A transmembrane formin nucleates subapical actin assembly and controls tip-focused growth in pollen tubes
A transmembrane formin nucleates subapical actin assembly and controls tip-focused growth in pollen tubes
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DOI：
10.1073/pnas.1008527107
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发表时间：
2010-09-14
影响因子：
11.1
通讯作者：
Wu, Hen-Ming
中科院分区：
文献类型：
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作者：
Cheung, Alice Y.;Niroomand, Shahriar;Wu, Hen-Ming
花粉管是高度极化的植物细胞，专门为受精提供精子。花粉管生长迅速，只发生在顶端，距离可达花粉粒直径的数千倍而不进行细胞分裂，因此是研究细胞不对称生长的极好模型系统。在开花植物中，花粉管的生长依赖于肌动蛋白细胞骨架，它支持一个有效的囊泡运输系统，将膜和细胞壁材料输送到管端。一个高度动态的顶下肌动蛋白结构和顶端囊泡区对于尖端生长过程是至关重要的。这种尖端组织是如何维持的，尖下肌动蛋白结构是如何组装的，以及它与尖端生长的功能耦合的直接证据仍有待建立。在这里，我们展示了一种位于顶端的、细胞膜锚定的肌动蛋白核蛋白，拟南芥形成同源5(FH5)，刺激来自顶端下膜的肌动蛋白组装，提供肌动蛋白细丝用于囊泡运输到顶端穹顶，并介导顶端下肌动蛋白结构的组装。此外，表达FH5的花粉管提供了一个独特的机会来证明顶下肌动蛋白结构的组装伴随着顶端的快速生长，为它们的功能耦合提供了进一步的支持。总之，我们的结果表明，FH5在建立顶端下的肌动蛋白和顶端囊泡组织方面发挥了关键作用，这些组织对于花粉管中顶端聚焦的生长至关重要。
Pollen tubes are highly polarized plant cells specialized in delivering sperm for fertilization. Pollen tube growth is rapid, occurs exclusively at the tip, and can reach distances thousands of times the diameter of the pollen grain without cell division, thus representing an excellent model system for studying asymmetric cell growth. In flowering plants, pollen tube growth is dependent on the actin cytoskeleton, which supports an efficient vesicle trafficking system to deliver membrane and cell-wall materials to the tube tip. A highly dynamic subapical actin structure and an apical vesicular zone are known to be critical for the tip-growth process. How this apical organization is maintained, how the subapical actin structure is assembled, and direct evidence for its functional coupling with tip growth remain to be established. Here, we show that a tip-located, cell membrane-anchored actin-nucleating protein, the Arabidopsis formin homology5 (FH5), stimulates actin assembly from the subapical membrane, provides actin filaments for vesicular trafficking to the apical dome, and mediates assembly of the subapical actin structure. Moreover, FH5-expressing pollen tubes provided a unique opportunity to demonstrate that assembly of the subapical actin structure is concomitant with the acquisition of rapid tip growth, providing further support for their functional coupling. Together, our results show that FH5 plays a pivotal role in establishing the subapical actin and apical vesicular organization critical for tip-focused growth in pollen tubes.