Mechanical Regulation of Auxin-Mediated Growth
Mechanical Regulation of Auxin-Mediated Growth
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DOI：
10.1016/j.cub.2012.06.050
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发表时间：
2012-08-21
期刊：
影响因子：
9.2
通讯作者：
Kuhlemeier, Cris
中科院分区：
文献类型：
--
作者：
Nakayama, Naomi;Smith, Richard S.;Kuhlemeier, Cris
背景：植物激素生长素是植物生长和发育模式形成的主要调节剂。生长素在特定部位（例如器官原基）积累并诱导组织内的局部生长。生长素还介导对内在和外在物理刺激的发育反应；然而，力学究竟如何影响生长素的分布尚不清楚。结果：在这里，我们表明机械应变可以调节生长素在番茄芽尖的运输和积累，新叶在此处出现并快速生长。改变膨压、施加外力和人工生长诱导共同表明生长素外排载体 PIN1 的数量和细胞内定位对机械变化敏感。一般来说，组织的张力越大，每个细胞中存在的 PIN1 就越多，且定位于质膜的比例也越高。仅调节膜特性就足以解释大部分机械效应。结论：我们的实验支持这样的假设：质膜充当组织力学传感器，将细胞壁应变转化为细胞反应，例如膜嵌入蛋白的细胞内定位。这一基本机制的一个含义是生长素介导的年轻器官原基生长的机械增强。我们提出，生长诱导的机械应变上调 PIN1 功能和生长素积累，从而在强大的正反馈循环中促进进一步生长。
Background: The phytohormone auxin is a primary regulator of growth and developmental pattern formation in plants. Auxin accumulates at specific sites (e.g., organ primordia) and induces localized growth within a tissue. Auxin also mediates developmental responses to intrinsic and external physical stimuli; however, exactly how mechanics influences auxin distribution is unknown.Results: Here we show that mechanical strain can regulate auxin transport and accumulation in the tomato shoot apex, where new leaves emerge and rapidly grow. Modification of turgor pressure, application of external force, and artificial growth induction collectively show that the amount and intracellular localization of the auxin efflux carrier PIN1 are sensitive to mechanical alterations. In general, the more strained the tissue was, the more PIN1 was present per cell and the higher the proportion localized to the plasma membrane. Modulation of the membrane properties alone was sufficient to explain most of the mechanical effects.Conclusions: Our experiments support the hypothesis that the plasma membrane acts as a sensor of tissue mechanics that translates the cell wall strain into cellular responses, such as the intracellular localization of membrane-embedded proteins. One implication of this fundamental mechanism is the mechanical enhancement of auxin-mediated growth in young organ primordia. We propose that growth-induced mechanical strain upregulates PIN1 function and auxin accumulation, thereby promoting further growth, in a robust positive feedback loop.