Rapid, unidirectional pollen tube tip growth is essential for fertilization and is widely employed as a model of polar cell expansion, a process crucial for plant morphogenesis. Different proteins and lipids with key functions in the control of polar cell expansion are associated with distinct domains of the plasma membrane (PM) at the pollen tube tip. These domains need to be dynamically maintained during tip growth, which depends on massive secretory and endocytic membrane trafficking. Very little is currently known about the molecular and cellular mechanisms responsible for the compartmentalization of the pollen tube PM. To provide a reliable structural framework for the further characterization of these mechanisms, an integrated quantitative map was compiled of the relative positions in normally growing Nicotiana tabacum (tobacco) pollen tubes of PM domains 1) enriched in key signaling proteins or lipids, 2) displaying high membrane order, or 3) in contact with cytoplasmic structures playing important roles in apical membrane trafficking. Previously identified secretory and endocytic PM domains were also included into this map. Internalization of regulatory proteins or lipids associated with PM regions overlapping with the lateral endocytic domain was assessed based on brefeldin A (BFA) treatment. These analyses revealed remarkable aspects of the structural organization of tobacco pollen tube tips, which 1) enhance our understanding of cellular and regulatory processes underlying tip growth, and 2) highlight important areas of future research.

中文翻译：

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质膜和细胞质区室化：花粉管尖端生长所需的动态结构框架


快速、单向的花粉管尖端生长对于受精至关重要，并被广泛用作极性细胞扩增的模型，这是对植物形态发生至关重要的过程。在控制极性细胞扩增中具有关键功能的不同蛋白质和脂质与花粉管尖端质膜 （PM） 的不同结构域相关。这些结构域需要在尖端生长过程中动态维持，这取决于大量的分泌膜和内吞膜运输。目前对负责花粉管 PM 区室化的分子和细胞机制知之甚少。为了为进一步表征这些机制提供可靠的结构框架，编制了正常生长的烟草（烟草）花粉管中相对位置的综合定量图谱 PM 结构域 1） 富含关键信号蛋白或脂质，2） 显示高膜顺序，或 3） 与细胞质结构接触在顶端膜运输中起重要作用。先前鉴定的分泌型和内吞型 PM 结构域也包含在该图谱中。基于布雷菲德菌素 A （BFA） 处理评估与外侧内吞结构域重叠的 PM 区域相关的调节蛋白或脂质的内化。这些分析揭示了烟草花粉管尖端结构组织的显着方面，这 1） 增强了我们对尖端生长的细胞和调节过程的理解，以及 2） 突出了未来研究的重要领域。