Structure and Function of a Novel, Modular Arabinogalactan-Protein from Tomato

9727757；PI-Showter Arabinogalactan-Proteins(AGPs)是一类广泛存在于植物体内的富含羟基脯氨酸的糖蛋白家族。AGP存在于细胞间隙、细胞壁和质膜中，与生长发育密切相关。本研究的重点是从番茄DNA克隆中获得的突变型质膜AGP，LeAGP-1，它具有发育和器官特异性调控功能。这些克隆预测了一种新型的模块化AGP，它由N端信号肽、夹有基本亚区的中心经典AGP结构域和C端假定的跨膜结构域组成。我们的工作假设是LeAGP-1代表质膜AGP，其功能类似于动物细胞黏附分子，在建立连接和介导与细胞壁的黏附方面发挥作用。PIS将通过以下方式验证这些假设和解决的结构和功能：1)从番茄细胞培养中分离LeAGP-1并进行生化鉴定，为功能鉴定提供结构信息和材料；2)在培养细胞、茎和花以及展示膜与壁之间粘附区的胞质细胞中免疫定位LeAGP-1；以及3)在分子水平(分子间交联测试)和整个植物水平(转基因植物中的LeAGP-1反义抑制/正义共抑制)鉴定LeAGP-1的功能。

9727757; PI -- Showalter Arabinogalactan-proteins (AGPs) are a family of hydroxyproline-richglycoproteins which are widely distributed in plants. AGPs are found inintercellular spaces, cell walls, and plasma membranes and implicated toplay important roles in growth and development. This proposal focuses on aputative plasma membrane AGP, LeAGP-1, deduced from tomato DNA clones whichdemonstrate developmental and organ-specific regulation. The clonespredict a novel, modular AGP comprised of an N-terminal signal peptide, acentral classical AGP domain sandwiching a basic subdomain, and C-terminalputative transmembrane domain. Our working hypotheses are that LeAGP-1represents a plasma membrane AGP and that it functions in establishingconnections and mediating adhesion to the cell wall, analogous to animalcell adhesion molecules. The PIs will test these hypotheses and addressstructure and function of LeAGP-1 by: 1) isolating and biochemicallycharacterizing LeAGP-1 from tomato cell cultures to provide structuralinformation and material for functional characterization, 2)immunolocalizing LeAGP-1 in cultured cells, stems, and flowers and inplasmolyzed cells demonstrating zones of adhesion between the membrane andwall, and 3) functionally characterizing LeAGP-1 at the molecular level(tests for intermolecular crosslinking) and whole plant level (LeAGP-1antisense suppression/sense cosuppression in transgenic plants).