The application of iron oxide nanoparticles (FeNPs) can alleviate cadmium (Cd) accumulation in rice. However, the effect of FeNPs on the interaction between Fe and Cd during uptake in rice roots remains poorly understood. Herein, Fe₂O₃ NPs were applied to rice in a hydroponic experiment under Cd stress. The application of FeNPs significantly decreased the Cd concentrations in roots and shoots and reduced the Fe concentration in shoots. Fe plaque formation was significantly enhanced either by FeNPs or Cd stress; however, the ratios of Cd_{Fe plaque}/Cd_{whole plant} and Cd_{Fe plaque}/Fe_{Fe plaque} indicated that the contribution of Fe plaque to alleviating Cd uptake was limited. Gene expression quantification suggested that the presence of FeNPs inhibited the uptake of Fe²⁺ and Cd²⁺ via OsNRAMP5, OsCd1, OsIRT1 and OsIRT2 transporters, but it facilitated the uptake of Fe(III) via the OsYSL15 transporter. TEM-EDS evidenced the accumulation of FeNP aggregates in both the symplast and apoplast of roots, particularly in the symplast, which strongly restricted the root-to-shoot translocation of Cd and Fe, resulting in the Fe accumulation in shoots being even lower than those without FeNPs. This study provides a comprehensive understanding of the regulation mechanisms of Fe and Cd uptake in rice roots by FeNPs from the perspectives of Fe plaque, gene expression, and NP accumulation. The finding that FeNP accumulation in rice roots restricted Fe translocation to the shoot suggested that further investigation needs to optimize the distribution of Fe to rice grains during FeNP application.

中文翻译：

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铁（III）氧化物纳米颗粒对水稻根部铁和镉吸收的调节：铁斑形成、基因表达和纳米颗粒积累的见解

氧化铁纳米颗粒（FeNPs）的应用可以减轻水稻中镉（Cd）的积累。然而，FeNPs 在水稻根系吸收过程中对 Fe 和 Cd 相互作用的影响仍然知之甚少。在此，Fe ₂ O ₃ NPs 在镉胁迫下的水培实验中被施用于水稻。FeNPs的施用显着降低了根和地上部的Cd浓度，降低了地上部的Fe浓度。FeNPs或Cd胁迫显着增强了Fe斑块的形成；而 Cd _{Fe 菌斑}/Cd_全株与 Cd _{Fe 菌斑}/Fe _{Fe 菌斑的比值}表明铁斑对减轻镉吸收的贡献是有限的。基因表达定量表明，FeNPs的存在抑制了通过OsNRAMP5、OsCd1、OsIRT1和OsIRT2转运蛋白对Fe ²⁺和Cd ²⁺ 的吸收，但促进了通过OsYSL15对Fe( III )的吸收。运输者。TEM-EDS表明FeNP聚集体在根的共质体和质外体中都有积累，特别是在共质体中，这强烈限制了Cd和Fe的根-茎易位，导致茎中Fe的积累甚至低于那些没有 FeNPs。本研究从Fe斑块、基因表达和NP积累的角度全面了解FeNPs对水稻根系吸收Fe和Cd的调控机制。水稻根系中 FeNP 积累限制了 Fe 向茎部转移的发现表明，需要进一步研究在 FeNP 施用过程中优化 Fe 在水稻籽粒中的分布。