提出问题：While the structure of XyG has been well studied, much remains to be learned about its biosynthesis.

主要研究：Here we employed reverse genetics to investigate the role of Arabidopsis cellulose synthase like-C (CSLC) proteins in XyG biosynthesis.

结果-单突：We found that single mutants containing a T-DNA in each of the five Arabidopsis CSLC genes had normal levels of XyG.

结果-多突：However, higher-order cslc mutants had significantly reduced XyG levels, and a mutant with disruptions in all five CSLC genes had no detectable XyG. The higher-order mutants grew with mild tissue-specific phenotypes. Despite the apparent lack of XyG, the cslc quintuple mutant did not display significant alteration of gene expression at the whole-genome level, excluding transcriptional compensation. The quintuple mutant could be complemented by each of the five CSLC genes, supporting the conclusion that each of them encodes a XyG glucan synthase.

结果-进化：Phylogenetic analyses indicated that the CSLC genes are widespread in the plant kingdom and evolved from an ancient family.

结论：These results establish the role of the CSLCgenes in XyG biosynthesis, and the mutants described here provide valuable tools with which to study both the molecular details of XyG biosynthesis and the role of XyG in plant cell wall structure and function.

 摘  要 

木葡聚糖在大多数的植物中均是初生细胞壁的富含成分。虽然XyG的结构已经研究得很深入了，但是其生物合成方面的研究尚有欠缺。本文中，作者通过反向遗传学的方法研究了拟南芥类纤维素合酶CSLC蛋白在XyG生物合成中的作用。作者发现T-DNA插入的所有CSLC基因单突植株均具有正常的XyG含量。然而，高阶cslc植株中XyG水平显著下降，并且cslc五突植株中已经检测不到XyG了。高阶突变体生长具有轻度的组织特异性表型。尽管cslc五突植株中明显缺失了XyG，但是除了转录补偿以外，并未在全基因组水平上表现出明显的基因表达变化。cslc五突植株的缺陷表型可以被任何一个CSLC基因互补，说明它们每一个都编码一个XyG葡聚糖合酶。系统发育树显示CSLC基因在植物界广泛分布，从一个古老的家族演化而来。本文的研究结果揭示了CSLC基因在XyG生物合成中的作用，并且本文中的突变体为未来XyG生物合成的分子机制研究以及XyG在植物细胞壁结构和功能中的作用提供了宝贵的工具。