This Spanish study measured iron, zinc, manganese and copper separately in the embryo and endosperm of wild-type rice and six transgenic lines engineered to change nicotianamine and 2’-deoxymugineic acid levels. In wild-type seeds, the embryo held 102 µg/g zinc against 21 µg/g in the endosperm. Some transgenic lines raised endosperm zinc up to 2.5-fold.
Key numbers
- Wild-type zinc: 102 ± 2 µg/g in the embryo and 21 ± 1 µg/g in the endosperm (dry weight, Figure 3; Results, p. 8).
- Endosperm zinc rose 2.5-fold (N1), 1.8-fold (N2) and 2.5-fold (ND1) over wild type; embryo zinc fell by 40% in ND2 (Results, p. 8).
- The authors note that milling and polishing remove the metal-rich bran and embryo, leaving the endosperm (Introduction, p. 2).
Methods (brief)
Embryos and endosperms were dissected and analyzed by ICP-MS, and elemental distribution was imaged by laser ablation ICP-MS. Nicotianamine and 2’-deoxymugineic acid were quantified by chromatography and mass spectrometry.
Evidence fitness
The paper supports the point that the edible endosperm of polished rice carries much less zinc than the embryo and that genetic changes can raise endosperm zinc. The plants are experimental transgenic lines and wild-type controls, not market rice.
Limitations
Plant growing conditions and sample numbers per line are described in the methods but values are reported mainly in figures. Transgenic lines are not commercial varieties.
Related evidence
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