FERONIA receptor kinase as a cell surface-located regulator for RAC/ROP GTPase-mediated auxin signaling

植物激素生长素既控制细胞的生长和分裂，也在决定整体形态方面起着至关重要的作用。生长素信号感知的分子水平细节已经研究了几十年。位于细胞核中的生长素受体复合体与生长素调节的许多过程有关。然而，目前还不清楚这种复合体是否可以解释生长素调节的所有现象，特别是那些发生在细胞膜上的现象。因此，对位于细胞表面的生长素信号机制的探索仍在继续。该项目将扩展以前的工作，表明生长素激活沿细胞膜内表面起作用的主要信号媒介，称为RAC/ROP GTP酶。这些重要的蛋白质可能是激活表面定位反应的媒介。目前的项目将测试跨膜蛋白Feronia是否可能是连接细胞外生长素信号与该系统的缺失环节。具体地说，该项目将确定费洛尼亚的胞外结构域是否直接与一种名为Lorelei样葡萄糖磷脂酰肌醇锚定蛋白1的低分子量细胞外基质蛋白直接相互作用。生物化学方法，如蛋白质免疫共沉淀、下拉试验和细胞生物学方法，将用于测试植物细胞中的这些相互作用，并确定生长素如何影响它们。生长素的直接结合研究将用于测试生长素和费洛尼亚或费洛尼亚复合体之间的受体-配体相互作用。这些关键的实验测试了费洛尼亚作为细胞表面生长素信号装置的潜力，将为一名研究生和一名博士后提供培训。

The plant hormone auxin controls both cell growth and cell division and also has a crucial role in determining overall morphology. The molecular-level details of auxin signal perception have been studied for decades. An auxin receptor complex located in the nucleus has been associated with many auxin-regulated processes. It is not clear, however, that this complex can explain the full range of auxin-regulated phenomena, especially those occurring along the cell membrane. Thus, the search for a cell surface-located auxin signaling mechanism continues. This project will extend previous work showing that auxin activates major signal mediators that function along the inner surface of the cell membrane called RAC/ROP GTPases. These important proteins may act as mediators activating surface-located responses. The current project will test whether the transmembrane protein FERONIA could be the missing link connecting extracellular auxin signals to this system. Specifically, this project will determine whether the extracellular domain of FERONIA directly interacts, alone or in a complex, with a low molecular weight extracellular matrix protein called LORELEI-like glucosylphosphatidylinositol-anchored protein1. Biochemical methods such as protein co-immunoprecipitation, pull-down assays and cell biological methods will be used to test for these interactions in plant cells and determine how auxin affects them. Direct auxin-binding studies will be used to test for receptor-ligand interactions between auxin and FERONIA or FERONIA complexes. These crucial experiments testing the potential of FERONIA as a cell surface auxin signaling apparatus will provide training for one graduate student and one postdoctoral fellow.