• Iron (Fe) from rice grains is an important source of dietary intake; however, the molecular mechanisms responsible for loading of Fe to the grains are poorly understood.
• We functionally characterized a vacuolar iron transporter gene, OsVIT2 in terms of expression pattern, cellular localization, and mutant phenotypes.
• OsVIT2 was expressed in the parenchyma cell bridges of nodes, in the mestome sheath of leaf sheath and aleurone of the caryopsis. Mutation of OsVIT2 resulted in decreased Fe distribution to the leaf sheath, nodes, and aleurone, but increased Fe to the leaf blade and grains. Furthermore, Fe was heavily deposited in the parenchyma cell bridges, mestome sheath and aleurone in the wild‐type rice, but this accumulation was decreased in the knockout lines. Conversely, heavier deposition of Fe was observed in the embryo and endosperm of the grains of knockout lines compared with the wild‐type rice, resulting in increased Fe accumulation in the polished rice without yield penalty.
• These results indicate that OsVIT2 is involved in the distribution of Fe to the grains through sequestering Fe into vacuoles in mestome sheath, nodes, and aleurone layer and that knockout of this gene provides a potential way for Fe biofortification without yield penalty.

中文翻译：

---

液泡铁转运蛋白OsVIT2在铁向水稻籽粒分配中的作用

• 稻谷中的铁是膳食摄入的重要来源。然而，人们对导致铁负载到晶粒上的分子机理了解甚少。
• 我们在功能上表征了液泡铁转运蛋白基因OsVIT2的表达模式，细胞定位和突变表型。
• OsVIT2在结节的实质细胞桥，叶鞘的间质鞘和颖果的糊粉中表达。OsVIT2的突变导致铁在叶鞘，节和糊粉中的分布减少，但铁在叶片和谷粒中的分布增加。此外，铁大量沉积在野生型水稻的薄壁细胞桥，间质鞘和糊粉中，但在敲除品系中这种积累减少了。相反，与野生型水稻相比，在敲除品系的胚芽和胚乳中观察到铁的沉积较重，从而导致精制水稻中铁的积累增加而没有产量损失。
• 这些结果表明，OsVIT2通过将Fe螯合到流变鞘，节和糊粉层的液泡中而参与了Fe在谷物中的分布，并且该基因的敲除为Fe的生物强化提供了一种潜在的途径，而不会降低产量。