Pollination in Lilium longiflorum and Arabidopsis thaliana: The Role of Adhesion Molecules in Pollen Tube Cell Movement in the Style

这项植物繁殖研究的目标是描述携带精子细胞的花粉管和花柱之间的相互作用，在胚珠中将精子释放到卵细胞之前，花柱必须被花粉管穿过。从百合花柱中鉴定出两种黏附分子，它们负责花粉管细胞的黏附和引导。这是第一批在植物中被描述的黏附分子。在百合中，传输道是一层分泌的表皮，排列在花柱管内，花柱管排入子房。花粉管在柱头顶端的分泌表皮上萌发，并进入跟踪表皮表面的花柱。这些分泌物可以从解剖的花柱中分离出来，并用来制作体外花柱基质，作为粘附性试验。当花粉管被添加到这个检测系统中时，它们相互粘连，并附着在人造花柱基质上。用这种方法从柱头/花柱传输道中分离出两个黏附所必需的组分：一个是富含半胱氨酸的小分子9kD蛋白，另一个是大的果胶多糖(糖)。这两个分子本身都不是粘附性的；两者的结合是诱导花粉管与其他花粉管和花柱基质粘连所必需的。假设粘附性分子既参与引导管细胞到达胚珠，也参与伴随这种指导的管细胞运动机制。一种结合发育、细胞和分子生物学工具的多方面方法正被用于：1)破译百合中9kD蛋白与果胶相互作用诱导花粉管与花柱基质粘连的机制。2)利用百合和拟南芥建立了9kD蛋白在黏附中的作用的体内测试。3)了解细胞骨架在管状细胞运动和黏附中的作用。4)研究了百合和拟南芥花粉管顶端的生长。百合和拟南芥授粉系统中黏附分子的研究解决了两个主要问题：1)花粉管细胞与花柱细胞外基质黏附的机制是什么？2)黏附与花柱细胞运动有何关系？顶端生长的作用是什么？除了我们描述的两种授粉分子外，黏附分子在植物中还没有被描述，尽管黏附对植物的发育至关重要。在植物中很少发生这样的情况

0077886LordThe goals of this study of plant reproduction are to describe the interaction between the pollen tube, which carries sperm cells, and the style, which must be traversed by the pollen tube before the sperm can be released in the ovule to the egg cell. Two adhesion molecules have been identified from the style in lily that are responsible for pollen tube cell adhesion and guidance. These are the first adhesion molecules to be described in plants. In lily, the transmitting tract is a secreting epidermis that lines the stylar canal which empties into the ovary. Pollen tubes germinate on the secretory epidermis of the top of this canal, the stigma, and enter the style tracking the epidermal surface. These secretions can be isolated from dissected styles and used to make an in vitro stylar matrix which serves as an adhesion assay. When pollen tubes are added to this assay system, they adhere to each other and to the artificial stylar matrix. This assay was used to isolate two fractions from the stigma/stylar transmitting tract that are necessary for adhesion; one is a small cysteine rich 9kD protein and the other a large pectic polysaccharide (sugar). Neither of these molecules alone is adhesive; the combination of the two is necessary to induce pollen tube adhesion to other pollen tubes and to the stylar matrix.The hypothesis is that the adhesive molecules are involved both in guiding the tube cell to the ovule and in the mechanism of tube cell movement that accompanies this guidance. A multifaceted approach incorporating the tools of developmental, cell and molecular biology is being used to: 1) decipher the mechanism by which the 9kD protein in lily acts with a pectin to induce adhesion of the pollen tube to the stylar matrix. 2) develop an in vivo test for the 9kD protein's role in adhesion using both lily and Arabidopsis. 3) understand the role of the cytoskeleton in tube cell movement and adhesion. 4) study tip growth in both lily and Arabidopsis pollen tubes. The proposed work on adhesion molecules in the lily and Arabidopsis pollination systems addresses two major questions: 1) What is the mechanism of adhesion of the pollen tube cell to the stylar extracellular matrix? 2) How is adhesion related to tube cell movement and what is the role of tip growth? Adhesion molecules, other than the two we have described for pollination, have yet to be described in plants though adhesion is critical for plant development. There are few cases in plants where