INRA UR1268 Biopolymers, Interactions Assemblies, F-44316 Nantes, France.
J Exp Bot. 2011 Jan;62(3):1001-15. doi: 10.1093/jxb/erq332. Epub 2010 Nov 9.
The wild grass Brachypodium distachyon has been proposed as an alternative model species for temperate cereals. The present paper reports on the characterization of B. distachyon grain, placing emphasis on endosperm cell walls. Brachypodium distachyon is notable for its high cell wall polysaccharide content that accounts for ∼52% (w/w) of the endosperm in comparison with 2-7% (w/w) in other cereals. Starch, the typical storage polysaccharide, is low [<10% (w/w)] in the endosperm where the main polysaccharide is (1-3) (1-4)-β-glucan [40% (w/w) of the endosperm], which in all likelihood plays a role as a storage compound. In addition to (1-3) (1-4)-β-glucan, endosperm cells contain cellulose and xylan in significant amounts. Interestingly, the ratio of ferulic acid to arabinoxylan is higher in B. distachyon grain than in other investigated cereals. Feruloylated arabinoxylan is mainly found in the middle lamella and cell junction zones of the storage endosperm, suggesting a potential role in cell-cell adhesion. The present results indicate that B. distachyon grains contain all the cell wall polysaccharides encountered in other cereal grains. Thus, due to its fully sequenced genome, its short life cycle, and the genetic tools available for mutagenesis/transformation, B. distachyon is a good model to investigate cell wall polysaccharide synthesis and function in cereal grains.
野生短柄草（Brachypodium distachyon）被提议作为温带谷类作物的替代模式物种。本文报告了短柄草籽粒的特性，重点介绍了胚乳细胞壁。短柄草的细胞壁多糖含量很高，占胚乳的约 52%（w/w），而其他谷类作物的细胞壁多糖含量为 2-7%（w/w）。淀粉是典型的贮藏多糖，在胚乳中含量较低（<10%（w/w）），主要的多糖是（1-3）（1-4）-β-葡聚糖[占胚乳的 40%（w/w）]，它很可能作为一种贮藏化合物发挥作用。除了（1-3）（1-4）-β-葡聚糖外，胚乳细胞还含有大量的纤维素和木聚糖。有趣的是，短柄草籽粒中的阿魏酸与阿拉伯木聚糖的比例高于其他研究的谷类作物。阿魏酰阿拉伯木聚糖主要存在于贮藏胚乳的中层和细胞连接区，表明其在细胞-细胞黏附中可能发挥作用。本研究结果表明，短柄草籽粒含有其他谷类籽粒中遇到的所有细胞壁多糖。因此，由于其全基因组测序、短的生命周期以及可用于诱变/转化的遗传工具，短柄草是研究谷物细胞壁多糖合成和功能的良好模型。
