Regulation of organ straightening and plant posture by an actin;myosin XI cytoskeleton
Regulation of organ straightening and plant posture by an actin;myosin XI cytoskeleton
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肌动蛋白 XI 细胞骨架对器官伸直和植物姿势的调节
DOI：
10.1038/nplants.2015.61
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发表时间：
2015
期刊：
影响因子：
18
通讯作者：
Miyo Terao Morita & Ikuko Hara-Nishimura
中科院分区：
文献类型：
--
作者：
Keishi Okamoto;Haruko Ueda;Tomoo Shimada;Kentaro Tamura;Takehide Kato;Masao Tasaka;Miyo Terao Morita & Ikuko Hara-Nishimura
植物能够弯曲几乎每个器官以响应重力和光等环境刺激 1, 2。在第一阶段之后，对刺激的反应受到独立机制的抑制，甚至逆转，从而使器官停止弯曲并达到所需的姿势。这种器官伸直的现象被称为自向性 3 和自动伸直 4，并建模为本体感觉 5。然而，驱动器官伸直的机制及其发生的位置大多未知。在这里，我们发现花序茎的伸直是由专门的未成熟纤维细胞中的肌动蛋白-肌球蛋白 XI 细胞骨架调节的，这些纤维细胞与茎平行并将其包围在一条细带中。肌球蛋白 XI（特别是 XIf 和 XIk）或 ACTIN8 缺陷的拟南芥突变体表现出茎响应重力而过度弯曲，这种效应与芽的物理特性无关。肌动蛋白-肌球蛋白 XI 细胞骨架使器官能够比环境刺激中一系列不断减少的超调更快地达到新位置。我们提出，伸长纤维细胞中的长肌动蛋白丝充当弯曲张力传感器，以感知器官的姿势并触发伸直系统。
Plants are able to bend nearly every organ in response to environmental stimuli such as gravity and light 1, 2. After this first phase, the responses to stimuli are restrained by an independent mechanism, or even reversed, so that the organ will stop bending and attain its desired posture. This phenomenon of organ straightening has been called autotropism 3 and autostraightening 4 and modelled as proprioception 5. However, the machinery that drives organ straightening and where it occurs are mostly unknown. Here, we show that the straightening of inflorescence stems is regulated by an actin–myosin XI cytoskeleton in specialized immature fibre cells that are parallel to the stem and encircle it in a thin band. Arabidopsis mutants defective in myosin XI (specifically XIf and XIk) or ACTIN8 exhibit hyperbending of stems in response to gravity, an effect independent of the physical properties of the shoots. The actin–myosin XI cytoskeleton enables organs to attain their new position more rapidly than would an oscillating series of diminishing overshoots in environmental stimuli. We propose that the long actin filaments in elongating fibre cells act as a bending tensile sensor to perceive the organ's posture and trigger the straightening system.