National Agri-Food Biotechnology Institute, Department of Biotechnology, C-127, Industrial Area, Phase-8, Mohali 160071, India.
J Exp Bot. 2013 Aug;64(11):3249-60. doi: 10.1093/jxb/ert160.
Iron insufficiency is a worldwide problem in human diets. In cereals like wheat, the bran layer of the grains is an important source of iron. However, the dietary availability of iron in wheat flour is limited due to the loss of the iron-rich bran during milling and processing and the presence of anti-nutrients like phytic acid that keep iron strongly chelated in the grain. The present study investigated the localization of iron and phosphorus in grain tissues of wheat genotypes with contrasting grain iron content using synchrotron-based micro-X-ray fluorescence (micro-XRF) and micro-proton-induced X-ray emission (micro-PIXE). X-ray absorption near-edge spectroscopy (XANES) was employed to determine the proportion of divalent and trivalent forms of Fe in the grains. It revealed the abundance of oxygen, phosphorus, and sulphur in the local chemical environment of Fe in grains, as Fe-O-P-R and Fe-O-S-R coordination. Contrasting differences were noticed in tissue-specific relative localization of Fe, P, and S among the different genotypes, suggesting a possible effect of localization pattern on iron bioavailability. The current study reports the shift in iron distribution from maternal to filial tissues of grains during the evolution of wheat from its wild relatives to the present-day cultivated varieties, and thus suggests the value of detailed physical localization studies in varietal improvement programmes for food crops.
铁缺乏是人类饮食中的一个全球性问题。在小麦等谷物中，谷粒的麸皮层是铁的重要来源。然而，由于在碾磨和加工过程中损失了富含铁的麸皮，以及存在植酸等抗营养物质，使铁在谷物中强烈螯合，因此小麦粉中铁的膳食可利用性有限。本研究使用基于同步加速器的微 X 射线荧光（micro-XRF）和微质子诱导 X 射线发射（micro-PIXE）技术，研究了不同铁含量的小麦基因型的谷粒组织中铁和磷的定位。X 射线吸收近边光谱（XANES）用于确定谷物中二价和三价铁的比例。结果表明，Fe 在谷物中的局部化学环境中存在大量的氧、磷和硫，如 Fe-O-P-R 和 Fe-O-S-R 配位。不同基因型之间在组织特异性的铁、磷和硫的相对定位上存在明显差异，这表明定位模式可能对铁的生物利用度有影响。本研究报告了铁在小麦从野生亲缘种到现代栽培品种的进化过程中从母体组织向子代组织的分布转移，因此表明在粮食作物的品种改良计划中进行详细的物理定位研究具有价值。
