A systemic analysis of cell wall protein networks in the cell walls of green organisms

植物细胞壁提供了地球上最大的生物量，并已被用于人类消费。鉴于目前对可再生能源和碳氢化合物来源的需求，研究的重点是如何促进将这种生物质转化为生物燃料。这项研究的长期目标是加深我们对植物生长发育过程中细胞壁生理的了解，从而指导利用植物生物量生产力的努力。主要的植物细胞壁蛋白是富含羟脯氨酸的糖蛋白(HRGP)，它与动物胶原蛋白有许多共同的特征。分子遗传学研究表明，HRGP在植物细胞壁的组装和重塑过程中起着至关重要的作用；然而，由于它们被嵌入到植物细胞壁中的复杂多糖中，它们的单独作用在很大程度上还没有被探索。因此，我寻求一种替代系统来研究HRGP的功能。一个绿藻模型系统衣藻，提供了一个很好的机会来探索与植物细胞壁相关的HRGP的细节，因为它具有与植物HRGP同源的HRGP家族，其细胞壁主要由HRGP组成，但很少或没有多糖，这使得显微和生化技术可以分析HRGP的分子特征。为了实现这一目标，我将系统地研究绿藻和植物之间的HRGP家族，并揭示在绿色生物中发挥基础作用的常见HRGP。其次，我将建立衣藻细胞壁功能缺陷突变体库。它们的表型和编码产物将共同阐明绿色生物如何进化出一个控制HRGP生物合成和组装的系统，以建立动态但强大的细胞外大分子网络。

Plant cell walls provide the largest biomass on earth and have been utilized for human consumption. Given the current need for renewable energy and hydrocarbon sources, research has been focused on how to facilitate conversion of this biomass into biofuels. The long-term goal of this study is to deepen our knowledge of plant cell wall physiology during growth and development, thereby guiding efforts to harness plant biomass productivity.The major plant cell wall proteins are hydroxyproline-rich glycoproteins (HRGPs) that share many features with animal collagens. Molecular genetics studies indicate that HRGPs play essential roles during plant cell wall assembly and remodeling; however, their individual roles have been largely unexplored as they are embedded in complex polysaccharides in plant cell walls. Therefore, I sought an alternative system to study the HRGP functions. A green algal model system Chlamydomonas, offers a great opportunity to probe the details of HRGPs relevant to plant cell walls, since it possesses HRGP families homologous to the plant HRGPs, and its cell walls consist mostly of HRGPs but little or no polysaccharides, which allows microscopic and biochemical techniques to analyze molecular features of HRGPs.Main objective of my research program is to understand biological functions of HRGPs in constructing cell walls. To achieve the objective, I will systemically examine HRGP families between green algae and plants, and uncover common HRGPs that would play fundamental roles in green organisms. Secondly, I will build a comprehensive library of the mutants defective in cell wall functions of Chlamydomonas. Their phenotypes and encoded products will collectively elucidate how green organisms evolve a system that controls biosynthesis and assembly of HRGPs in order to build dynamic but strong extracellular macromolecular networks.