Cheung Alice Y, Wu Hen-Ming
Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Annu Rev Plant Biol. 2008;59:547-72. doi: 10.1146/annurev.arplant.59.032607.092921.
Pollen tubes elongate within the pistil to transport sperms to the female gametophytes for fertilization. Pollen tubes grow at their tips through a rapid and polarized cell growth process. This tip growth process is supported by an elaborate and dynamic actin cytoskeleton and a highly active membrane trafficking system that together provide the driving force and secretory activities needed for growth. A polarized cytoplasm with an abundance of vesicles and tip-focused Ca(2+) and H(+) concentration gradients are important for the polar cell growth process. Apical membrane-located Rho GTPases regulate Ca(2+) concentration and actin dynamics in the cytoplasm and are crucial for maintaining pollen tube polarity. Pollen tube growth is marked by periods of rapid and slow growth phases. Activities that regulate and support this tip growth process also show oscillatory fluctuations. How these activities correlate with the rapid, polar, and oscillatory pollen tube growth process is discussed.
花粉管在雌蕊内伸长，将精子运输到雌配子体进行受精。花粉管通过快速且极化的细胞生长过程在其顶端生长。这个顶端生长过程由精细且动态的肌动蛋白细胞骨架和高度活跃的膜运输系统支持，它们共同提供生长所需的驱动力和分泌活动。具有大量囊泡以及顶端聚焦的Ca(2+)和H(+)浓度梯度的极化细胞质对于极性细胞生长过程很重要。位于顶端膜的Rho GTPases调节细胞质中的Ca(2+)浓度和肌动蛋白动力学，并且对于维持花粉管极性至关重要。花粉管生长的特点是快速生长阶段和缓慢生长阶段交替出现。调节和支持这个顶端生长过程的活动也表现出振荡波动。本文讨论了这些活动如何与快速、极性和振荡的花粉管生长过程相关联。
