Chromatin modifications associated with priming and activation of defense-related genes in Arabidopsis thaliana

在最初接触坏死性病原体后，植物可以在感染和未感染的组织中获得对进一步病原体攻击的抵抗力。这种增强的抗病能力被称为“系统获得性抗性”(SAR)。SAR与某些防御相关(DR)基因启动子的敏化(“启动”)有关。因此，与没有SAR的植物相比，有SAR的植物中相应的转录本积累得更快，并达到更高的水平。本项目旨在阐明有关原发病原体攻击的信息是如何在DR基因启动子水平上实现的。最近的研究表明，染色质结构是由组蛋白的共价修饰等决定的，它控制着基因的转录状态，并能够构成对先前事件的细胞记忆。我们联合起来，将植物病理学和染色质能力结合起来，研究在代表性DR基因的启动和启动子激活过程中的染色质修饰。拟南芥的PAL-1和PAL-2基因将被分析组蛋白乙酰化和甲基化以及核小体密度的变化。我们将比较基因的基本活性状态、启动状态和激活状态。此外，我们将在时程实验中比较与PR-1基因失活和激活状态相关的染色质修饰。记录的染色质修饰模式将在受DR转录积累或组蛋白修饰影响的突变体和过表达品系中进行研究。这些结果将为建立植物的SAR和DR基因的组蛋白密码提供新的见解。

After initial contact with a necrotizing pathogen, plants can acquire resistance to further pathogen attack in both the infected and the non-infected tissue. This type of enhanced disease resistance is called “systemic acquired resistance” (SAR). SAR is associated with a sensitization (“priming”) of the promoters of certain defense-related (DR) genes. Consequently, the corresponding transcripts accumulate faster and to higher levels in plants with SAR as compared to plants without SAR. This project aims to elucidate how the information about primary pathogen attack is realized at the level of DR gene promoters. Recent studies suggested that the chromatin structure which is determined, amongst others, by covalent modification of histones, is controlling the transcriptional state of a gene and is capable of constituting a cellular memory of previous events. We teamed up to bring together phytopathology and chromatin competence to study chromatin modifications during the establishment of priming and promoter activation of representative DR genes. The PAL-1 and PAL-2 genes of Arabidopsis thaliana will be analyzed for changes in histone acetylation and methylation as well as nucleosome density. We will compare the basal activity state, the primed state, and the activated state of the genes. Furthermore, we will compare chromatin modifications associated with the inactivated and activated states of the PR-1 gene in a time-course experiment. The recorded pattern of chromatin modifications will be investigated in mutants and overexpresser lines affected in either DR transcript accumulation or histone modification. The results will provide novel insights into both the establishment of SAR and the histone code of DR genes in plants.