Analysis of the molecular mechanisms of plant defense against microbial pathogens

感知和防御微生物感染对多细胞生物体的生存至关重要。植物主要利用两种免疫受体识别病原体并激活下游防御反应。跨膜受体被用来识别微生物的保守特征，如细菌鞭毛蛋白，而细胞内受体与核苷酸结合和富含亮氨酸的重复结构域(NLR)被用来检测分泌到植物细胞中促进定植的特定蛋白质。这项拟议的研究旨在了解这两种免疫受体介导的免疫是如何在分子水平上调节的。*植物免疫的激活导致快速转录重新编程。我们以前的研究发现，SARD1是一种主要的转录因子，调节着大量关键免疫调节因子的表达。SARD1的表达受病原菌侵染的强烈诱导，SARD1表达的增加足以激活植物对病原菌的防御。我们要解决的一个大问题是，定位于质膜的免疫受体如何传递防御信号，从而激活细胞核中SARD1的表达。我们将结合使用分子遗传学、基因组学和生物化学的方法来识别和表征参与这一过程的调控成分。另一个与跨膜免疫受体介导的免疫有关的问题是，异源三聚体G蛋白如何调节受体下游关键信号成分的蛋白质水平。自从大约20年前在拟南芥中首次报道NLR受体以来，许多植物NLR蛋白已经被鉴定出来，并在它们如何识别病原体方面取得了巨大的进展。然而，关于NLR受体是如何激活下游防御反应的，人们仍然知之甚少。我们以前的研究发现了几种与NLR受体SUMM2介导的免疫相关的蛋白质。我们将测试它们是否在SUMM2下游发挥作用，传递防御信号，并确定它们是如何调节植物免疫的。这项研究可能有助于深入了解NLR受体是如何传递防御信号来激活植物防御的。*我们的研究对于促进我们对植物免疫如何调控的了解至关重要。参与植物防御反应的新的调控因子和信号机制将被发现。所获得的知识将有助于制定更好的战略，通过环境友好的手段控制植物病害。**

Sensing and defending against microbial infection is essential to the survival of multicellular organisms. Plants mainly use two types of immune receptors to recognize pathogens and activate downstream defense responses. Transmembrane receptors are used to recognize conserved features of microbes such as bacterial flagellin, whereas intracellular receptors with nucleotide binding and leucine-rich repeats domains (NLRs) are used to detect specific proteins from pathogens that are secreted into the plant cell to promote colonization. The proposed research aims to understand how immunity mediated by these two types of immune receptors is regulated at molecular level.*** *** Activation of plant immunity leads to rapid transcriptional reprogramming. Our previous studies identified SAR Deficient 1 (SARD1) as a master transcription factor which regulates the expression of a large number of key immune regulators. The expression of SARD1 is strongly induced by pathogen infection and increase in SARD1 expression is sufficient to activate plant defense against pathogens. One big question we are going to address is how defense signals are transduced from plasma membrane-localized immune receptors to activate the expression of SARD1 in the nucleus. We are going to use a combination of molecular genetic, genomic and biochemical approaches to identify and characterize regulatory components involved in the this process. Another question related to immunity mediated by transmembrane immune receptors which we are going to address is how heterotrimeric G proteins regulate the protein level of a critical signaling component downstream of the receptors. ****** Since the first report of NLR receptors in Arabidopsis about two decades ago, many plant NLR proteins have been identified and tremendous progress has been made on how they recognize pathogens. However, there is still very little known about how NLR receptors activate downstream defense responses. Our previous studies identified several proteins that are involved in immunity mediated by the NLR receptor SUMM2. We are going to test whether they function downstream of SUMM2 to transduce defense signals and determine how they regulate plant immunity. This investigation may lend insights on how defense signals are transduced from NLR receptors to activate plant defense.****** Our research is crucial for advancing our knowledge of how plant immunity is regulated. New regulators and signaling mechanisms involved in plant defense responses will be discovered. The knowledge obtained will contribute to the development of better strategies to control plant diseases through environmentally friendly means. **