Molecular analysis of leucine rich-repeat receptor protein-mediated immune signaling

富含亮氨酸重复序列受体蛋白介导的免疫信号传导的分子分析

• 批准号: 338295721
• 负责人: Professor Dr. Thorsten Nürnberger
• 金额: --
• 依托单位: Abteilung für Pflanzenbiochemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/338295721?language=en
• 关键词: Molecular; analysis; leucine; rich; repeat

Leucine-rich repeat (LRR) ectodomain-containing PRRs mediate recognition of proteinaceous immunogenic patterns. LRR-type PRRs exist in two forms as LRR receptor kinases (LRR-RK), which carry an intracellular protein kinase domain, and LRR receptor proteins (LRR-RP) that lack a functional intracellular domain. It has recently been hypothesized that LRR-RP/SOBIR1 heteromeric complexes (SOBIR1 is an LRR-RK itself), constitutively formed in the absence of ligands, are equivalent to bi-molecular or bipartite LRR-RK-type PRRs. The proposed identity of molecular mechanisms underlying immune activation mediated through either LRR-RK or LRR-RP-type PRRs has yet to be shown. In fact, our recent findings have challenged this hypothesis to an extent that justifies a more in-depth comparative analysis of signaling networks and physiological outputs mediated through activation of either receptor type. Substantial differences were observed between Arabidopsis LRR-RK FLS2 and Arabidopsis LRR-RP RLP23-mediated cellular responses. For example, the cytoplasmic protein kinase BIK1, known as a positive regulator of flg22-induced ROS burst, acts as a negative regulator of nlp20-induced ROS burst and ethylene production; both amplitude and kinetics of flg22- and nlp20-mediated ROS burst differ substantially, and nlp20-treatment of Arabidopsis Col-0 resulted in the production of camalexin, whereas flg22-treatment did not. To characterize and compare LRR-RK and LRR-RP-mediated immune signaling, we propose to conduct a systematic analysis of pattern-specific signal transduction and of immune responses mediated through two LRR-RK-type PRRs (FLS2, EFR) or through two LRR-RPs (RLP23, RLP42). This research will reveal to which extent signaling pathways activated through LRR-RK and LRR-RP-type differ as well as whether there are differences in signaling networks and signal outputs mediated through activation of the same receptor types. We will further test whether chimeric receptors in which kinase domains of FLS2 and SOBIR1 were replaced with one another would turn flg22 perception into an nlp20 output response and vice versa. If so, this would suggest a strictly modular composition of these receptor types. We further propose to assess the mechanistic basis for BIK1-mediated negative regulation of nlp20 signaling. Here, we will analyze whether this novel function requires BIK1 protein kinase activity, whether BIK1 physically associates with SOBIR1 in ligand (in)dependent fashion, whether nlp20-specific phosphorylation of BIK1 is observed, whether BIK1 phosphorylates substrates (such as RbohD) in an nlp20-specific manner or whether putative novel BIK1-interacting proteins (substrates) can be identified that might explain the differential involvement of BIK1 in flg22/FLS2 and nlp20/RLP23-mediated immune signaling.

富含亮氨酸重复序列（LRR）的胞外域PRR介导蛋白质免疫原性模式的识别。LRR型PRR以两种形式存在，即携带细胞内蛋白激酶结构域的LRR受体激酶（LRR-RK）和缺乏功能性细胞内结构域的LRR受体蛋白（LRR-RP）。最近有人假设，LRR-RP/SOBIR 1异聚体复合物（SOBIR 1本身就是一种LRR-RK），在不存在配体的情况下组成型形成，相当于双分子或二分LRR-RK型PRR。通过LRR-RK或LRR-RP-型PRR介导的免疫激活的分子机制的拟议身份尚未显示。事实上，我们最近的研究结果在一定程度上挑战了这一假设，证明了通过激活任一受体类型介导的信号网络和生理输出的更深入的比较分析是合理的。在拟南芥LRR-RK FLS 2和拟南芥LRR-RP RLP 23介导的细胞应答之间观察到实质性差异。例如，细胞质蛋白激酶BIK 1，已知为flg 22诱导的ROS爆发的正调节剂，充当nlp 20诱导的ROS爆发和乙烯产生的负调节剂; flg 22和nlp 20介导的ROS爆发的幅度和动力学两者实质上不同，并且拟南芥Col-0的nlp 20处理导致camalexin的产生，而flg 22处理没有。为了表征和比较LRR-RK和LRR-RP介导的免疫信号传导，我们建议对模式特异性信号转导和通过两种LRR-RK型PRR（FLS 2，EFR）或通过两种LRR-RP（RLP 23，RLP 42）介导的免疫应答进行系统分析。这项研究将揭示通过LRR-RK和LRR-RP-type激活的信号通路在多大程度上不同，以及通过激活相同受体类型介导的信号网络和信号输出是否存在差异。我们将进一步测试其中FLS 2和SOBIR 1的激酶结构域被彼此替换的嵌合受体是否会将flg 22感知转化为nlp 20输出响应，反之亦然。如果是这样，这将表明这些受体类型的严格模块化组成。 我们进一步提出评估BIK 1介导的nlp 20信号负调控的机制基础。在这里，我们将分析这种新的功能是否需要BIK 1蛋白激酶活性，BIK 1是否以配体依赖性方式与SOBIR 1物理缔合，是否观察到BIK 1的nlp 20特异性磷酸化，BIK 1是否磷酸化底物（例如RbohD）以nlp 20特异性方式或是否是推定的新型BIK 1相互作用蛋白可以鉴定出可以解释BIK 1在flg 22/FLS 2和nlp 20/RLP 23介导的免疫信号传导中的差异参与的底物。