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

阿拉伯半乳聚糖蛋白（AGPs）是一类广泛存在于植物中的富含羟脯氨酸的糖蛋白。 AGPs存在于细胞间隙、细胞壁和质膜中，并在生长和发育中发挥重要作用。 本研究的重点是从番茄DNA克隆中推导出一个质膜AGP突变体LeAGP-1，该突变体具有发育和器官特异性调控功能。 该克隆预测了一个新的、模块化的AGP，它由N端的信号肽、中心的经典AGP结构域和C端的跨膜结构域组成。 我们的工作假设是，LeAGP-1代表质膜AGP，它的功能是建立连接和介导粘附到细胞壁，类似于动物细胞粘附分子。 PI将通过以下方式检验这些假设并阐述LeAGP-1的结构和功能：1）从番茄细胞培养物中分离LeAGP-1并对其进行生物化学表征，以提供结构信息和用于功能表征的材料，2）在培养的细胞、茎和花以及证实膜和壁之间的粘附区的质化细胞中免疫定位LeAGP-1，和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）上表征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).