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Actin cytoskeleton regulates pollen tube growth and tropism.

机译：肌动蛋白细胞骨架调节花粉管的生长和向性。

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摘要

Fertilization in plants depends on the delivery of the sperm cells in the pollen grain through the pollen tube to the ovule. The pollen tube is a highly anisotropic, fast growing cellular protuberance. Because the pollen tube is non autotrophic, it requires a steady supply of carbohydrates and minerals supplied by the pistil to sustain its growth. These elements serve for the synthesis of cell wall material, delivered to the site of cell wall assembly in secretory vesicles that are transported along the actin cytoskeleton and deposited at the growing apex of the tube. The tube has to resist external deformation forces in order to maintain its cylindrical shape and to respond to various directional signals in order to reach its target. My objectives were to identify the role of the cytoskeleton in the anisotropic growth of the pollen tube and to determine how the tube responds to directional cues. The cytoskeleton in the pollen tube consists of microfilaments and microtubules, both forming long filamentous elements. For in vitro growing pollen tubes, carbohydrates and growth minerals have to be added to the growth medium in specific amounts order to sustain pollen tube growth. I optimized the growth conditions of Arabidopsis thaliana and Camellia japonica pollen tubes which, in addition to pollen from Lilium longiflorum, were used as model species for my experiments. I developed a microwave based, fast and efficient fixation and labelling protocol for pollen tubes. I used pharmacological, mechanical, molecular and microscopical tools to study the role of the cytoskeleton in pollen tube growth and tropism. I found that the actin cytoskeleton, and more specifically the subapical actin fringe, plays an important role in the regulation of pollen tube growth and architecture through the controlled delivery of secretory vesicles to the growing apex. I constructed a galvanotropic chamber that can be mounted on an inverted microscope to induce controlled tropic triggers. I found that the actin cytoskeleton is also involved in the ability of the pollen tube to change its direction. This tropic behaviour was shown to be dependent on the concentration of calcium ions in the growth medium and calcium influx through calcium channels. The cytosolic calcium gradient in the pollen tube regulates the activity of various actin binding proteins that are responsible for remodelling the actin cytoskeleton. Among these proteins are two Arabidopsis gametophyte-specific actin depolymerizing factors (ADFs) that I tagged with two intrinsically fluorescent proteins. I found that ADF7 and ADF10 are differentially expressed during microsporogenesis and pollen tube germination and growth and that they likely divide important functions between them.;Keywords: Actin, actin depolymerizing factor, Arabidopsis thaliana, calcium, Camellia japonica, cytoskeleton, Lilium longiflorum, pollen, pollen tube, tropism.
机译：植物的受精取决于花粉粒中的精子细胞通过花粉管到达胚珠的传递。花粉管是高度各向异性的，快速生长的细胞突起。由于花粉管不是自养的，因此需要稳定供应雌蕊提供的碳水化合物和矿物质以维持其生长。这些元素用于细胞壁材料的合成，传递到分泌小泡中的细胞壁组装位点，沿着分泌肌动蛋白的细胞骨架运输并沉积在管的生长顶点。该管必须抵抗外部变形力以保持其圆柱形状并响应各种方向信号以达到其目标。我的目标是确定细胞骨架在花粉管各向异性生长中的作用，并确定该管如何响应方向提示。花粉管中的细胞骨架由微丝和微管组成，均形成长丝状元件。对于体外生长的花粉管，必须将碳水化合物和生长矿物质以特定的量添加到生长培养基中，以维持花粉管的生长。我优化了拟南芥和山茶花粉管的生长条件，除了长百合的花粉外，它们还用作我实验的模型物种。我开发了一种基于微波的，快速有效的花粉管固定和标记方案。我使用药理，机械，分子和微观工具研究了细胞骨架在花粉管生长和向性中的作用。我发现肌动蛋白的细胞骨架，尤其是根尖下的肌动蛋白边缘，通过分泌性囊泡向生长中的顶点的受控输送，在花粉管的生长和结构调节中起着重要作用。我建造了一个变电室，可以将其安装在倒置显微镜上，以诱发受控的热带触发器。我发现肌动蛋白的细胞骨架也参与花粉管改变其方向的能力。已证明这种热带行为取决于生长培养基中钙离子的浓度和钙通过钙通道的流入。花粉管中的胞质钙梯度调节负责重塑肌动蛋白细胞骨架的各种肌动蛋白结合蛋白的活性。在这些蛋白质中，有两个我用两个固有的荧光蛋白质标记的拟南芥配子体特异性肌动蛋白解聚因子（ADF）。我发现ADF7和ADF10在微孢子发生，花粉管萌发和生长过程中差异表达，并且它们之间可能有重要的分工。关键词：肌动蛋白，肌动蛋白解聚因子，拟南芥，钙，山茶，细胞骨架，长寿百合，花粉，花粉管，向性。

著录项

  • 作者

    Bou Daher, Firas.;

  • 作者单位

    Universite de Montreal (Canada).;

  • 授予单位 Universite de Montreal (Canada).;
  • 学科 Biology Cell.
  • 学位 Ph.D.
  • 年度 2011
  • 页码 230 p.
  • 总页数 230
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 肿瘤学;
  • 关键词

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