拟南芥fimbrin5调控花粉管生长的细胞学基础和生化机制分析

Pollen tube growth is an important step during flowering plant reproduction, which is responsible for the delivery of two non-motile sperm cells for the purpose of double fertilization. Various factors are involved in regulating pollen tube growth, among which, the actin cytoskeleton is an essential regulator via coordinating various physiological cellular processes during pollen tube growth. It remains a fundamental question regarding how pollen tube controls the organization and dynamics of the actin cytoskeleton in the field of plant cell biology. Dissection of the functions and mechanisms of action of various actin-binding proteins is the key research topic. Our previous studies found that the actin crosslinking/bundling factor Arabidopsis fimbrin5 (FIM5) regulates the organization of the actin cytoskeleton that is required for the normal pollen tube growth. However, how exactly FIM5 regulates actin dynamics in the pollen tube remains to be further explored. This project aims to elucidate the detailed molecular mechanisms underlying the regulation of actin assembly and spatial organization by FIM5. The studies include how FIM5 regulates the construction of distinct actin structures within different regions of the pollen tube, how FIM5 coordinates with other FIMBRIN isovariants or actin-binding proteins to regulate the dynamic assembly of the actin cytoskeleton, as well as how the activity of FIM5 is regulated, etc. This study will enrich our knowledge of the mechanism of action of FIM5 as well as the function and mechanism of action of the actin cytoskeleton during pollen tube growth in general.

花粉管生长是开花植物有性生殖过程的一个重要步骤,负责把两个不能运动的精细胞运输到胚囊以完成植物的双受精过程。微丝骨架通过协调各种细胞生理学过程在花粉管生长过程中发挥关键的调控作用。花粉管如何对微丝的空间组织和动态进行严格调控是植物细胞生物学领域的核心问题。对微丝结合蛋白的功能和作用机制进行解析是其中的关键研究内容。申请人实验室前期的研究发现微丝成束因子拟南芥fimbrin5（FIM5）调控微丝组织和花粉管生长，但FIM5如何在花粉管中发挥功能还不是很清楚。本项目拟综合生化、活体成像和分子遗传学等方法深入解析FIM5在花粉管中的作用机制。主要研究内容包括阐明FIM5如何在花粉管不同区域发挥功能、如何与其异构体以及其它微丝成束因子协作以及其活性调控机制的探索等。这些工作的开展将加深理解FIM5的作用机制以及微丝骨架调控花粉管生长的分子机理。

本项目的主要研究内容是解析拟南芥FIM5调控花粉管生长的生化和细胞生物学机制。发现FIM5和fimbrin家族的其它成员相比在微丝高级结构的产生和维持的功能上存在差异，并且发现其在维持花粉管亚顶端微丝结构上具有其它家族成员不可替代的功能；进一步发现FIM5的功能特异性主要存在于其氨基末端和CH2结构域，这为理解fimbrin蛋白家族以及含有CH结构域的蛋白家族在调控微丝动态组装的生化机制上具有普遍的科学理论意义。本项目还发现FIM5和PLIM蛋白协作调控微丝高级结构的产生，它们各自产生的微丝结构不同，具有特定的物理和生化特性，且两者相互竞争和微丝结合，这些结果表明这些微丝成束因子在体内必须维持一定的平衡，对于理解胞内微丝高级结构的产生和维持机制具有普遍的科学理论意义。由于该项目以花粉管为细胞学系统，相关知识的获得对于理解植物有性生殖调控机制具有重要的科学理论意义，并为农业生产实践中遗传操作作物的有性生殖提供一定的理论依据。