Dynamic Changes in the Distribution of Minerals in Relation to Phytic Acid Accumulation during Rice Seed Development
Dynamic Changes in the Distribution of Minerals in Relation to Phytic Acid Accumulation during Rice Seed Development
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DOI：
10.1104/pp.112.206573
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发表时间：
2012-12-01
期刊：
影响因子：
7.4
通讯作者：
Yoshida, Kaoru T.
中科院分区：
文献类型：
--
作者：
Iwai, Toru;Takahashi, Michiko;Yoshida, Kaoru T.
植酸(六磷酸肌醇[InSP(6)])是种子中磷的储存化合物。由于植酸与金属阳离子结合很强，它还可以作为金属的储存化合物。为了了解与植酸贮藏相关的金属积累和定位的机制，我们应用基于同步加速器的X射线显微荧光成像分析方法，表征了一些矿质元素(磷、钙、钾、铁、锌和铜)在未成熟和成熟的水稻种子中的同时亚细胞分布。这种精细成像方法可以揭示这些元素是否共定位。测定了它们的积累规律以及种子发育过程中磷和InSP(6)含量的变化。在种子发育过程中，种子外部InSP(6)含量迅速增加，而种子外部和内部的磷酸盐含量均较低。磷、钙、钾和铁在糊粉层中含量最丰富，并在种子发育过程中共存。锌广泛分布于糊粉层至内胚乳。铜定位于糊粉层外，不与磷共定位。根据这些结果，我们认为，从源器官转运的磷立即转化为InSP(6)并在糊粉层细胞中积累，钙、钾和铁在糊粉层中以植酸盐(植酸盐)的形式积累，而锌与InSP(6)松散结合，不仅在植酸盐中积累，而且还以另一种储存形式积累。铜在胚乳中积累，并可能表现出植酸盐以外的储存形式。
Phytic acid (inositol hexakisphosphate [InsP(6)]) is the storage compound of phosphorus in seeds. As phytic acid binds strongly to metallic cations, it also acts as a storage compound of metals. To understand the mechanisms underlying metal accumulation and localization in relation to phytic acid storage, we applied synchrotron-based x-ray microfluorescence imaging analysis to characterize the simultaneous subcellular distribution of some mineral elements (phosphorus, calcium, potassium, iron, zinc, and copper) in immature and mature rice (Oryza sativa) seeds. This fine-imaging method can reveal whether these elements colocalize. We also determined their accumulation patterns and the changes in phosphate and InsP(6) contents during seed development. While the InsP(6) content in the outer parts of seeds rapidly increased during seed development, the phosphate contents of both the outer and inner parts of seeds remained low. Phosphorus, calcium, potassium, and iron were most abundant in the aleurone layer, and they colocalized throughout seed development. Zinc was broadly distributed from the aleurone layer to the inner endosperm. Copper localized outside the aleurone layer and did not colocalize with phosphorus. From these results, we suggest that phosphorus translocated from source organs was immediately converted to InsP(6) and accumulated in aleurone layer cells and that calcium, potassium, and iron accumulated as phytic acid salt (phytate) in the aleurone layer, whereas zinc bound loosely to InsP(6) and accumulated not only in phytate but also in another storage form. Copper accumulated in the endosperm and may exhibit a storage form other than phytate.