眾所周知，微絲細(xì)胞骨架的動態(tài)組裝控制花粉管的極性生長,。然而到目前為止,，人們對花粉管如何精密調(diào)控微絲的動態(tài)組裝還知之甚少。
中科院植物研究所黃善金研究組對花粉中高度表達(dá)的微絲相關(guān)蛋白VILLIN5進(jìn)行了功能解析,，發(fā)現(xiàn)擬南芥缺失VILLIN5之后花粉管中微絲的穩(wěn)定性迅速下降,，進(jìn)而影響花粉管生長，說明擬南芥VILLIN5很可能通過穩(wěn)定微絲調(diào)控極性生長,。
利用體外生化分析和全內(nèi)反射熒光顯微技術(shù),，研究人員發(fā)現(xiàn)，VILLIN5具有微絲成束和依賴于鈣離子的微絲切割功能,，同時還發(fā)現(xiàn)生理水平的鈣離子濃度足以激活VILLIN5的切割活性,。
該研究為植物VILLIN在細(xì)胞內(nèi)的生理學(xué)功能提供了直接證據(jù)，豐富了人們對該蛋白家族作用的理解,，暗示VILLIN5很可能通過協(xié)同鈣離子信號調(diào)控花粉管生長,。該研究成果為闡明微絲細(xì)胞骨架與植物細(xì)胞極性生長的關(guān)系，進(jìn)而建立植物細(xì)胞極性生長的調(diào)控網(wǎng)絡(luò)提供了重要的實驗證據(jù),。（生物谷Bioon.com）
生物谷推薦英文摘要：
The Plant Cell doi：10.1105/tpc.110.076257
Arabidopsis VILLIN5, an Actin Filament Bundling and Severing Protein, Is Necessary for Normal Pollen Tube Growth[W]
Hua Zhanga,b,1, Xiaolu Qua,b,1, Chanchan Baoa,b, Parul Khuranac, Qiannan Wanga,b, Yurong Xiea, Yiyan Zhenga,b, Naizhi Chena, Laurent Blanchoind, Christopher J. Staigerc and Shanjin Huanga,2
a Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
b Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
c Department of Biological Sciences and Bindley Bioscience Center, Purdue University, West Lafayette, Indiana 47907-2064
d Institut de Recherches en Technologie et Sciences pour le Vivant, Laboratoire de Physiologie Cellulaire Végétale, Commissariat à l’Energie Atomique/Centre National de la Recherche Scientifique/Université Joseph Fourier, F38054 Grenoble, France
A dynamic actin cytoskeleton is essential for pollen germination and tube growth. However, the molecular mechanisms underlying the organization and turnover of the actin cytoskeleton in pollen remain poorly understood. Villin plays a key role in the formation of higher-order structures from actin filaments and in the regulation of actin dynamics in eukaryotic cells. It belongs to the villin/gelsolin/fragmin superfamily of actin binding proteins and is composed of six gelsolin-homology domains at its core and a villin headpiece domain at its C terminus. Recently, several villin family members from plants have been shown to sever, cap, and bundle actin filaments in vitro. Here, we characterized a villin isovariant, Arabidopsis thaliana VILLIN5 (VLN5), that is highly and preferentially expressed in pollen. VLN5 loss-of-function retarded pollen tube growth and sensitized actin filaments in pollen grains and tubes to latrunculin B. In vitro biochemical analyses revealed that VLN5 is a typical member of the villin family and retains a full suite of activities, including barbed-end capping, filament bundling, and calcium-dependent severing. The severing activity was confirmed with time-lapse evanescent wave microscopy of individual actin filaments in vitro. We propose that VLN5 is a major regulator of actin filament stability and turnover that functions in concert with oscillatory calcium gradients in pollen and therefore plays an integral role in pollen germination and tube growth.
