Xylan and cellulose are abundant polysaccharides in vascular plants and essential for secondary cell wall strength. Acetate or glucuronic acid decorations are exclusively found on even-numbered residues in most of the glucuronoxylan polymer. It has been proposed that this even-specific positioning of the decorations might permit docking of xylan onto the hydrophilic face of a cellulose microfibril ^1-3 . Consequently, xylan adopts a flattened ribbon-like twofold screw conformation when bound to cellulose in the cell wall ⁴ . Here we show that ESKIMO1/XOAT1/TBL29, a xylan-specific O-acetyltransferase, is necessary for generation of the even pattern of acetyl esters on xylan in Arabidopsis. The reduced acetylation in the esk1 mutant deregulates the position-specific activity of the xylan glucuronosyltransferase GUX1, and so the even pattern of glucuronic acid on the xylan is lost. Solid-state NMR of intact cell walls shows that, without the even-patterned xylan decorations, xylan does not interact normally with cellulose fibrils. We conclude that the even pattern of xylan substitutions seen across vascular plants enables the interaction of xylan with hydrophilic faces of cellulose fibrils, and is essential for development of normal plant secondary cell walls.

中文翻译：

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木聚糖置换的均匀模式对于与纤维素在植物细胞壁中的相互作用至关重要。

木聚糖和纤维素是维管束植物中丰富的多糖，对于次级细胞壁强度至关重要。乙酸或葡萄糖醛酸装饰物仅出现在大多数葡糖醛酸木聚糖聚合物中偶数编号的残基上。已经提出装饰物的这种均匀的定位可以允许木聚糖对接到纤维素微原纤维^1-3的亲水面上。因此，木聚糖在细胞壁^4上与纤维素结合时采用扁平的带状双重螺旋构象。。在这里，我们显示了木聚糖特异性的O-乙酰基转移酶ESKIMO1 / XOAT1 / TBL29，对于拟南芥中木聚糖上乙酰酯的偶数生成而言是必需的。esk1突变体中乙酰化程度的降低使木聚糖葡萄糖醛糖苷转移酶GUX1的位置特异性活性失调，因此木聚糖上的葡萄糖醛酸均匀模式消失了。完整细胞壁的固态NMR显示，如果没有均匀图案的木聚糖装饰物，木聚糖不会与纤维素原纤维正常相互作用。我们得出的结论是，在维管植物上看到的木聚糖置换均匀模式能够使木聚糖与纤维素原纤维的亲水面相互作用，并且对于正常植物次生细胞壁的发育至关重要。