Mechano-chemical basis of cellular architecture in plants

发育生物学的核心问题之一是了解生长如何导致细胞、器官和有机体的形成。这一形态发生过程除了受遗传和激素的控制外，还受到力学定律的影响，而力学定律在植物中的作用才刚刚开始被探索。由于植物细胞是不可移动的，它们需要一个强大的机制，使它们能够感知环境中的动态变化，从而产生和维持复杂的细胞和组织结构。最近的研究表明，机械信号确实是这一形态发生过程中的一个基本因素。细胞的膨胀驱动生长、细胞形状控制和细胞对负荷的反应主要由细胞壁的存在决定，细胞壁是一种坚硬但具有延展性的复合材料，主要由高度组织化的纤维素微原纤维组成。由于纤维素微纤维的合成受微管细胞骨架的调控，因此了解微管动力学及其与力学的耦合是植物形态发生的基础。在子叶多极表皮铺装细胞中，机械应力在亚细胞和组织尺度上引导微管组织。在这个项目中，我们采用跨学科的方法，包括细胞、分子、计算和生物力学技术，目的是研究生物化学和机械输入如何调节植物细胞形态发生的各个方面。我们将评估纤维素合成蛋白质的行为和微管细胞骨架在亚细胞和组织尺度上的动态在叶表皮细胞的发育时期。通过微机械操作、突变分析和计算建模，我们将探索来自周围环境的机械信号如何与微管动力学和细胞壁生物合成耦合，从而产生控制细胞形状的超细胞反馈回路。使用类似的方法，我们将确定在植物中机械传感和反应所必需的微管主调节器。实验结果将使用计算工具进行比较和测试，这些计算工具将首先用于模拟复杂表面上的微管动力学，其次用于预测组织（应力-应变）对机械扰动的局部响应。拟议的项目将使我们能够全面了解物理力对植物中纤维素生物合成和微管调节的影响，并为预测和指导未来植物组织的形态发生开辟机会。

One of the central questions in developmental biology is to understand how growth leads to the form of cells, organs and organisms. This process of morphogenesis, in addition to being under genetic and hormonal control, is also known to be influenced by the laws of mechanics, the role of which is only starting to be explored in plants. As plant cells are immobile, they require a robust machinery enabling them to sense dynamic changes in their environment allowing them to generate and maintain complex cell and tissue architectures. Recent work suggests that indeed mechanical signaling is a fundamental factor in this process of morphogenesis. Turgor driven growth of cells, cell shape control and the response of cells to load is dominated by the presence of the cell-wall, a stiff yet malleable composite mainly consisting of highly organized cellulose microfibrils. As cellulose microfibril synthesis is regulated by the microtubule cytoskeleton an understanding of microtubule dynamics, and how it couples to mechanics, is fundamental to plant morphogenesis. Previously we have shown that mechanical stress guides microtubule organization at subcellular and tissue scales in the multipolar epidermal pavement cells of cotyledons. Using interdisciplinary approaches involving cellular, molecular, computational and biomechanical techniques we aim, in this project, to investigate how biochemical and mechanical inputs regulate aspects of cellular morphogenesis in plants. We will assess the behavior of cellulose synthesizing proteins and the dynamics of the microtubule cytoskeleton at subcellular and tissue scales over developmental time periods in leaf epidermal cells. By means of micromechanical manipulation, mutant analysis and computational modeling we will explore how mechanical signals arising from the surrounding environment, couple to microtubule dynamics and cell-wall biosynthesis giving rise to a supra-cellular feedback loop that controls cell shape. Using similar approaches we will identify microtubule master regulators that are necessary for mechano-sensing and response in plants. The experimental results will be compared and tested using computational tools that will be developed to firstly model the dynamics of microtubules confined to complex surfaces, and secondly to predict the local response of tissues (stress-strain) to mechanical perturbations. The proposed project will allow us to develop a comprehensive understanding of the impact of physical forces on cellulose biosynthesis and microtubule regulation in plants and open up opportunities to not only predict but also to direct morphogenesis of plant-tissues in the future.