Pollen apertures as a model for formation of distinct extracellular domains

在生物体中，细胞外物质在细胞旁的沉积可以保护细胞，改变细胞的生长和形态，或帮助细胞移动和与其他细胞交流。为了能够执行如此重要的功能，细胞外物质必须非常精确地沉积，但是细胞是如何达到这种精度的大部分是未知的。一个非常精确沉积的胞外结构的美丽例子是植物花粉周围的壁。不同物种的花粉粒通常看起来非常不同，部分原因是花粉表面的某些地方沉积了壁物质，而其他地方则没有。没有花粉壁的地方被称为花粉孔，这些结构有助于花粉发挥其生殖功能。在不同的物种中，花粉孔的形状、数量和位置往往不同，但在一个物种内，花粉孔的模式通常是相同的。以花粉孔的形成为模型，该项目将研究细胞如何确定哪些表面区域将缺乏细胞外结构，以及如何标记这些区域的位置。在花粉的背景下了解模式的形成将有助于了解许多发育过程中的模式形成。从更广泛的影响来看，该项目将培训几名年轻科学家，并通过艺术与科学本科课程、显微镜课程的讲座，以及在生物强化研讨会和顶点实习计划期间与中学生互动，将工作成果传达给更多的受众。细胞如何发展出精确定义的胞外结构域是一个重要而又知之甚少的问题。花粉粒为研究这个问题提供了一个很好的模型，因为它们的表面覆盖着细胞壁，外壁，它们组装成不同物种特有的图案。这层细胞壁保护花粉粒内的精细胞，并在植物繁殖中起着其他几个重要作用。除了被外壁覆盖的区域外，大多数植物的花粉表面都有典型的开口或孔洞，其中没有或减少了外壁。这表明，在花粉发育过程中，花粉表面形成了特定的结构域，这些结构域被细胞壁沉积机制可靠地识别为与表面其他部分不同的结构域，并将成为孔。就像外叶模式一样，不同物种的气孔在数量、位置和形态上都有很大的不同，但在每个物种内，气孔的模式都受到严格的发育控制。作为定义明确、调控严格、易于识别和量化的结构，孔为解决花粉表面模式形成的复杂问题提供了一个有吸引力的处理方法，并且可以作为一个强大的模型来产生不同的细胞外结构域，这是一个在各种细胞和生物体中重要的过程。通过多种遗传、细胞生物学和计算方法，并以拟南芥花粉为模型，本项目旨在了解孔指定结构域是如何形成的，并定义对孔发育重要的细胞生物学事件。这将为植物细胞如何产生功能不同的外周结构域以及细胞壁沉积机制如何解释这些结构域以产生细胞外差异创造一个范例。

In an organism, deposition of extracellular materials next to a cell can protect the cell, change its growth and morphology, or help it to move and communicate with other cells. To be able to perform such important functions, extracellular materials must be deposited very precisely, but how cells achieve such precision is mostly unknown. A beautiful example of an extracellular structure with a very precise deposition is the wall surrounding plant pollen. Pollen grains from different species often look remarkably different, in part, because wall materials are deposited at some places on pollen surface and absent from the others. The places where pollen wall is absent are called apertures, and these structures help pollen perform its reproductive function. Across species, pollen apertures often differ in shape, number, and positions, but within a species aperture patterns are usually the same. Using formation of pollen apertures as a model, this project will investigate how cells determine which surface areas will lack extracellular structures and how positions of such areas are marked. Understanding pattern formation in the context of pollen will provide insight into pattern formation during many developmental processes. In broader impacts of this project, several young scientists will be trained and the results of the work will be communicated to larger audiences through lectures in an Arts & Science undergraduate course, microscopy courses, and by interacting with middle- and high-school students during biology enhancement workshops and a Capstone internship program.How cells develop precisely defined domains of extracellular structures is an important and poorly understood question. Pollen grains provide an excellent model for studying this problem, as their surfaces are covered by the cell wall, exine, which assembles into diverse species-specific patterns. This wall protects sperm cells within the pollen grains and plays several other important roles in plant reproduction. In addition to the exine-covered areas, pollen surfaces of most plant species have characteristic openings, or apertures, where exine is absent or reduced. This indicates that, in the course of pollen development, specific domains are formed on pollen surface, which are reliably recognized by the cell wall deposition machinery as different from the rest of the surface and which will become apertures. As is the case with exine patterns, apertures often vary greatly across species, differing in their number, positions, and morphology, yet within each species their patterns are under tight developmental control. As well-defined, tightly regulated, and easily recognizable and quantifiable structures, apertures provide an attractive handle for addressing the complex problems of pollen surface pattern formation and can serve as a powerful model for generation of distinct extracellular domains, a process important in a wide variety of cells and organisms. Through a variety of genetic, cell-biological, and computational methods and using Arabidopsis pollen as a model, this project aims to discern how the aperture-specifying domains are formed and to define cell-biological events important for aperture development. This will allow creating a paradigm for how plant cells generate functionally distinct peripheral domains, and how cell wall deposition machinery interprets these domains to generate extracellular differences.