Zinc (Zn) is an important essential micronutrient for plants and humans; however, the exact transporter responsible for root zinc uptake from soil has not been identified. Here, we found that OsZIP9, a member of the ZRT–IRT-related protein, is involved in Zn uptake in rice (Oryza sativa) under Zn-limited conditions. OsZIP9 was mainly localized to the plasma membrane and showed transport activity for Zn in yeast (Saccharomyces cerevisiae). Expression pattern analysis showed that OsZIP9 was mainly expressed in the roots throughout all growth stages and its expression was upregulated by Zn-deficiency. Furthermore, OsZIP9 was expressed in the exodermis and endodermis of root mature regions. For plants grown in a hydroponic solution with low Zn concentration, knockout of OsZIP9 significantly reduced plant growth, which was accompanied by decreased Zn concentrations in both the root and shoot. However, plant growth and Zn accumulation did not differ between knockout lines and wild-type rice under Zn-sufficient conditions. When grown in soil, Zn concentrations in the shoots and grains of knockout lines were decreased to half of wild-type rice, whereas the concentrations of other mineral nutrients were not altered. A short-term kinetic experiment with stable isotope ⁶⁷Zn showed that ⁶⁷Zn uptake in knockout lines was much lower than that in wild-type rice. Combined, these results indicate that OsZIP9 localized at the root exodermis and endodermis functions as an influx transporter of Zn and contributes to Zn uptake under Zn-limited conditions in rice.

锌是植物和人类重要的必需微量营养素。但是，尚未确定负责从土壤中吸收根锌的确切转运蛋白。在这里，我们发现OsZIP9是ZRT–IRT相关蛋白的成员，在限制锌的条件下参与水稻（Oryza sativa）的锌吸收。OsZIP9主要位于质膜上，并显示了酵母（Saccharomyces cerevisiae）中锌的转运活性。表达模式分析表明，OsZIP9主要在所有生长期的根部表达，并且其缺锌表达上调。此外，OsZIP9在根成熟区域的真皮和真皮中表达。对于在低锌含量的水耕溶液中生长的植物，敲除OsZIP9会显着降低植物生长，同时在根部和枝条中均降低Zn浓度。然而，在锌充足的条件下，敲除品系和野生型水稻之间的植物生长和锌积累没有差异。当在土壤中生长时，基因敲除系的芽和籽粒中的锌浓度降低至野生型水稻的一半，而其他矿质养分的浓度保持不变。稳定同位素⁶⁷ Zn的短期动力学实验表明⁶⁷敲除品系中的锌吸收量远低于野生型水稻。结合起来，这些结果表明，位于水稻根外皮层和内胚层的OsZIP9充当了Zn的内向转运体，并有助于水稻在有限的Zn条件下对Zn的吸收。