Plant development relies on the precise coordination of cell growth, which is influenced by the mechanical constraints imposed by rigid cell walls. The hormone auxin plays a crucial role in regulating this growth by altering the mechanical properties of cell walls. During the postembryonic formation of lateral roots, pericycle cells deep within the main root are triggered by auxin to resume growth and divide to form a new root. This growth involves a complex interplay between auxin, growth, and the resolution of mechanical conflicts with the overlying endodermis. However, the exact mechanisms by which this coordination is achieved are still unknown. Here, we propose a model that integrates tissue mechanics and auxin transport, revealing a connection between the auxin-induced relaxation of mechanical stress in the pericycle and auxin signaling in the endodermis. We show that the endodermis initially limits the growth of pericycle cells, resulting in a modest initial expansion. However, the associated stress relaxation is sufficient to redirect auxin to the overlying endodermis, which then actively accommodates the growth, allowing for the subsequent development of the lateral root. Our model uncovers that increased pericycle turgor and decreased endodermal resistance license expansion of the pericycle and how the topology of the endodermis influences the formation of the new root. These findings highlight the interconnected relationship between mechanics and auxin flow during lateral root initiation, emphasizing the vital role of the endodermis in shaping root development through mechanotransduction and auxin signaling.

中文翻译：

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生长素介导的中柱鞘和内胚层重塑中的应力松弛驱动侧根萌生


植物发育依赖于细胞生长的精确协调，而细胞生长受到刚性细胞壁施加的机械约束的影响。生长素激素通过改变细胞壁的机械特性在调节这种生长方面发挥着至关重要的作用。在侧根的胚后形成过程中，主根深处的中柱鞘细胞被生长素触发恢复生长并分裂形成新根。这种生长涉及生长素、生长以及与上覆内皮层的机械冲突的解决之间复杂的相互作用。然而，实现这种协调的确切机制仍然未知。在这里，我们提出了一个整合组织力学和生长素运输的模型，揭示了生长素诱导的中柱鞘机械应力松弛与内皮层生长素信号传导之间的联系。我们发现内皮层最初限制了中柱鞘细胞的生长，导致初始适度扩张。然而，相关的应力松弛足以将生长素重定向到覆盖的内皮层，然后内皮层积极适应生长，从而允许侧根的后续发育。我们的模型揭示了中柱鞘膨压的增加和内胚层抵抗力的降低允许中柱鞘的扩张以及内皮层的拓扑结构如何影响新根的形成。这些发现强调了侧根起始过程中力学和生长素流动之间的相互关联关系，强调内皮层通过机械转导和生长素信号传导在塑造根发育中的重要作用。