Collaborative Research: Extensin Modules Comprising Self-Assembling Amphiphiles Create Scaffolds that Nucleate Cell Wall Formation: Elucidation of Roles and Rules

植物细胞壁是一种自组装的超分子结构，由相互渗透的碳水化合物聚合物组成：纤维素、半纤维素和果胶，以及延伸蛋白的少量成分。壁的性质产生于正确的自组装，但人们对其如何发生知之甚少。众所周知，在模式植物拟南芥中，20种不同的延伸蛋白中有一种（RSH）对于新植物壁上的正确形成至关重要，并且这种延伸蛋白具有自组装形成支架的能力。有几条证据表明扩展提供了模板，其他组件可以在模板上组织自己。这里的核心问题是扩展蛋白是如何形成支架的？伸展蛋白是一种高度重复的糖肽，由亲水性和疏水性氨基酸基序交替组成，具有丰富的带正电的氨基酸赖氨酸和组氨酸。这些延伸蛋白成分的功能将使用合成基因来替代RSH突变体中的RSH进行测试。除了遗传学研究之外，纯化的RSH类似物和含有它们的壁将通过分离和表征壁肽（包括交联试验）进行生物化学表征，并通过原子力显微镜对类似物自组装进行生物物理成像。该项目还旨在通过扩展模拟序列识别植物和墙壁的差异。确定原代细胞壁中延伸蛋白的分子相互作用，以及保守肽基序的精确作用，对理解细胞壁自组装、防御反应和植物形态发生具有重要意义。作为地球上最丰富的生物质，植物细胞壁从住所到食物、纤维和燃料，对自我维持的文明做出了至关重要的贡献。这项工作的一个潜在影响是细胞壁重塑，使植物细胞壁的新的和改进的用途，尤其是生物燃料的生产。包括少数族裔在内的初级研究人员将作为跨越多个科学学科的团队的一部分来解决这一重大的生物学问题。

The plant cell wall is a self-assembling supramolecular structure of interpenetrating carbohydrate polymers: cellulose, hemicellulose and pectin, and a minor component of extensin proteins. Wall properties arise from correct self-assembly, but very little is known about how this occurs. It is known that one (RSH) of the 20 different extensins in the model plant, Arabidopsis, is critical for correct formation on new plant walls and that this extensin has the capacity to self-assemble to form a scaffold. Several lines of evidence suggest that extensins provide templates on which other components organize themselves. The central question here is how do extensins form scaffolds? Extensins are highly repetitive glycopeptides of alternating hydrophilic and hydrophobic amino acid motifs, with an abundance of the positively charged amino acids lysine and histidine. Functionality of these extensin components will be tested using synthetic genes to replace RSH in the rsh mutant. In addition to this genetic study, purified RSH analogs and walls containing them will be characterized, biochemically, by isolation and characterization of wall peptides, including cross-linking assays, and biophysically by imaging of analog self-assembly using atomic force microscopy. The project also aims to identify plant and wall differences with extensin analog sequences. Defining the molecular interactions of extensins in the primary cell wall, and the precise roles of the conserved peptide motifs, are highly relevant to understanding wall self-assembly, defense responses and plant morphogenesis. As the most abundant biomass on earth, plant cell walls contribute crucially to self-sustaining civilizations from shelter, to food, fiber and fuel. A potential impact of this work is wall remodeling to enable new and improved uses of plant cell wall, not least the production of biofuels. Junior researchers including those with minority status will work as part of a team crossing several scientific disciplines to solve this significant biological problem.