shoots, roots, and mature seeds, indicating that OsIRT1 can be used to enhance micronutrient levels in rice grains (Lee and An 2009). The efforts to increase tolerance to Fe deficiency in alkaline soils have been reviewed recently ).…”