Collaborative Research: Extensin modules comprising self-assembling amphiphiles create scaffolds that nucleate cell wall formation: elucidation of roles and rules

植物细胞壁是由纤维素、半纤维素和果胶等互穿碳水化合物聚合物以及伸展蛋白的少量组分组成的自组装超分子结构。壁的性质产生于正确的自组装，但很少有人知道这是如何发生的。已知模式植物拟南芥中20种不同的延伸蛋白中的一种（RSH）对于新植物壁的正确形成至关重要，并且该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，其他组件在此基础上组织自己。这里的核心问题是伸展蛋白如何形成支架？伸展蛋白是具有交替的亲水性和疏水性氨基酸基序的高度重复的糖肽，具有丰富的带正电荷的氨基酸赖氨酸和组氨酸。将使用合成基因来替代rsh突变体中的RSH来测试这些延伸蛋白组分的功能。除了这种遗传学研究，纯化的RSH类似物和含有它们的壁将进行表征，生物化学的壁肽的分离和表征，包括交联测定，和生物药理学的模拟自组装成像使用原子力显微镜。该项目还旨在通过延伸蛋白类似物序列识别植物和壁的差异。确定延伸蛋白在初生细胞壁中的分子相互作用，以及保守肽基序的确切作用，对于理解壁自组装，防御反应和植物形态建成具有重要意义。作为地球上最丰富的生物质，植物细胞壁对从住所到食物，纤维和燃料的自我维持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，以实现植物细胞壁的新的和改进的用途，尤其是生物燃料的生产。包括少数民族在内的初级研究人员将作为跨多个科学学科的团队的一部分工作，以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.