Pollen-stigma interactions: events and players that set off the path to reproductive success

开花植物的授粉是受精的必要过程。种子和果实的生产、植物物种的保存和多样性的产生都依赖于授粉的成功。本项目主要研究花粉与柱头（雌蕊（雌性生殖器官）上的花粉接受面）如何相互作用以启动授粉。柱头上的第一个事件是花粉发芽，从而产生花粉管，花粉管穿过柱头并在雌蕊内伸长，将精子输送到卵子。休眠花粉粒激活的机制尚不清楚。这个过程需要花粉细胞质分布到一个小区域，在那里花粉管从谷物中伸出，生长到雌蕊中，开始一个富有成果的旅程。这个项目的重点是获得这些最早的授粉事件的分子理解。通过柱头和花粉之间的水分传递来激活花粉粒，花粉中的细胞质重组来设计管挤压和管生长过程，以及修饰花粉和柱头细胞壁以促进管挤压和管刺入雌蕊的酶，将研究它们对早期授粉事件成功的贡献。该项目将培养本科生、硕士生、博士生和研究生水平的科学家，为研究人员和未来的科学领导者提供管道。与山谷女孩公司（马萨诸塞州霍利奥克）的合作将为高中女生带来以项目研究领域为中心的暑期体验。近年来，在对开花植物生殖过程的分子和细胞理解方面取得了重要进展，特别是在带精子的花粉如何与雌蕊组织相互作用以使受精产生种子方面。重要但未被充分探索的是花粉降落在雌蕊（柱头）的受感表面时发生的最早事件，以启动授粉过程。这个项目的重点是获得对这些早期事件的分子和细胞理解。具体来说，该项目探讨了柱头乳头细胞如何从柱头中动员水分，为干燥和休眠的花粉粒补水，以激活萌发，这涉及到从花粉粒中挤出极化的产物并发育成花粉管。它还研究了花粉粒如何动员其细胞表面信号传导和细胞质成分来协调花粉管挤压和柱头穿透。在花粉和雌蕊中都发生了相当大的细胞壁降解和修饰活动，使萌发和管生长过程成为可能。因此，细胞壁降解酶如何促进这些过程也将被检查。本研究以拟南芥为模型系统，结合分子、转基因、细胞生物学和生化等方法。该项目将为本科至博士后阶段的学生提供广泛的科学知识和研究方法经验，可以广泛应用。将为邻近内城的高中生开设与植物繁殖有关的夏季讲习班。分子和细胞生物科学部的细胞动力学和功能组共同资助了该奖项。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Pollination in flowering plants is the requisite process for fertilization. The production of seeds and fruits, preservation of plant species and generating diversity all rely on pollination success. This project focuses on understanding how pollen and stigma, the pollen receptive surface on the pistil (the female reproductive organ) interact to initiate pollination. The first event on the stigma is for the pollen to germinate, thereby generating a pollen tube which penetrates the stigma and elongates inside the pistil to deliver sperm to the egg. The mechanisms underlying the activation of dormant pollen grains are poorly understood. The process requires the pollen cytoplasm to distribute to a small area where a pollen tube emerges from the grain and grows into the pistil to start a fruitful journey. This project focuses on obtaining a molecular understanding of these earliest pollination events. Water transfer between the stigma and pollen to activate the pollen grain, cytoplasmic reorganization in the pollen to engineer the tube extrusion and tube growth process, and the enzymes that modify the pollen and stigma cell walls to facilitate tube extrusion and its penetration of the pistil will be examined for their contribution to the success of the early pollination events. The project will train undergraduates, Master’s, Ph.D. students, and post-graduate level scientists, feeding the pipeline for the research workforce and future leaders in science. A collaboration with Girls Inc. of the Valley (Holyoke MA) will bring high school girls for a summer experience centered on the project research area. Important advances have been made in recent years in the molecular and cellular understanding of the reproduction process in flowering plants, especially in how the sperm-bearing pollen interact with tissues in the pistil to enable fertilization to produce seeds. Important but under-explored are the earliest events which occur upon pollen landing on the receptive surface of the pistil, the stigma, to set off the pollination process. This project focuses on obtaining a molecular and cellular understanding of these early events. Specifically, the project explores how the stigmatic papilla cells mobilize water from the stigma to hydrate a dry and dormant pollen grain to activate germination, which involves the extrusion of a polarized outgrowth from the grain and its development into a pollen tube. It also examines how the pollen grain mobilizes its cell surface signaling and cytoplasmic components to orchestrate pollen tube extrusion and penetration of the stigma. Considerable cell wall degradation and modification activities occur in both the pollen and the pistil to enable the germination and tube growth process. Therefore, how cell wall degradative enzymes contribute to these processes will also be examined. The research uses Arabidopsis as the model system and relies on combined molecular, transgenic, cell biological and biochemical approaches. The project will provide students from undergraduate to postdoctoral levels with a broad range of scientific knowledge and experience in research approaches that can be broadly applied. A summer workshop related to plant reproduction will be developed for high school students from neighboring inner cities. The Cellular Dynamics and Function cluster in the Division of Molecular and Cellular Biosciences is co-funding this award.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.