Dynamic patterns of the plant growth regulator auxin

植物发育过程中最有影响力的信使是微小的生长调节剂生长素。植物激素控制细胞分裂和细胞生长等基本过程，并以枝条结构和叶片维管系统的基本模式积累。因此，生长素控制植物的动态形态。生长素及其载体PIN和AUX/LAX的模式在植物发育过程中是动态和重组的。模拟生长素模式的漫长历史最近经历了一次重置，因为直到那时神秘的PIN极性被发现很可能是由发育中的组织内产生的机械应力协调的。这一发现现在表明，生长素/PIN和组织力学之间存在以下未被探索的反馈循环。细胞中的生长素浓度高会软化相邻的细胞壁，从而在组织内产生机械应力。机械应力反过来反馈生长素流动，因为PIN结合沿着受压的细胞壁上调。正如组织力学在生长素构图中起着重要作用一样，细胞几何形状和整个组织的生物力学变化也是如此。细胞几何和生物力学变异对生长素构型有多大影响是一个悬而未决的问题。为了解决这一重要问题，我们建议通过预测来自实时成像的分割组织上的生长素构图动力学，并将模型预测与实验观察相比较，来研究细胞几何构型和生物力学变异对生长素构型的影响。特别是，我们将利用导致创始人细胞选择的生长素动态的自然变异性，以两个相邻的生长素浓度较高的细胞为标志，来确定细胞几何形状在生长素构图动态中的作用。此外，我们将使用在侧根形成过程中覆盖的内胚层的关键和众所周知的力学变化作为跨组织的生物力学变化在生长素模式形成中的作用的案例研究。这两个案例研究将与来自Maizel实验室的实验数据进行密切反馈(P6)，并将进一步允许我们探索细胞分裂如何影响组织力学和生长素模式。探索罗曼实验室(P5)所研究的茎顶端分生组织中细胞几何形状的变化将提供一个独立的组织几何形状来测试细胞几何形状对生长素构图的影响。理论模拟和实验观察的空前密切的相互作用将为生长素模式动力学和我们对植物组织力学和生化信号在植物发育过程中如何相互交织的理解提供新的基准。

The most influential messenger during plant development is the tiny growth regulator auxin. The phytohormone controls basic processes like cell division and cell growth, and accumulates in patterns underlying the shoot architecture and the leaf vasculature. Thereby auxin controls the dynamic morphology of plants. The patterns of auxin and its carriers PIN and AUX/LAX are dynamic and reorganize throughout plant development. The long history of modelling auxin patterns has recently experienced a reset as the up to then mystical PIN polarity was uncovered to be likely coordinated by mechanical stresses arising within the developing tissue. This finding now suggests the following underexplored feedback cycle between auxin/PIN and tissue mechanics. High auxin concentration in a cell softens adjacent cell walls thereby generating mechanical stresses within the tissue. Mechanical stresses in return feed back on auxin flows as PIN binding is upregulated along stressed cell walls. As tissue mechanics plays a fundamental role in auxin patterning so does cell geometry and biomechanical variations across a tissue. How much cell geometry and biomechanical variation impact auxin patterning is an open question.To address this important question, we here propose to investigate the role of cell geometry and biomechanical variation on auxin patterning by predicting auxin patterning dynamics on segmented tissues from live imaging, and by comparing model predictions to experimental observations. In particular, we will use the natural variability in the auxin dynamics leading up to founder cell selection, marked by two adjacent cells with high auxin concentration, to identify the role of cell geometry in auxin patterning dynamics. Further, we will employ the pivotal and well-known mechanical changes of the overlaying endodermis during lateral root formation as a case study for the role of biomechanical variations across a tissue on auxin patterning. Both case studies will be performed in close feed back with experimental data from the Maizel lab (P6) and will further allow us to explore how cell divisions impact tissue mechanics and auxin patterning. Exploring the variation in cell geometry at the shoot apical meristem as investigated by the Lohmann lab (P5) will provide an independent tissue geometry to test for the impact on cell geometry on auxin patterning. The unprecedented close interaction of theoretical modelling and experimental observations will provide a new benchmark for auxin patterning dynamics and our understanding of how plant tissue mechanics and biochemical signalling are intertwined during plant development.