The Role of the Actin Cytoskeleton in Regulation of Auxin Transport

9318250 mudday本实验室最近的证据表明，西葫芦生长素外流载体的调节或抑制结合亚基与肌动蛋白细胞骨架有关。近年来，肌动蛋白细胞骨架的作用已被证明不仅仅是结构上的。这种丝状网络在多种生物体的细胞内运动、极性发育和细胞信号整合中起作用。尽管迄今为止对肌动蛋白细胞骨架在高等植物生长发育中的作用的研究还很有限，但肌动蛋白微丝在褐藻（Fucus）的环境控制极性发育中的作用已经得到了很好的描述。肌动蛋白细胞骨架的变化可能在开花植物的发育和环境反应中起着同样重要的作用。植物细胞骨架是唯一适合作为信号换能器从膜和细胞外基质，感知外部事件，生长素运输流允许响应这些信号。本实验旨在验证生长素极性转运是由生长素外排载体的调控蛋白与细胞骨架的相互作用所调控的新假说。为了了解生长素转运调控的本质，生长素外排载体的抑制剂或邻苯二甲酸（napthylphthalamic acid， NPA）结合蛋白与肌动蛋白之间的相互作用必须进一步研究。利用分子探针和基本的生化方法，研究了NPA结合蛋白与肌动蛋白细胞骨架在极性发育过程中的相互作用。这些实验将使用Fucus作为简化的模型系统进行。尽管达尔文提出植物极性激素运输的重要性已经有一百多年了，但生长素运输的调节机制仍然不清楚。生长素的极性和运输量在细胞外排部位受到控制。已经确定了一种调节蛋白，它结合了生长素运输的特定抑制剂，作用于生长素外排的部位。这种抑制剂结合蛋白的表征及其控制生长素运输的机制是解剖生长素运输调控途径的关键的第一步。* * *

9318250 Muday Recent evidence from this laboratory indicates that the regulatory or inhibitor binding subunit of the auxin efflux carrier from zucchini is associated with the actin cytoskeleton. In recent years, the role of the actin cytoskeleton has been shown to be more than structural. This filamentous network functions in intracellular movement, polarity development, and integration of cellular signals in a variety of organisms. Although the role of the actin cytoskeleton in the growth and development of higher plants has so far received limited study, the role of actin microfilaments in the environmentally controlled development of polarity of the brown alga, Fucus, has been elegantly described. It is likely that changes in the actin cytoskeleton play equally important roles in the development and environmental responses of flowering plants. The plant cytoskeleton is uniquely suited to act as the signal transducer from the membrane and extracellular matrix, which sense external events, to the auxin transport stream which allows response to these signals. The experiments in this proposal are designed to test the new hypothesis that polar auxin transport is regulated by interactions of the regulatory protein of the auxin efflux carrier with the cytoskeleton. In order to understand the nature of the regulation of auxin transport, the interaction between the inhibitor or napthylphthalamic acid (NPA) binding protein of the auxin efflux carrier and actin must be further delineated. Using molecular probes and basic biochemical approaches, the interactions between the NPA binding protein and the actin cytoskeleton during polar development will be examined. These experiments will be performed using Fucus as a simplified model system. Although it has been more than one hundred years since Darwin suggested the importance of polar hormone transport in plants, the mechanisms by which auxin transport is regulated still remain unclear. The polarity a nd quantity of auxin transported are controlled at the site of auxin efflux from cells. A regulatory protein has been identified which binds specific inhibitors of auxin transport that act at the site of auxin efflux. Characterization of this inhibitor binding protein, and the mechanisms by which it controls auxin transport, is the critical first step in the dissection of the regulatory pathway of auxin transport. ***