School of Materials and Photon Science Institute, University of Manchester, Manchester, M13 9PL, UK.
Department of Plant Sciences, Rothamsted Research, Harpenden, AL5 2JQ, UK.
New Phytol. 2021 Aug;231(4):1644-1657. doi: 10.1111/nph.17440. Epub 2021 Jun 17.
Understanding the mechanisms of iron trafficking in plants is key to enhancing the nutritional quality of crops. Because it is difficult to image iron in transit, we currently have an incomplete picture of the route(s) of iron translocation in developing seeds and how the tissue-specific distribution is established. We have used a novel approach, combining iron-57 ( Fe) isotope labelling and nanoscale secondary ion mass spectrometry (NanoSIMS), to visualize iron translocation between tissues and within cells in immature wheat grain, Triticum aestivum. This enabled us to track the main route of iron transport from maternal tissues to the embryo through the different cell types. Further evidence for this route was provided by genetically diverting iron into storage vacuoles, with confirmation provided by histological staining and transmission electron microscopy energy dispersive X-ray spectroscopy (TEM-EDS). Almost all iron in both control and transgenic grains was found in intracellular bodies, indicating symplastic rather than apoplastic transport. Furthermore, a new type of iron body, highly enriched in Fe, was observed in aleurone cells and may represent iron being delivered to phytate globoids. Correlation of the Fe enrichment profiles obtained by NanoSIMS with tissue-specific gene expression provides an updated model of iron homeostasis in cereal grains with relevance for future biofortification strategies.
了解植物中铁的运输机制对于提高作物的营养价值至关重要。由于很难想象运输中的铁，我们目前对发育中的种子中铁的转运途径以及组织特异性分布是如何建立的，只有一个不完整的认识。我们采用了一种新方法，将铁-57（Fe）同位素标记与纳米二次离子质谱（NanoSIMS）相结合，在未成熟的小麦籽粒（Triticum aestivum）中可视化铁在组织间和细胞内的转运。这使我们能够追踪铁从母体组织向胚胎的主要运输途径，通过不同的细胞类型。通过将铁基因转入储存液泡来改变铁的运输途径，为这一途径提供了进一步的证据，组织学染色和透射电子显微镜能量色散 X 射线光谱（TEM-EDS）也证实了这一点。在对照和转基因谷物中，几乎所有的铁都存在于细胞内体中，这表明铁的运输是共质体运输，而不是质外体运输。此外，在糊粉层细胞中观察到一种富含 Fe 的新型铁体，可能代表铁被输送到植酸球。用 NanoSIMS 获得的 Fe 富集图谱与组织特异性基因表达的相关性，为谷物中铁稳态的更新模型提供了依据，这对未来的生物强化策略具有重要意义。
