Subcellular dynamics studies of iron reveal how tissue‐specific distribution patterns are established in developing wheat grains

Sadia Sheraz, Yongfang Wan, Eudri Venter, Shailender K. Verma, Qing Xiong, Joshua Waites, James M. Connorton, Peter R. Shewry, Katie L. Moore, Janneke Balk

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Abstract

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 ( 57Fe) 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 57Fe, was observed in aleurone cells and may represent iron being delivered to phytate globoids. Correlation of the 57Fe 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.

Original languageEnglish
Pages (from-to)1644-1657
Number of pages14
JournalNew Phytologist
Volume231
Issue number4
Early online date29 Apr 2021
DOIs
Publication statusPublished - Aug 2021

Keywords

  • NanoSIMS
  • aleurone
  • iron
  • nicotianamine
  • pulse-chase
  • trafficking
  • wheat

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