Interaction of Plant Cell Surface Macromolecules and Controlof Cell Expansion

9507191朱这项研究的长期目标是确定植物细胞表面蛋白在细胞分化和植物形态发生中的功能，并研究这些功能的潜在分子和细胞生物学基础。质膜阿拉伯半乳糖蛋白(AGPs)是一个丰富的蛋白多糖家族，被认为既能与细胞骨架相互作用，又能与细胞壁相互作用。用β-D-葡萄糖基Yariv抗原(一种选择性结合AGPs的小配体)处理拟南芥植株，表现为突变体reb(根表皮膨大)，表现为根表皮细胞膨大，根生长减慢和根急剧弯曲。这一观察首次有力地表明了细胞表面AGPs在控制细胞扩张方向和根发育中的作用，并预测reb突变体在根中含有缺陷AGPs。为了验证这一假说，将进行进一步研究，以检验Yariv抗原处理对拟南芥根发育的影响。用交叉电泳法和免疫组织化学法对reb突变体的AGP进行分析。为了了解AGP功能的潜在机制，将使用几种新的方法来表征AGPs与其他细胞表面大分子之间的相互作用。此外，还将分离和鉴定对B-D-葡萄糖基Yariv抗原不敏感的拟南芥突变体。这些突变体将有助于识别控制AGPs与其细胞表面配体之间相互作用的基因座。这种综合的生化、分子和遗传学方法将使我们能够牢固地确立细胞表面AGP在控制细胞扩张和根发育中的作用，并使我们能够更好地理解这种功能的潜在分子和细胞生物学机制。

9507191 Zhu The long-term objectives of this research are to determine the functions of plant cell surface proteins in cell differentiation and plant morphogenesis, and to study the underlying molecular and cell biological basis of such functions. Plasma membrane arabinogalactan-proteins (AGPs) are a family of abundant proteoglycans that are thought to interact with both the cytoskeleton and cell wall. Arabidopsis plants treated with Beta-D-glucosyl Yariv antigen (a small ligand that selectively binds AGPs), phenocopy the reb (root epidermal bulger) mutants which display root epidermal cell bulging, reduced root growth and sharp root bending. This observation strongly suggests for the first time a role of cell surface AGPs in the control of direction of cell expansion and root development, and predicts that the reb mutants contain defective AGPs in the root. To test this hypothesis, studies will be carried out to further examine the effect of Yariv antigen treatment on Arabidopsis root development. AGPs in reb mutants will be analyzed using crossed electrophoresis and immuno- histochemistry. To understand the underlying mechanisms of AGP function, several novel approaches will be employed to characterize the interactions between AGPs and other cell surface macromolecules. Furthermore, Beta-D-glucosyl Yariv antigen-insensitive Arabidopsis mutants will be isolated and characterized. The mutants will be useful in identifying loci that control the interaction between AGPs and their cell surface ligands. This integrated biochemical, molecular, and genetic approach will enable us to firmly establish a role for cell surface AGPs in the control of cell expansion and root development, and allow a better understanding of the underlying molecular and cell biological mechanisms for such a function.