Spatio-Temporal Regulation of Tip Growth in Pollen Tubes

智力上的优点。 该项目的重点是控制显花植物的花粉管生长。 花粉管的生长在植物的发育过程中占有重要的地位，因为它将精细胞运送到卵器中进行受精。 因此，这一过程对于有性生殖和食物生产至关重要，因为我们吃的水果、坚果、种子和谷物的发育需要一个预先的受精事件。 成功的输卵管生长和精子输送只能发生在尖端的扩张，由高膨压驱动，并通过沉积新的壁材料不断平衡。 一个重要的观察结果是发现生长速率和潜在的生理过程是振荡的，这使得有可能确定哪些过程导致生长速率的增加，哪些过程跟随生长速率的增加。 最终目标是阐明调节细胞壁扩张的机制。 似乎特别重要的过程包括分泌新的壁物质，线粒体产生能量，肌动蛋白组织，钙离子流入和pH值的变化。虽然有可能是一个单一的过程作为唯一的起搏器，它似乎更有可能是振荡行为是一个新兴的性质依赖于许多不同的过程的相互作用。因此，将采用多方面的方法来确定并行事件如何相互作用。 首先，在生长再取向过程中，将探讨上述五个过程。 我们的目标是确定哪个过程首先开始，以及它在细胞中的何处变得明显。 为了干扰花粉管生长，将使用内源性趋化因子、施加的离子梯度和升高的浓度。将包括细胞质组分和细胞形状的结构分析。 其次，将检查能量代谢，特别是烟酰胺腺嘌呤二核苷酸磷酸（NAD（P）H）的氧化/还原，并评估其对生长的影响。与抑制剂和细胞外氧选择性电极的配套研究将进一步探讨能量代谢的特点。 第三，将检查钙在线粒体能量代谢中的作用。 由于一些NAD（P）H脱氢酶是钙敏感的，因此将探索线粒体钙、细胞溶质钙和NAD（P）H之间的相互关系。 知识价值来自于研究阐明有助于控制花粉管生长的结构和生理过程的能力。 这项研究利用了花粉管在体外生长的可及性，生长事件的顶端位置，以及生长速率和基本生理过程的振荡性质。 它进一步利用广泛的遗传和荧光探针工具包，高分辨率成像和微电极技术来破译相互作用事件之间的因果关系。虽然花粉管专门用于传递精细胞，但它与其他尖端生长细胞（特别是根毛）以及扩散生长的植物细胞共享机制。 因此，从本研究中获得的信息将具有广泛的意义。更广泛的影响。 研究活动的广泛影响在很大程度上来自其重要的教育组成部分。 首席研究员有丰富的指导学生的经验。 此外，他与美国东北部10所大学组成的联盟保持密切联系，该联盟参与招募和保留代表性不足的少数民族进入研究生教育。 共同首席研究员在促进科学教育与内城学校的学生，本科生和研究生，以及中学教师广泛工作。 目前，他指导几名本科生进行荣誉研究。 最后，调查人员还调查了附近汉普郡学院的一批有研究动机的本科生，包括鲍德温学者计划中代表性不足的少数民族。 通过这些不同的途径，来自所有种族的感兴趣的本科生将被鼓励参与研究/发现过程。

Intellectual merit. This project focuses on the control of pollen tube growth in flowering plants. Pollen tube growth, which is confined to the extreme apex of the tube and is fast, occupies a crucial position in plant development because it delivers the sperm cells to the egg apparatus for fertilization. The process thus is essential for sexual reproduction and also for food production because the development of the fruits, nuts, seeds and grains that we eat requires a prior fertilization event. Successful tube growth and sperm delivery can only occur if expansion at the tip, driven by high turgor pressure, is continuously balanced by deposition of new wall materials. An important observation has been the discovery that the growth rate and the underlying physiological processes oscillate, making it possible to determine which processes lead and which follow the increase in growth rate. The ultimate goal is to elucidate the mechanisms that regulate cell wall expansion. The processes that seem particularly important include secretion of new wall material, mitochondrial production of energy, actin organization, calcium influx, and pH changes. Although it is possible that a single process acts as the sole pacemaker, it seems more likely that the oscillatory behavior is an emergent property dependent on the interaction of many different processes. As a consequence a multifaceted approach will be employed to determine how parallel events interact. Firstly, the above five processes will be probed during growth reorientation. The goal is to determine which process begins first, and where in the cell it becomes evident. To perturb pollen tube growth endogenous chemotropic factors, imposed ion gradients, and elevated osmoticum will be used. A structural analysis of cytoplasmic components and cell shape will be included. Secondly, energy metabolism, specifically the oxidation/reduction of nicotinamide adenine dinucleotide phosphate (NAD(P)H), will be examined, and its effect on growth assessed. Companion studies with inhibitors and with an extracellular oxygen-selective electrode will further probe the characteristics of energy metabolism. Thirdly, the role of calcium in mitochondrial energy metabolism will be examined. Because some NAD(P)H dehydrogenases are calcium sensitive, the inter-relationship between mitochondrial calcium, cytosolic calcium, and NAD(P)H will be explored. Intellectual merit accrues from the ability of the research to elucidate structures and physiological processes that contribute to the control of pollen tube growth. The research takes advantage of the accessibility of pollen tube growth in vitro, the apical location of the growth events, and the oscillatory nature of the growth rate and underlying physiological processes. It further exploits the extensive toolkit of genetic and fluorescent probes, high resolution imaging and microelectrode techniques to decipher cause and effect relationships between interacting events. Although the pollen tube is specialized for the delivery of sperm cells, it shares mechanisms with other tip-growing cells, notably root hairs, and also very likely with diffusely growing plant cells. Information gained from this study will therefore have wide reaching relevance. Broader impacts. The broader impacts of the research activity derive in large part from its significant educational components. The Principal Investigator has had extensive experience guiding students. In addition, he holds a close connection to a consortium of 10 universities in the northeast US involved in the recruitment and retention of under-represented minorities into graduate education. The co-Principal Investigator has worked extensively in promoting science education with inner city school students, undergraduate and graduate students, and middle school teachers. He currently directs several undergraduates in honors research. Finally, the investigators have involved a pool of research motivated undergraduates at nearby Hampshire College, including under-represented minorities in their Baldwin Scholars Program. Through these different avenues, interested undergraduate students from all ethnicities will be encouraged to participate in the research/discovery process.