DataSheet_1_Structural Imaging of Native Cryo-Preserved Secondary Cell Walls Reveals the Presence of Macrofibrils and Their Formation Requires Normal Cellulose, Lignin and Xylan Biosynthesis.pdf

The woody secondary cell walls of plants are the largest repository of renewable carbon biopolymers on the planet. These walls are made principally from cellulose and hemicelluloses and are impregnated with lignin. Despite their importance as the main load bearing structure for plant growth, as well as their industrial importance as both a material and energy source, the precise arrangement of these constituents within the cell wall is not yet fully understood. We have adapted low temperature scanning electron microscopy (cryo-SEM) for imaging the nanoscale architecture of angiosperm and gymnosperm cell walls in their native hydrated state. Our work confirms that cell wall macrofibrils, cylindrical structures with a diameter exceeding 10 nm, are a common feature of the native hardwood and softwood samples. We have observed these same structures in Arabidopsis thaliana secondary cell walls, enabling macrofibrils to be compared between mutant lines that are perturbed in cellulose, hemicellulose, and lignin formation. Our analysis indicates that the macrofibrils in Arabidopsis cell walls are dependent upon the proper biosynthesis, or composed, of cellulose, xylan, and lignin. This study establishes that cryo-SEM is a useful additional approach for investigating the native nanoscale architecture and composition of hardwood and softwood secondary cell walls and demonstrates the applicability of Arabidopsis genetic resources to relate fibril structure with wall composition and biosynthesis.

植物木质次生细胞壁是地球上储量最大的可再生碳基生物聚合物储存库。这类细胞壁主要由纤维素与半纤维素构成，并浸渍有木质素。尽管其作为植物生长核心承重结构的生物学意义重大，同时作为工业原料与能源来源的产业价值显著，但目前学界尚未完全阐明细胞壁内各组分的确切排布方式。我们对低温扫描电子显微镜（cryo-SEM）进行适配改造，用于对处于天然水合状态的被子植物与裸子植物细胞壁的纳米级结构进行成像。本研究证实，细胞壁宏原纤维——直径超过10纳米的圆柱形结构——是天然硬木与软木样本的常见特征。我们在拟南芥（Arabidopsis thaliana）次生细胞壁中也观测到了同类结构，这使得我们能够对比分析纤维素、半纤维素及木质素合成通路受干扰的突变株系间的宏原纤维差异。分析结果表明，拟南芥细胞壁中的宏原纤维依赖于纤维素、木聚糖与木质素的正常生物合成，或由这些组分构成。本研究证实，低温扫描电子显微镜是研究硬木与软木次生细胞壁天然纳米级架构与组分构成的有效补充手段，并证明了拟南芥遗传资源可用于关联纤维结构与细胞壁组分及生物合成过程。