As a significant component of monocot cell walls, (1,3;1,4)-β-glucan has conclusively been shown to be synthesized by the cellulose synthase-like F6 protein. In this study, we investigated the synthetic activity of other members of the barley (Hordeum vulgare) CslF gene family using heterologous expression. As expected, the majority of the genes encode proteins that are capable of synthesizing detectable levels of (1,3;1,4)-β-glucan. However, overexpression of HvCslF3 and HvCslF10 genes resulted in the synthesis of a novel linear glucoxylan that consists of (1,4)-β-linked glucose and xylose residues. To demonstrate that this product was not an aberration of the heterologous system, the characteristic (1,4)-β-linkage between glucose and xylose was confirmed to be present in wild type barley tissues known to contain HvCslF3 and HvCslF10 transcripts. This polysaccharide linkage has also been reported in species of Ulva, a marine green alga, and has significant implications for defining the specificity of the cell wall content of many crop species. This finding supports previous observations that members of a single CSL family may not possess the same carbohydrate synthetic activity, with the CSLF family now associated with the formation of not only (1,3)- and (1,4)-β-glucosidic linkages, but also (1,4)-β-glucosidic and (1,4)-β-xylosidic linkages.

中文翻译：

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纤维素合成酶样F基因家族的成员在陆地植物中合成了新型（1,4）-β-连接的木聚糖。

作为单子叶植物细胞壁的重要组成部分，已确定地显示（1,3; 1,4）-β-葡聚糖是由类似纤维素合酶的F6蛋白合成的。在这项研究中，我们使用异源表达调查了大麦（Hordeum vulgare）CslF基因家族其他成员的合成活性。如预期的那样，大多数基因编码能够合成可检测水平的（1,3; 1,4）-β-葡聚糖的蛋白质。但是，HvCslF3和HvCslF10的过表达基因导致合成了一种新的线性木聚糖，该木聚糖由（1,4）-β-连接的葡萄糖和木糖残基组成。为了证明该产物不是异源系统的畸变，已证实葡萄糖和木糖之间的特征性（1,4）-β-连接存在于已知包含HvCslF3和HvCslF10转录本的野生型大麦组织中。也已在Ulva物种中报道了这种多糖连接，一种海洋绿藻，对定义许多农作物物种的细胞壁含量的特异性具有重要意义。这一发现支持了先前的观察，即单个CSL家族的成员可能不具有相同的碳水化合物合成活性，而CSLF家族现在不仅与（1,3）-和（1,4）-β-糖苷键的形成有关。 ，但（1,4）-β-糖苷键和（1,4）-β-木糖苷键也是如此。