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首页> 外文期刊>Protoplasma: An International Journal of Cell Biology >Rhizoids and protonemata of characean algae: model cells for research on polarized growth and plant gravity sensing
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Rhizoids and protonemata of characean algae: model cells for research on polarized growth and plant gravity sensing

机译：Characean藻类的根状茎和原生质体：用于极化生长和植物重力感应研究的模型细胞

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Gravitropically tip-growing rhizoids and protonemata of characean algae are well-establislied unicellular plant model systems for research on gravitropism. In recent years, considerable progress has been made in the understanding of the cellular and molecular mechanisms Underlying gravity sensing and gravity-oriented growth. While in higherplant statocytes the role of cytoskeletal elements, especially the actin cytoskeleton, in the mechanisms of gravity sensing is still enigmatic, there is clear evidence that in the characean cells actin is intimately involved in polarized growth, gravity sensing, and the gravitropic response mechanisms. The multiple functions of actin are orchestrated by a variery of actin-binding proteins which control actin polymerisation. regulate the dynamic remodelling of the actin filament architecture, and mediate the transport of vesicles and organelles. Actin and a steep gradient of cytoplasmic free calcium are crucial components of a feedback mechanism that controls polarized growth. Experiments performed in microgravity provided evidence that actomyosin is a key player for gravity sensing: it coordinates the position of statoliths and, upon a change in the cell's orientation, directs sedimenting statoliths to specific areas of the plasma membrane, where contact with membrane-bound gravisensor Molecules elicits. short gravitropic pathways. In rhizoids, gravitropic signalling leads to a local reduction of cytoplasmic free calcium and results in differential growth of the opposite subapical cell flanks. The negative gravitropic response of protonemata involves actin-dependent relocation of the calcium gradient and displacement of the centre of maximal growth towards the upper flank. On the basis of the results obtained front the gravitropic model cells, a similar fine-tuning function of the actomyosin system is discussed for the early steps of gravity sensing in higher-plant statocytes.
机译：甲虫藻的重力生长尖端和根状茎是原生植物，具有很好的单向性，可用于重力研究。近年来，在重力感应和重力定向生长基础的细胞和分子机理的理解上取得了长足的进步。尽管在高等植物的稳态细胞中，细胞骨架元件，尤其是肌动蛋白细胞骨架在重力感应机制中的作用仍然是未知的，但有明确的证据表明，在恰拉桑细胞中，肌动蛋白与极化生长，重力感应和重力反应机制密切相关。 。肌动蛋白的多种功能由控制肌动蛋白聚合的各种肌动蛋白结合蛋白来协调。调节肌动蛋白丝结构的动态重塑，并介导囊泡和细胞器的运输。肌动蛋白和陡峭的细胞质游离钙梯度是控制极化生长的反馈机制的关键组成部分。在微重力下进行的实验提供了证据，表明肌动球蛋白是重力感应的关键参与者：它能协调石笋的位置，并在细胞方向发生变化时将沉淀的石笋引导到质膜的特定区域，并与膜结合的重力传感器接触分子引出。短的重力路径。在类根瘤中，重力信号转导导致细胞质游离钙的局部减少，并导致相反的心尖下细胞侧面的差异生长。 propromatmata的负重力反应涉及钙梯度的肌动蛋白依赖性重定位和最大生长中心向上侧的位移。基于在重力模型细胞之前获得的结果，讨论了放线菌素系统的类似微调功能，用于在高等植物稳态细胞中进行重力传感的早期步骤。

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