MOLECULAR MECHANISM OF POLLEN TUBE ELONGATION

花粉管伸长的分子机制

• 批准号: 2192165
• 负责人: Alice Y. Cheung
• 金额: $ 31.52万
• 依托单位: YALE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-08-01 至 1999-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2192165
• 关键词: cell migration; genetically modified plants; glycosylation; plant physiology; plant proteins; pollen; protein structure function; tissue /cell culture; tobacco

The goal for the present proposal is to understand the molecular mechanism underlying pollen tube elongation. Pollen tube elongation is a process central to plant sexual reproduction. After pollen is deposited on the receptive stigmatic surface of the female reproductive organ pistil, the male gametes are transported by pollen tube elongation to the ovary to fertilize the egg cell. Pollen tube elongation is a directed outgrowth from the pollen grain on the stigmatic surface toward the ovary which is located at the basal end of the pistil, hundreds to thousand times the diameter of pollen grains away. Pollen tube elongation is often compared to axon outgrowth in animal systems since it is a directed cell movement based on a tip growth process in the extracellular matrix of pistillate tissues. Similar to understanding the mechanism underlying axon outgrowth, studies on pollen tube elongation face the same challenges of the difficulty to decipher among mechanisms that are based on specific chemotactic attractants, or to surface structure adhesion, or to a lack of deliberate attraction and pollen tubes follow a path of least resistance. We have isolated and characterized the first protein component (TTS protein) and its cDNAs from pistillate tissues of tobacco which can promote pollen tube elongation and display properties suggesting it may contribute to the overall pistil mechanism of guiding pollen tubes towards the ovary. TTS protein is an arabinogalactan protein specifically located in the intercellular matrix of the stylar transmitting tissue, a specialized medium through which pollen tubes elongate from the stigma to the ovary. Our results show that TTS protein attains its pollen tube growth promotion activity by adhering to the surface and to the growth tips of pollen tubes which uptake and hydrolyze the sugar residues on these proteins. TTS proteins also display a gradient of increasing glycosylation levels from the stigmatic to the ovarian end of the transmitting tissue, the same direction as pollen tube growth. The proposed research focuses specifically on elucidating the molecular mechanism underlying the interactions between TTS protein and pollen tubes, on determining the contribution of its pollen tube surface adhesion properties and the mobilization of its sugar components by pollen tubes to its activity in promoting pollen tube elongation, and on examining the functional significance of the gradient of glycosylation levels associated with this protein. A combination of molecular, cellular, biochemical and transgenic approaches will be used. The biochemical parameters involved in the interaction between TTS protein and pollen tubes will be determined. The structure-functional relationship of TTS protein will be examined by generating modified TTS proteins and determining how these changes affect their pollen tube growth promoting activity and their interactions with pollen tubes. The participation of TTS proteins in the direction of pollen tube elongation will also be examined in vivo and in vitro. The proposed experiments together should yield a clear understanding of how a major transmitting tissue protein mediates its functions and demonstrate whether a sugar_gradient associated with this protein is chemotactically significant in directional pollen tube elongation. Understanding pollen tube elongation should extend our knowledge on cell migration in general.

本提案的目标是了解分子机制 底层花粉管伸长。花粉管伸长是一个过程 植物有性生殖的中心。花粉沉积在花粉上后 雌性生殖器官雌蕊的接受柱头表面 雄配子通过花粉管的伸长运输到卵巢 使卵细胞受精。花粉管伸长是定向生长 从柱头表面的花粉粒到子房 位于雌蕊基端，是雌蕊的数百至数千倍 花粉粒的直径。花粉管伸长常被比较 动物系统中的轴突生长，因为它是定向细胞运动 基于雌性细胞外基质中的尖端生长过程 组织。类似于了解轴突生长的机制， 花粉管伸长研究面临着与花粉管伸长相同的挑战 难以破译基于特定机制的机制 趋化引诱剂，或表面结构粘附，或缺乏 刻意的吸引和花粉管遵循阻力最小的路径。 我们分离并表征了第一个蛋白质成分（TTS 蛋白质）及其来自烟草雌蕊组织的 cDNA，可 促进花粉管伸长并显示特性表明它可能 有助于引导花粉管朝向的整体雌蕊机制 卵巢。 TTS 蛋白是一种阿拉伯半乳聚糖蛋白，专门位于 在花柱传递组织的细胞间基质中， 花粉管从柱头延伸到的特殊介质 卵巢。我们的结果表明 TTS 蛋白到达花粉管 通过粘附表面和生长来促进生长的活性 花粉管的尖端吸收并水解花粉管上的糖残留物 这些蛋白质。 TTS 蛋白也显示出增加的梯度 从柱头到卵巢末端的糖基化水平 传播组织，与花粉管生长方向相同。这 拟议的研究特别侧重于阐明分子 TTS蛋白与花粉相互作用的机制 管，确定其花粉管表面粘附的贡献 特性及其糖成分通过花粉管的动员 其促进花粉管伸长的活性，以及​​检查 相关糖基化水平梯度的功能意义 与这种蛋白质。分子、细胞、生物化学和 将使用转基因方法。涉及的生化参数 TTS 蛋白和花粉管之间的相互作用将被确定。 TTS蛋白的结构-功能关系将通过以下方式检查 生成修饰的 TTS 蛋白并确定这些变化如何影响 它们的花粉管生长促进活性及其与 花粉管。 TTS 蛋白参与花粉的方向 还将在体内和体外检查管伸长率。拟议的 一起进行实验应该可以清楚地了解一个专业如何 传输组织蛋白介导其功能并证明是否 与该蛋白质相关的糖梯度是趋化性的 对花粉管定向伸长有显着影响。 了解花粉 管伸长应该扩展我们对细胞迁移的一般知识。