Cell wall mechanics: Some new twists
Cell wall mechanics: Some new twists
复制标题
细胞壁力学：一些新的变化
DOI：
10.1016/j.bpj.2022.02.017
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发表时间：
2022
影响因子：
3.4
通讯作者：
Cook, Douglas D.
中科院分区：
文献类型：
--
作者：
Weizbauer, Renate A.;Cook, Douglas D.
每个植物细胞都被细胞壁包围，细胞壁是一个复杂的动态系统，主要由复杂的碳水化合物和蛋白质组成，控制着细胞的形状和大小。已知这些墙在空间尺度上的成分和结构不均匀，并且墙组件和墙力学之间的关系尚不清楚。在细胞扩张过程中，细胞壁的材料特性，特别是主要承重壁成分纤维素微纤维（CMF）的方向，被认为是细胞扩张程度和方向的有力预测因素。在“干燥过程中的细胞扭曲揭示细胞壁组织中的轴向不对称性”一文中，Keynia 等人 (1) 对此模型进行了扭曲，使用毛状体分支作为模型系统来揭示一些令人着迷的生物物理学。毛状体是叶子表面形状独特、通常分枝的单细胞，对于植物与环境的接触非常重要。成熟的毛状体分支在干燥后经常表现出主要的左旋扭曲，这是一个意想不到的发现，因为膨压下的毛状体分支几何形状是轴对称的。为了确定可能在毛状分支壁力学中驱动这种手性的壁材料特性和组织，Keynia 等人 (1) 开发了一个有限元模型来复制观察到的分支行为，并得出结论，扭曲的方向和程度主要取决于 CMF 的方向。然后，为了通过实验近似 CMF 组织，他们量化了皮质微管（一种在生物合成过程中引导纤维素生物合成机器轨迹的网络）的方向，并在成熟的毛状体分支中发现了类似的主要左旋性。他们最终提出了一种基于沿分支的轴向和弯曲刚度在分支伸长过程中 CMF 取向如何变化的机制，以解释随着膨胀压力的变化从轴对称到手性分支几何形状的转变。受到 Keynia 等人文章的启发(1)，我们提出了这样的问题：“需要什么类型的实验和计算方法才能将我们对这些系统的理解提升到一个新的水平？”本文为这个问题提供了两个可能的答案：1) 开发新的实验工具以实现细胞壁内碳水化合物的可视化，2) 更广泛地采用基于群体的建模技术。
Every plant cell is surrounded by a cell wall, a complex, dynamic system composed mainly of complex carbohydrates and proteins, that governs cell shape and size. These walls are known to be nonuniform in composition and structure across spatial scales, and the relationship between wall components and wall mechanics is not well understood. During cell expansion, the material properties of the wall, particularly the orientation of the main load-bearing wall component, cellulose microfibrils (CMFs), are thought to be a strong predictor of how much and in what direction cells expand. In ‘‘Cell twisting during desiccation reveals axial asymmetry in wall organization,’’Keynia et al.(1) add a twist to this model, using trichome branches as a model system to reveal some fascinating biophysics. Trichomes, uniquely shaped, often branched, single cells on the surface of leaves are important for the plant to engage with its environment. Mature trichome branches frequently display a predominant left-handed twist after desiccation, an unexpected finding since the trichome branch geometry under turgor pressure is axisymmetric. To determine wall material properties and organization that might drive this chirality in trichome branch wall mechanics, Keynia et al.(1) developed a finite element model to replicate the observed branch behavior and concluded that direction and degree of the twist depended primarily on the orientation of CMFs. To then experimentally approximate CMF organization, they quantified orientation of cortical microtubules, a network that guides the trajectory of the cellulose biosynthetic machinery during biosynthesis, and discovered a similar predominant left-handedness in mature trichome branches. They finally propose a mechanism for how CMF orientation may shift during branch elongation, based on axial and bending stiffness along the branch, to explain the transition from an axisymmetric to chiral branch geometry with changing turgor pressure. Inspired by the article by Keynia et al.(1), we asked the question,‘‘What types of experimental and computational approaches are needed to bring our understanding of these systems to the next level?’’This article provides two possible answers to this question: 1) the development of new experimental tools to enable visualization of carbohydrates within the cell wall, and 2) a wider adoption of population-based modeling techniques.