Function of ABP195 member of a new small 'superfamily' of plant actin binding proteins; involvement in actin organisation and signalling

植物是久坐不动的，为了生存，它们必须对独特的环境和发育信号做出反应。肌动蛋白细胞骨架对生命至关重要，它对刺激有反应，并进行重组，使细胞能够分裂和扩张，产生细胞器运动，使细胞生长极化并使细胞壁增厚；健康植物发育所需的事件，即增殖和生长、最大限度地产生能量、吸收养分、管理蒸腾流、繁殖和防止病原体入侵。为了发挥这些作用，肌动蛋白网络必须能够响应信号并重组，这些过程由肌动蛋白相关蛋白协调，这些蛋白锚定、交联或以其他方式调节该网络。凭借其独特的能力，肌动蛋白细胞骨架已经适应了植物的特定功能，通过(1)调整其相关蛋白质的功能，这些蛋白质是动物、真菌和植物所共有的，以达到自己的目的；从我的实验室和其他人的工作中，有大量的证据可以证明这一点。(2)一组植物特异性相关蛋白的进化，这些蛋白在肌动蛋白网络上的功能是植物所独有的。这个研究项目涉及一类(2)的蛋白质家族。我们在植物中发现了一类新的肌动蛋白结合蛋白的第一个迹象来自于对植物细胞内不同区室的蛋白质的筛选。这项筛选是由Oparka和同事（爱丁堡大学）进行的，它揭示了许多新的蛋白质定位于室室，如高尔基体、线粒体、细胞核、质体和细胞骨架。我们已经证明，作为该计划的支持数据，其中一种定位于细胞骨架的蛋白质定位于肌动蛋白丝。在氨基末端区域的肌动蛋白结合区域的鉴定使我们能够鉴定出具有相同结构域的其他14种蛋白质，但这15种蛋白质可以根据其羧基末端序列分为5组。这与已知的肌动蛋白结合蛋白“超家族”的情况没有什么不同，其中一个共同的肌动蛋白结合域附着在独特的序列上，这个独特的序列指定了它在细胞中对肌动蛋白的作用。我们在这里提供的初步数据加上对现有数据库数据的利用表明，该超家族的一个成员参与了质膜上肌动蛋白网络的组织，一个成员对正常植物发育至关重要。本研究的目的是了解这两种蛋白在植物发育过程中如何促进肌动蛋白细胞骨架的正常功能。

Plants are sedentary and have to respond to unique environmental and developmental signals in order to survive. The actin cytoskeleton is essential for life, is stimulus responsive and reorganises so that cells can divide and expand, generate organelle movement, polarise cell growth and thicken the cell wall; events that are required for healthy plant development i.e. for proliferation and growth, for maximising energy production, for the uptake of nutrients, for managing the transpiration stream, for reproduction and for protection against pathogen invasion. In order to perform these roles the actin network has to be able to respond to signals and reorganise, processes that are coordinated by actin associated proteins that anchor, crosslink or otherwise regulate this network. With its unique capabilities the actin cytoskeleton has become adapted to plant specific function by (1) tuning the function of its associated proteins, common to animals, fungae and plants, for its own purposes; there is a wealth of evidence of this from work in my lab and others and (2) the evolution of a set of plant specific associated proteins whose function on the actin network is unique to plants. This programme of research concerns a family of proteins that fit into category (2). The first indication that we had a new class of actin binding proteins in plants came from a screen for proteins localising to different compartments within a plant cell. This screen was performed by Oparka and colleagues (University of Edinburgh) and it revealed many new proteins locating to compartments such as Golgi, mitochondria, nucleus, plastids and the cytoskeleton. We have shown, as supporting data for this programme, that one of the proteins localising to the cytoskeleton localised to actin filaments. Identification of the actin binding domain in the amino -terminal region allowed us to identify 14 other proteins having the same domain but that the 15 proteins could be divided into 5 groups based on there carboxy-terminal sequence. This is not unlike the situation for known 'Superfamilies' of actin binding proteins where a common actin binding domain is attached to unique sequence and this unique sequence specifies its role with respect to actin in the cell. Preliminary data we present here plus utilisation of data from current databases suggest that one member of this superfamily is involved with the organisation of the actin network at the plasma membrane and one member is essential for normal plant development. The goal of this research is to understand how these two proteins contribute to the normal function of the actin cytoskeleton in plant development.