Biology Department, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Plant Cell. 2011 Oct;23(10):3696-710. doi: 10.1105/tpc.111.090753. Epub 2011 Oct 14.
The remodeling of actin networks is required for a variety of cellular processes in eukaryotes. In plants, several actin binding proteins have been implicated in remodeling cortical actin filaments (F-actin). However, the extent to which these proteins support F-actin dynamics in planta has not been tested. Using reverse genetics, complementation analyses, and cell biological approaches, we assessed the in vivo function of two actin turnover proteins: actin interacting protein1 (AIP1) and actin depolymerizing factor (ADF). We report that AIP1 is a single-copy gene in the moss Physcomitrella patens. AIP1 knockout plants are viable but have reduced expansion of tip-growing cells. AIP1 is diffusely cytosolic and functions in a common genetic pathway with ADF to promote tip growth. Specifically, ADF can partially compensate for loss of AIP1, and AIP1 requires ADF for function. Consistent with a role in actin remodeling, AIP1 knockout lines accumulate F-actin bundles, have fewer dynamic ends, and have reduced severing frequency. Importantly, we demonstrate that AIP1 promotes and ADF is essential for cortical F-actin dynamics.
肌动蛋白网络的重构对于真核生物的各种细胞过程是必需的。在植物中，几种肌动蛋白结合蛋白已被牵连到皮质肌动蛋白丝（F-肌动蛋白）的重构中。然而，这些蛋白质在植物体内支持 F-肌动蛋白动力学的程度尚未得到检验。我们使用反向遗传学、互补分析和细胞生物学方法，评估了两种肌动蛋白周转率蛋白的体内功能：肌动蛋白相互作用蛋白 1（AIP1）和肌动蛋白解聚因子（ADF）。我们报告说，AIP1 是苔藓植物Physcomitrella patens 中的一个单拷贝基因。AIP1 敲除植物是可行的，但尖端生长细胞的扩展减少。AIP1 弥散在细胞质中，与 ADF 共同作用于促进尖端生长的遗传途径。具体来说，ADF 可以部分补偿 AIP1 的缺失，而 AIP1 则需要 ADF 来发挥功能。与肌动蛋白重构的作用一致，AIP1 敲除系积累 F-肌动蛋白束，动态末端较少，切割频率降低。重要的是，我们证明了 AIP1 促进了皮层 F-肌动蛋白的动力学，而 ADF 则是其必需的。
