Iron and zinc complexation in wild-type and ferritin-expressing wheat grain: implications for mineral transport into developing grain
Iron and zinc complexation in wild-type and ferritin-expressing wheat grain: implications for mineral transport into developing grain
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DOI：
10.1007/s00775-013-1000-x
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发表时间：
2013-06-01
影响因子：
3
通讯作者：
Shewry, Peter R.
中科院分区：
文献类型：
--
作者：
Neal, Andrew L.;Geraki, Kalotina;Shewry, Peter R.
我们使用基于同步加速器的 X 射线荧光和吸收技术来确定成熟小麦籽粒中的金属分布和络合作用。在植物中，扩展 X 射线吸收精细结构 (EXAFS) 光谱揭示了糊粉细胞和谷物转移区域的修饰糊粉细胞中的植酸铁和植酸锌结构：铁由六个氧原子和少于两个磷原子以八面体配位。锌在不对称配位壳中由四个氧原子和大约 1.5 个磷原子以四面体配位。我们还提供了过表达小麦铁蛋白的转基因谷物中两种金属络合发生改变的证据。对于锌来说，络合磷原子的数量始终加倍。尽管有一些 EXAFS 证据表明表达铁蛋白的谷物中存在植酸铁，但也有证据表明其结构缺乏磷。这种变化可能导致谷物储存区域内磷过量，进而导致表达铁蛋白的谷物中磷与锌的关联增加。衍生的 X 射线吸收光谱还表明，表达铁蛋白的谷物的转移区域中的矿物质络合与野生型谷物中的矿物质络合有很大不同。这可以解释为什么运输到发育中的谷物的矿物质水平升高在转基因谷物的折痕区域内积累。
We have used synchrotron-based X-ray fluorescence and absorption techniques to establish both metal distribution and complexation in mature wheat grains. In planta, extended X-ray absorption fine structure (EXAFS) spectroscopy reveals iron phytate and zinc phytate structures in aleurone cells and in modified aleurone cells in the transfer region of the grain: iron is coordinated octahedrally by six oxygen atoms and fewer than two phosphorous atoms. Zinc is coordinated tetrahedrally by four oxygen atoms and approximately 1.5 phosphorus atoms in an asymmetric coordination shell. We also present evidence of modified complexation of both metals in transgenic grain overexpressing wheat ferritin. For zinc, there is a consistent doubling of the number of complexing phosphorus atoms. Although there is some EXAFS evidence for iron phytate in ferritin-expressing grain, there is also evidence of a structure lacking phosphorus. This change may lead to an excess of phosphorus within the storage regions of grain, and in turn to the demonstrated increased association of phosphorus with zinc in ferritin-expressing grains. Derivative X-ray absorption spectra also suggest that mineral complexation in the transfer region of ferritin-expressing grains is quite different from that in wild-type grain. This may explain why the raised levels of minerals transported to the developing grain accumulate within the crease region of the transgenic grain.