Pollen apertures as a model for formation of distinct extracellular domains

在生物体中，细胞外物质沉积在细胞旁边可以保护细胞，改变细胞的生长和形态，或帮助细胞移动和与其他细胞沟通。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，但细胞如何实现这种精确大多是未知的。细胞外结构具有非常精确的沉积的一个美丽的例子是植物花粉周围的墙壁。不同物种的花粉颗粒通常看起来非常不同，部分原因是壁物质沉积在花粉表面的一些地方，而其他地方没有。没有花粉壁的地方被称为孔道，这些结构帮助花粉发挥其生殖功能。不同物种的花粉孔在形状、数量和位置上往往不同，但在同一物种内，花粉孔图案通常是相同的。以花粉孔的形成为模型，这个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，以及这些区域的位置是如何标记的。理解花粉背景下的模式形成将有助于洞察许多发育过程中的模式形成。在这个项目的更广泛的影响中，几位年轻的科学家将接受培训，工作结果将通过文理本科课程的讲座、显微镜课程，以及在生物增强研讨会和Capstone实习计划中与初中生互动来向更多的受众传播。细胞如何形成精确定义的细胞外结构域是一个重要而鲜为人知的问题。花粉粒为研究这一问题提供了一个很好的模型，因为它们的表面被细胞壁覆盖，外壁组装成不同物种特有的模式。这道墙保护花粉粒内的精子细胞，并在植物繁殖中发挥其他几个重要作用。除了外壁覆盖的区域外，大多数植物的花粉表面都有特有的开口或孔，其中没有外壁或外壁减少。这表明，在花粉发育过程中，在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不同于其他表面的结构域，并将成为孔道。就像外壁模式的情况一样，不同物种的气孔往往有很大的差异，在数量、位置和形态上都不同，但在每个物种内部，它们的模式都受到严格的发育控制。由于定义明确、调节严格、易于识别和量化的结构，气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句柄，并可以作为一个强大的模型来产生不同的胞外域，这是一个在各种细胞和生物体中非常重要的过程。通过各种遗传、细胞生物学和计算方法，并以拟南芥花粉为模型，该项目旨在辨别孔指定结构域是如何形成的，并确定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上不同的外围域，以及细胞壁沉积机制如何解释这些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.