拟南芥泛素连接酶BAR1在植物天然免疫中的功能

Plants live in an environment with a diverse array of microorganisms. Innate immunity (composed of PTI & ETI) is important for plants to thwart off a broad spectrum of potential pathogens. The FLS2-mediated signaling is one of the best-characterized PTI pathways. However, there are still gaps in the PTI signaling. For example, what is the component directly downstream to BIK1, a key player in PTI signaling ? Based on our preliminary data, we found that a RING ubiquitin ligase, BAR1 (BIK1 Associated RING Ubiquitin Ligase1) was associated with BIK1. Furthermore, the association between BAR1 and BIK1 was enhanced by flg22 treatment. Additionally, BIK1 is able to phosphorylate BAR1 in vitro. To investigate the exact role of BAR1 in PTI signaling and elucidate the relationship between BAR1 and BIK1 in FLS2-mediated signaling, we are planning to perform the following experiments using multiple approaches: the confirmation of interaction between BAR1 and BIK1 both in vitro and in vivo; immunity phenotype analysis of BAR1-derived T-DNA mutants and over-expression transgenic plants; examining the function of BAR1 phosphorylation by BIK1 in innate immunity; configuring out the role of E3 ubiquitin ligase activity of BAR1 in PTI signaling.

病害是影响农作物产量的重要因素之一。植物对于病原菌的防御主要依赖于天然免疫等系统。植物天然免疫包含PTI和ETI 两个层面。FLS2介导的免疫是研究最为广泛的PTI信号通路之一，但仍有许多"盲点"，如BIK1的下游组分仍然未知。 在前期工作中，我们发现一个拟南芥RING类泛素连接酶，BAR1（BIK1 Associated RING Ubiquitin Ligase1），可以与BIK1的相结合，而且flg22的处理可以促进二者的结合。同时，BIK1能磷酸化BAR1。为了解析BAR1与BIK1在免疫通路中的关系，阐明BAR1在免疫信号转导中的功能，我们将开展以下研究：1）分析BAR1遗传材料的免疫表型，2）解析BIK1磷酸化BAR1的功能，3）鉴定BAR1的泛素连接酶活性在免疫信号转导中的作用等。

植物对于病原菌的防御主要依赖于天然免疫系统。植物天然免疫包含PTI和ETI 两个层面。FLS2介导的免疫是研究最为广泛的PTI信号通路之一。蛋白质泛素化在天然免疫信号转导过程中发挥重要的调控作用。但目前已报道的免疫组分泛素化均为多聚泛素化。对于单泛素化在天然免疫中的调控作用知之甚少。我们发现，一个拟南芥RING类泛素连接酶，BAR1（BIK1 Associated RING Ubiquitin Ligase1），可以与BIK1相结合，并对BIK1发生单泛素化修饰。BAR1及其同源基因BAR2的双突变体对于flg22处理较野生型更加敏感，对丁香假单胞杆菌的抗性较野生型更强，因此BAR1/2在天然免疫中起负调控作用。另外，在本项目开展过程中，为了研究BAR1 对BIK1的泛素化修饰，我们建立了一套研究蛋白质泛素化的新方法。利用合成生物学的手段，将编码植物蛋白泛素化组分的五个基因在同一大肠杆菌细胞中表达，从而实现了植物泛素化途径在细菌中的重建。该系统提供了一种研究植物蛋白质泛素化的新方法。