Deciphering RLP44-linked LRR-receptor dynamics and signalling specificity at the plasma membrane

为了将外部信号与内在发育程序相结合，植物依赖于一系列扩大的细胞表面受体。这些受体中最大和特征最好的一组是由富含亮氨酸的重复受体样激酶(LRR-RLK)组成的，它感知各种各样的发育和病原体防御相关的线索。LRR-RLK形成了一个广泛的交互网络，这提出了一个中心问题，即如何实现不同的信号响应。质膜的空间组织、受体蛋白的修饰和受调控的运输以及细胞壁的联合都被认为参与了信号的控制。然而，目前尚不清楚这些过程如何在空间和时间上交叉调节质膜受体的动力学和信号输出。最近，我们发现细胞壁结合蛋白RLP44能够与两个不同的LRR-RLK受体复合体相互作用，并调节它们各自的信号活性。因此，RLP44链接的信号通路的复杂相互作用代表了一个理想的系统，以揭示LRR-RLK相互作用网络中特异性是如何实现的。在这个项目中，我们的目标是破译RLP44相关通路的空间和时间协调。为此，我们将利用超分辨显微镜定量RLP44及其配体结合相互作用伙伴在质膜中的动力学，并揭示翻译后修饰和膜转运在控制RLP44相关信号转导中的作用。特别是，我们感兴趣的是细胞壁结合在控制RLP44内化以及确定它参与的相互作用方面的相关性。我们期待从这个项目中获得对LRR-RLK网络中众多信令路径的集成和协调的新见解。

To integrate external cues with intrinsic developmental programs, plants rely on an expanded contingent of cell surface receptors. The largest and best characterized group of these receptors is formed by the leucine-rich-repeat receptor-like kinases (LRR-RLK), which perceive a wide variety of developmental and pathogen defence-related cues. LRR-RLKs form an extensive interaction network, which raises the central question of how distinct signalling responses can be achieved. Spatial organisation of the plasma membrane, modification and regulated trafficking of receptor proteins, as well as cell wall association have all been proposed to be involved in controlling signalling. However, it is unclear how these processes intersect to spatially and temporally modulate plasma membrane receptor dynamics and signalling outputs. Recently, we have revealed that the cell wall-binding protein RLP44 is able to interact with two different LRR-RLK receptor complexes and modulate their respective signalling activities. Thus, the complex interplay of RLP44-linked signalling pathways represents an ideal system to unravel how specificity is achieved within the LRR-RLK interaction network. In this project, we aim to decipher the spatial and temporal coordination of RLP44-associated pathways. To this end, we will quantify dynamics of RLP44 and its ligand-binding interaction partners in the plasma membrane using super-resolution microscopy and unravel the role of posttranslational modification and membrane trafficking in controlling RLP44-associated signalling. In particular, we are interested in the relevance of cell wall binding in controlling internalization of RLP44 as well as in determining the interactions it engages in. We expect from this project novel insight into the integration and coordination of the multitude of signalling pathways within the LRR-RLK network.