Calcium, pH and the Cytoskeleton in Pollen Tube Growth

花粉管生长是开花植物将雄性配子输送到卵细胞进行受精的过程，这是产生种子的必要前提。由于其经济意义和与植物细胞生长和发育的基本方面的相关性，延伸过程具有快速速率和高度极性的特点，因此引起了人们的极大兴趣。本项目重点关注钙（Ca2+）、质子（H+）和肌动蛋白细胞骨架的作用，并建立在最近的花粉管生长速度振荡的基础上，并且在离子和细胞骨架活性中都存在潜在的振荡。利用百合和烟草的花粉管，在高时间分辨率下，尝试将细胞内Ca2+和H+的振荡与生长速率的振荡联系起来。此外，还将探索当细胞壁特性被各种介质（如Ca2+、H+、硼、果胶甲基酯酶或Yariv苯糖苷）修饰时，这些振荡是如何改变的。通过确定这些药物是否以及如何改变振荡行为，以及它与细胞内Ca2+和H+的梯度以及这些离子的细胞外通量的关系，似乎有可能为控制生长的因素的活性建立一个时间层次。这里涉及的技术包括细胞内Ca2+和H+的比例成像，以及离子选择振动探针分析，以确定细胞外通量的大小和方向。在细胞骨架的研究中，将关注F-actin在clear区的结构和动态分布，这些元素在clear区的快速周转和形成被认为是发生的。将这些周转过程与生长的振荡模式联系起来将是特别有趣的，再次确定哪些事件发生在快速增长阶段之前，哪些事件发生在快速增长阶段之后。在这些研究中，新开发的GFP-talin融合将用于荧光标记活花粉管中的f -肌动蛋白。将这些研究结合起来，预计将对控制花粉管生长发育的生理和分子因素提供深入的了解。从某种程度上说，其他尖端生长细胞，如根毛、真菌菌丝、蕨类植物和苔藓原丝，也使用类似的机制，花粉管的结果可能是相关的，并帮助我们对细胞生长的基本机制有一个大致的了解。

Pollen tube growth is the process by which flowering plants deliver the male gamete to the egg apparatus for fertilization, a necessary prerequisite to seed production. Characterized by rapid rates and a high degree of polarity, the elongation process is of great interest, both because of its economic implications and its relevance to fundamental aspects of plant cell growth and development. This project focuses on the role of calcium (Ca2+), protons (H+), and the actin cytoskeleton, and builds upon the recent demonstration that pollen tube growth rate oscillates, and that there are underlying oscillations in both ions and cytoskeletal activity. Using pollen tubes of both lily and tobacco, an attempt will be made to correlate at high temporal resolution the oscillations in intracellular Ca2+ and H+ with those in the growth rate. In addition, an exploration will be made on how these oscillations are changed when cell wall properties are modified by various agents, e.g., Ca2+, H+, boron, pectin methyl esterase, or Yariv phenyl glycoside. By determining if and how these agents modify the oscillatory behavior, and its relationship to both the intracellular gradients of Ca2+ and H+ as well as the extracellular fluxes of these ions, it seems possible that a temporal hierarchy can be developed for the activity of factors that control growth. Techniques involved here include ratiometric imaging for intracellular Ca2+ and H+, and ion selective vibration probe analysis to determine the magnitude and direction of extracellular fluxes. In studies on the cytoskeleton, attention will be given to the structure and dynamic distribution of F-actin in the clear zone, where rapid turnover and formation of these elements is presumed to occur. It will be particularly interesting to correlate these turnover processes with the oscillatory pattern of growth, again with the view of determining which events precede the rapid growth phases and which events follow. For these studies the newly developed GFP-talin fusion will be used to fluorescently label F-actin in living pollen tubes.When taken together it is anticipated that these studies will provide insight into the physiological and molecular factors that control growth and development of the pollen tube. To the extent that other tip growing cells, e.g., root hairs, fungal hyphae, fern and moss protonemata, use similar mechanisms, the results from pollen tubes could be pertinent, and help us gain a general understanding of basic mechanisms involved in cell growth.