A pathogen-activated transcription program directed by TFIIB-related pBrp1 in plant immunity

植物病原菌可导致农作物严重减产，从而威胁全球粮食安全。了解植物免疫的分子机制最终将有助于开发更好的疾病控制策略。植物免疫的一个组成部分是在病原菌侵染时激活大量与防御相关的基因。这个项目的重点是一个潜在的植物防御基因表达的主要调节因子，在植物免疫中起着关键作用。该项目的主要目标是：1)确定受调节器直接调控的基因谱；2)建立调节器激活植物防御相关基因的机制；3)确定调节器在植物免疫反应激活过程中的调节。这个项目的结果将加深我们对差异基因表达过程的理解，这不仅是植物免疫系统的基础，也是生物体中所有复杂过程的基础。该项目将把研究与培训、学习、多样性和外联活动结合起来。参与该项目的博士后研究员和学生将接受广泛的分子方法的跨学科培训。该项目将融入学生的课堂学习，包括那些来自代表不足群体和高中生的学生，以提高普通公众的科学技术意识。植物免疫中的转录重编程是通过RNA聚合酶II(RNAP II)的募集或释放，通过特定转录因子(TF)的协同作用实现的。RNAP II全酶包含一组通用的转录因子(GTF)，被认为是所有基因转录所必需的。转录因子IIB(TFIIB)是RNAP II的GTF。有趣的是，拟南芥有14个基因编码TFIIB相关蛋白，其中包括6个植物特异的TFIIB相关蛋白(PBrps)。本项目以拟南芥pBrp1为研究对象。Pbrp1突变体在抗病和防御基因的表达上都受到了影响。在未受感染的植物中，pBrp1蛋白保留在叶绿体被膜上，只有当蛋白酶体途径被抑制时，才能检测到核pBrp1。病原菌侵染可诱导pBrp1积聚。这些结果表明，pBrp1是一种特殊的RNAP II全酶的受调控的GTF，它指导着防御基因的转录程序。为了验证这一假设，该项目将使用全基因组转录组图谱和芯片序列来确定pBrp1的直接目标基因。将用免疫共沉淀法确定pBrp1与RNAP II的直接结合，以确认pBrp1是RNAP II的GTF，并确定复合体中与pBrp1的作用和调节有关的其他成分。将对pBrp1的蛋白质水平和核转位进行操作，以确定pBrp1的严格调控对平衡植物防御和适应性的重要性。这些研究将有助于阐明植物免疫的转录调控，以及及时、准确和有效激活植物防御的复杂机制。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Plant pathogens can lead to severe crop yield loss, thereby threatening global food security. Understanding the molecular mechanisms of plant immunity will ultimately help develop better disease control strategies. An integral part of plant immunity is the activation of a large number of defense-related genes upon pathogen infection. This project is focused on a potential master regulator of plant defense gene expression with a critical role in plant immunity. The main goals of the project are to i) identify the spectrum of genes that are directly regulated by the regulator, ii) establish the mechanisms by which the regulator activates plant defense-related genes and iii) determine the regulation of the regulator during the activation of plant immune responses. Results from this project will enhance our understanding of the process of differential gene expression fundamental not only to plant immune systems but also to all complex processes in living organisms. This project will integrate research with training, learning, diversity and outreach activities. Postdoctoral fellows and students working on the project will receive interdisciplinary training in a wide range of molecular approaches. The project will be integrated into classroom learning for students, including those from underrepresented groups and high school students, to increase the general public's awareness of science and technology. Transcription reprogramming in plant immunity is achieved through concerted action of specific transcription factors (TFs) through recruitment or release of RNA polymerase II (RNAP II). The RNAP II holoenzyme contains a group of general TFs (GTFs), which are believed to be required for transcription of all genes. Transcription factor IIB (TFIIB) is a GTF for RNAP II. Interestingly, Arabidopsis have 14 genes encoding TFIIB-related proteins including six plant-specific TFIIB-related proteins (pBrps). This project is focused on Arabidopsis pBrp1. The pbrp1 mutants are compromised in both disease resistance and defense gene expression. In uninfected plants, the pBrp1 protein is retained on the plastid envelop and nuclear pBrp1 is detected only when proteasome pathways are inhibited. Pathogen infection induces pBrp1 accumulation. These results suggest that pBrp1 is a regulated GTF of a special RNAP II holoenzyme that directs a defense gene transcription program. To test this hypothesis, the project will identify the direct target genes of pBrp1 using genome-wide transcriptome profiling and ChIP-seq. The direct association of pBrp1 with RNAP II will be determined using co-immunoprecipitation to confirm pBrp1 is a GTF for RNAP II and to identify other components in the complexes with roles in the action and regulation of pBrp1. The protein levels and nuclear translocation of pBrp1 will be manipulated to determine the importance of the tight regulation of pBrp1 for balancing plant defense with fitness. These studies will help elucidate transcriptional regulation of plant immunity, as well as the intricate mechanisms for timely, accurate and effective activation of plant defense.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.