Mechanisms and mechanics of lateral root initiation

侧根（LR）是由拟南芥主根深处的几个创始细胞胚后形成的。LR的形成是一个生长素诱导的，强大的，自组织的过程，需要相邻的创始人细胞对径向扩展之前，他们不对称分裂。未能准确执行这些步骤会导致异常LR的形成。在第一个资助阶段获得的结果表明，创始人细胞成对的安排，生长素的分布，创始人细胞的径向扩张和侧根发生之间的联系。然而，负责共享壁两侧LR创始细胞同步和镜像径向扩张的机制仍然难以捉摸。在这里，我们建议破译这些机制，特别侧重于力学。我们将使用实时成像和有针对性地操纵细胞特性，如生长素含量，细胞壁力学和质外质pH值以及机械建模，以了解两个创始人之间的界面如何为LR启动所必需和充分。我们将揭开同步径向膨胀是如何触发的。以及生长素诱导的胞外pH调节在这一过程中所起的作用。该项目将揭示元素细胞特性的协调修饰如何通过开发作为新器官形态发生的强大触发因素。

Lateral roots (LR) are post-embryonically formed from few founder cells located deep into the main root of Arabidopsis. LR formation is an auxin-induced, robust, self-organizing process that requires that abutting pairs of founder cells to radially expand before they divide asymmetrically. Failure to execute these steps accurately results in formation of aberrant LRs. Results obtained during the first funding phase suggest a link between the arrangement of founder cells in pairs, distribution of auxin, the radial expansion of the founder cells and lateral root initiation. However, the mechanisms responsible for the synchronous and mirror-imaged radial expansion of both LR founder cells on each side of the shared wall remain elusive. Here, we propose to decipher these mechanisms with a particular focus on mechanics. We will use live imaging and targeted manipulation of cells properties such as auxin content, cell wall mechanics and apoplasmic pH together with mechanical modelling to understand how the interface between two founders necessary and sufficient for LR initiation. We will unravel how is the synchronous radial expansion triggered. As well as the role played by modification of the extracellular pH induced by auxin in this process. This project will reveal how the coordinated modifications of elemental cell properties is leveraged by development as a robust trigger for morphogenesis of a new organ.