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、半纤维素和果胶等碳水化合物聚合物组成的自组装超分子结构，是伸展蛋白的次要成分。墙的特性产生于正确的自组装，但人们对它是如何发生的知之甚少。已知模式植物拟南芥中20种不同的延伸素中的一种(RSH)对于在新的植物壁上正确形成是至关重要的，并且这种延伸素具有自组装形成支架的能力。有几条证据表明，扩展蛋白提供了模板，其他组件在此基础上进行自我组织。这里的中心问题是扩展蛋白是如何形成支架的？Extensins是由亲水和疏水氨基酸基序交替组成的高度重复的糖肽，含有丰富的带正电荷的氨基酸赖氨酸和组氨酸。将使用合成基因来取代RSH突变体中的RSH，以测试这些延伸素成分的功能。除了这项遗传学研究，纯化的RSH类似物和含有它们的壁将进行表征，生化上是通过分离和鉴定壁肽，包括交联分析，以及生物物理上是利用原子力显微镜对类似物自组装进行成像。该项目还旨在通过延伸素类似序列来识别植物和墙体的差异。确定初生细胞壁中伸展蛋白的分子相互作用，以及保守的多肽基序的精确作用，对于理解细胞壁自组装、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，植物细胞壁对从住所到食物、纤维和燃料的自给自足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壁面重塑，以实现植物细胞壁的新用途和改进用途，尤其是生产生物燃料。初级研究人员，包括那些具有少数民族身份的人，将作为一个跨越几个科学学科的团队的一部分，来解决这个重大的生物学问题。

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.