INRAE, UR BIA, F-44316, Nantes, France.
INRAE, UR BIA, F-44316, Nantes, France.
Plant Sci. 2021 May;306:110845. doi: 10.1016/j.plantsci.2021.110845. Epub 2021 Feb 10.
Cereal grains provide a substantial part of the calories for humans and animals. The main quality determinants of grains are polysaccharides (mainly starch but also dietary fibers such as arabinoxylans, mixed-linkage glucans) and proteins synthesized and accumulated during grain development in a specialized storage tissue: the endosperm. In this study, the composition of a structure localized at the interface of the vascular tissues of the maternal plant and the seed endosperm was investigated. This structure is contained in the endosperm cavity where water and nutrients are transferred to support grain filling. While studying the wheat grain development, the cavity content was found to autofluoresce under UV light excitation. Combining multispectral analysis, Fourier-Transform infrared spectroscopy, immunolabeling and laser-dissection coupled with wet chemistry, we identified in the cavity arabinoxylans and hydroxycinnamic acids. The cavity content forms a "gel" in the developing grain, which persists in dry mature grain and during subsequent imbibition. Microscopic magnetic resonance imaging revealed that the gel is highly hydrated. Our results suggest that arabinoxylans are synthesized by the nucellar epidermis, released in the cavity where they form a highly hydrated gel which might contribute to regulate grain hydration.
谷物为人类和动物提供了大量的热量。谷物的主要质量决定因素是多糖（主要是淀粉，但也包括膳食纤维，如阿拉伯木聚糖、混合链葡聚糖）和蛋白质，这些物质是在谷物发育过程中由专门的储存组织——胚乳合成和积累的。在这项研究中，研究了一个位于母体植物血管组织和种子胚乳界面的结构的组成。这个结构包含在胚乳腔中，水分和养分在那里转移以支持籽粒灌浆。在研究小麦籽粒发育时，发现腔内容物在紫外光激发下自发荧光。通过结合多光谱分析、傅里叶变换红外光谱、免疫标记和激光切割与湿法化学，我们在腔中鉴定出阿拉伯木聚糖和羟基肉桂酸。腔内容物在发育中的谷物中形成“凝胶”，在干燥成熟的谷物中以及随后的吸胀过程中仍然存在。微观磁共振成像显示，该凝胶高度水合。我们的结果表明，阿拉伯木聚糖是由珠心层表皮合成的，在腔中释放出来，形成一种高度水合的凝胶，可能有助于调节谷物的水合作用。
