SPIRAL2 determines plant microtubule organization by modulating microtubule severing.
SPIRAL2 determines plant microtubule organization by modulating microtubule severing.
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DOI：
10.1016/j.cub.2013.07.061
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发表时间：
2013-10-07
期刊：
影响因子：
9.2
通讯作者：
Turner, Simon R.
中科院分区：
文献类型：
--
作者：
Wightman, Raymond;Chomicki, Guillaume;Kumar, Manoj;Carr, Paul;Turner, Simon R.
植物生长和形态的定义特征之一是细胞扩增的关键作用。虽然细胞壁的机械性质决定了细胞扩张的程度和方向，但皮质微管阵列在细胞壁组织中起着关键作用，因此决定了定向（各向异性）细胞扩张。微管切割酶katanin对于植物形成对齐的微管阵列是必不可少的;然而，单独增加切割活性不足以驱动微管对齐。在这里，我们证明了katanin活性取决于微管相关蛋白（MAP）SPIRAL 2（SPR 2）的行为。叶柄细胞在子叶表皮表现出良好的排列微管阵列，而相邻的路面细胞表现出不对齐的阵列，即使SPR 2被发现在这两种细胞类型的水平相似。然而，在铺面细胞中，SPR 2在微管交叉位点积累，在那里它稳定这些交叉并防止切断。相反，在相邻的叶柄细胞中，SPR 2不断地沿着微管移动，暴露出交叉位点，这些位点成为切断的底物。因此，我们的研究揭示了一种新的机制，即微管组织的动力学和定位的MAP，调节何时何地发生微管切断。SPR 2是一种多功能MAP，能够抑制基于katanin的MT切断。在具有网状微管的细胞中，SPR 2防止微管交叉处的切断。在具有良好排列的微管的细胞中，SPR 2的移动性允许微管切断。SPR 2动力学通过调节微管切断来控制微管组织。
One of the defining characteristics of plant growth and morphology is the pivotal role of cell expansion. While the mechanical properties of the cell wall determine both the extent and direction of cell expansion, the cortical microtubule array plays a critical role in cell wall organization and, consequently, determining directional (anisotropic) cell expansion. The microtubule-severing enzyme katanin is essential for plants to form aligned microtubule arrays; however, increasing severing activity alone is not sufficient to drive microtubule alignment. Here, we demonstrate that katanin activity depends upon the behavior of the microtubule-associated protein (MAP) SPIRAL2 (SPR2). Petiole cells in the cotyledon epidermis exhibit well-aligned microtubule arrays, whereas adjacent pavement cells exhibit unaligned arrays, even though SPR2 is found at similar levels in both cell types. In pavement cells, however, SPR2 accumulates at microtubule crossover sites, where it stabilizes these crossovers and prevents severing. In contrast, in the adjacent petiole cells, SPR2 is constantly moving along the microtubules, exposing crossover sites that become substrates for severing. Consequently, our study reveals a novel mechanism whereby microtubule organization is determined by dynamics and localization of a MAP that regulates where and when microtubule severing occurs. SPR2 is a multifunctional MAP that is able to inhibit katanin-based MT severing In cells with net-like microtubules, SPR2 prevents severing at microtubule crossovers In cells with well-aligned microtubules, SPR2 mobility allows microtubule severing SPR2 dynamics control microtubule organization by regulating microtubule severing
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