Cyclic nucleotide-gated ion channel (CNGC)-mediated signal transduction and hormonal crosstalk in plant natural immunity

背景：*由于全球人口增长，增加粮食产量是世界上一个紧迫的问题。然而，尽管大量使用可能损害环境的农用化学品，每年仍有大量农产品因植物病害而损失。因此，对植物免疫的了解和寻找增强计划自然抵抗力的方法是未来粮食生产安全和健康环境的关键。*到目前为止，我们已经证明了环核苷酸门控离子通道CNGC11和12在植物免疫中发挥着重要作用，并分析了它们的结构-功能关系。我们还使用了CNGC突变体来检测信号串扰。在动物中，CNGC影响视觉和嗅觉信号转导，并受钙传感器蛋白钙调蛋白(CaM)的调节。然而，在植物中，CNGC及其下游信号转导通路的调节机制在很大程度上仍不清楚。**研究目标和提纲：*我研究的长期目标是在分子水平上了解环境应激与病原体感染相结合的信号转导途径和网络。为此，在接下来的5年里，我们将：1)鉴定和表征CNGC介导的信号转导的组成成分；2)研究CNGC的调节；3)研究激素串扰和环境对植物免疫的影响。*对于AIM I，我们鉴定了CNGC2缺失突变体dnd1(防御不死亡1)的抑制子rdd1，它显示了一种自身免疫表型。因此，RDD1可能作用于CNGC2介导的抗病信号的下游，或作用于影响CNGC2信号的信号级联。这项拟议的工作将在分子水平上研究RDD1在CNGC介导的抗性信号中的参与。此外，我们还确定了另外五个抑制因子，我们将对其进行表征和鉴定。*AIM II涉及CAM对CNGC的监管。动物CNGC研究表明，CaM结合负调控CNGCs；然而，CaM对植物CNGCs的调控尚不清楚。在这项建议中，我们将确定植物CNGC中的CaM结合域，并表征它们在病原体侵染时的结合动力学。*目的III解决水杨酸(SA)、脱落酸(ABA)和生长素之间的串扰。SA是植物免疫的关键信号分子，SA、ABA和生长素之间的复杂串扰强烈影响植物的抗病能力。这表明，一个协调的信号网络允许植物分配资源来对抗病原体，对非生物胁迫做出反应，并保持生长。此外，我们目前的数据表明，环境因素影响CNGC信号转导。为了确定这种串扰中的关键节点，我们对ABA和SA诱导的蛋白质进行了酵母双杂交分析，发现了几种可能介导串扰的候选相互作用。在这项建议中，我们将分析这些候选基因的分子机制，并进行SA和生长素信号成分之间的另一种相互作用组分析。**预测意义：*这项建议的结果将有助于我们理解CNGC介导的植物免疫反应。此外，激素串扰在植物免疫中已成为一个重要的话题，因为它与环境条件有关。目前，尽管大量使用昂贵的农用化学品，但植物病害每年都会造成农产品的重大损失。此外，不稳定的气候条件可能会增加疾病爆发的频率。因此，拟议的计划将对农业研究产生重大影响，以提高可持续人类社会的植物抗病能力。

BACKGROUND:*Due to global population growth, increasing food production is an urgent issue in the world. However, significant amounts of agricultural products are lost annually due to plant disease in spite of the extensive usage of agrochemicals that may harm the environment. Thus, the understanding of plant immunity and finding ways to enhance natural resistance of plans is the key for security of food production and a healthy environment in the future. *To date, we have shown that the cyclic nucleotide-gated ion channels CNGC11 and 12 play significant roles in plant immunity and we have analyzed their structure-function relationships. We also used a CNGC mutant to examine signal crosstalk. In animals, CNGCs affect visual and olfactory signal transduction and are regulated by the calcium sensor protein calmodulin (CaM). However, in plants, the regulators of CNGCs and their downstream signal transduction cascades remain largely unknown. **RESEARCH OBJECTIVE AND OUTLINE:*The long-term goal of my research is to understand the signal transduction pathways and networks integrating environmental stresses with pathogen infection at the molecular level. To this aim, over the next 5 years we will: I) Identify and characterize components of CNGC-mediated signal transduction, II) Investigate the regulation of CNGCs, and III) Investigate hormonal crosstalk and environmental effects on plant immunity.*For aim I, we identified rdd1, a suppressor of the CNGC2 null mutant dnd1 (defense no death1), which displays an autoimmune phenotype. Thus, RDD1 likely acts downstream of CNGC2-mediated disease resistance signaling or on a signaling cascade that affects CNGC2 signaling. The proposed work will investigate the involvement of RDD1 in CNGC-mediated resistance signaling at the molecular level. Furthermore, we identified five additional suppressors, which we will characterize and identify. *Aim II addresses regulation of CNGCs by CaM. Animal CNGC research showed that CaM binding negatively regulates CNGCs; however, the regulation of plant CNGCs by CaM remains unclear. In this proposal, we will determine the CaM binding domains in plant CNGCs and characterize their binding kinetics upon pathogen infection.*Aim III addresses the crosstalk between salicylic acid (SA), abscisic acid (ABA) and auxin. SA is a key signaling molecule in plant immunity and the complex crosstalk among SA, ABA and auxin strongly influences disease resistance. This suggests a coordinated signaling network allowing plants to allocate resources to fight pathogens, respond to abiotic stresses and maintain growth. In addition, our current data indicate that environmental factors affect CNGC signaling. To identify the key nodes in this crosstalk, we conducted a yeast two-hybrid analysis of ABA- and SA-inducible proteins and discovered several candidate interactions that may mediate crosstalk. In this proposal, we will analyze molecular mechanisms of these candidates and conduct another interactome analysis between SA and auxin signaling components.**PREDICTED SIGNIFICANCE:*The outcome of this proposal will significantly contribute to our understanding of CNGC-mediated plant immune responses. Furthermore, hormonal crosstalk in plant immunity has emerged as an important topic, since it is related to environmental conditions. Currently, plant diseases cause significant annual losses of agricultural products, despite the extensive use of costly agro-chemicals. In addition, unstable climate conditions may increase the frequency of disease outbreaks. Thus, the proposed program will significantly impact agricultural research to improve plant disease resistance for a sustainable human society.