Analysis of a dominant epigenetic modifier of pericarp color1 (p1) gene of maize

为了了解基因表达的等位基因特异性调控，将玉米果皮色素1 （p1）基因及其红色色素沉着表型作为遗传标记。先前的研究表明，p1位点的等位基因变异是其基因结构、组织和表观遗传调控机制的功能。携带P1-wr（白色果皮和红色穗轴颖片）等位基因的玉米植株产生无色果皮和红色穗轴颖片的穗，这种表型在几代之间是稳定的。然而，在Ufo1 （orange1的不稳定因子）存在的情况下，P1-wr等位基因在包括果皮、穗轴颖花、叶鞘和外壳在内的几种组织中赋予不同程度的增强色素沉着表型。Ufo1是p1表达的主要修饰因子，与p1没有关联。表达研究表明，ufo1诱导的p1调节色素沉着的增加与p1 RNA稳态水平的增加和p1 -wr DNA甲基化的降低有关。为了确定不明飞行物基因的性质及其作用机制，本项目将进行进一步的分子和遗传学表征。第一组实验将精细绘制Ufo1在10S染色体上的位置，这些结果将确定Ufo1基因的候选基因。第二个目标将比较Ufo1如何影响p1的单拷贝和多拷贝等位基因的DNA甲基化。第三个目标将研究ufo1在两个玉米基因座维持参数化中的作用。这项研究将促进目前对重叠表观遗传途径如何独特地调节等位基因特异性模式的理解。这个项目的意义在于它阐明了一类基因表达修饰因子，这些修饰因子可以通过DNA甲基化或特定靶位点染色质的短暂变化来调节或破坏良好编程的表达谱。真核生物的基因调控机制可以限制基因对特定组织或细胞类型的表达。由于等位基因的忠实传递，大多数这样的表达模式得以稳定地维持。然而，有一些机制允许形式和功能的多样化。其中一种机制是表观遗传调控，通过改变DNA甲基化或将DNA包装成染色质。在这个项目中，研究者将使用玉米色素沉着调节基因p1作为模型系统，通过它来了解以等位基因形式施加的组织特异性的分子基础。了解这种以自然和稳定的等位基因形式存在的独特类型的等位基因变异的基础，对致力于开发改良作物的生物学家和植物育种家具有极大的兴趣。本项目将为植物表观遗传学领域的研究生和本科生提供培训。此外，每年夏天，PI都会接待两名来自宾夕法尼亚州州长农业科学学院的实习生，进行玉米遗传学和分子生物学的独立研究项目。PI还参与了几个针对代表性不足的本科生的指导项目，并与乔治亚州少数族裔服务机构Fort Valley州立大学的Sarwan Dhir博士合作，开展了一个由美国国家科学基金会资助的REU项目，为少数族裔和妇女提供植物生物学、遗传学和生物技术领域的教育和培训。

To understand allele-specific regulation of gene expression, the maize pericarp color1 (p1) gene and its red pigmentation phenotype have been used as a genetic marker. Previous studies demonstrated that allelic variation at the p1 locus is a function of its gene structure, organization, and epigenetic regulatory mechanisms. Maize plants carrying the P1-wr (white pericarp & red cob glumes) allele produce ears with colorless kernel pericarp and red cob glumes and this phenotype is stable over generations. However, in the presence of Ufo1 (Unstable factor for orange1), the P1-wr allele confers variably enhanced pigmentation phenotypes in several tissues that include pericarp, cob glume, leaf sheath and husk. Ufo1 is a dominant modifier of p1 expression and it is unlinked from p1. Expression studies demonstrated that Ufo1-induced gain of p1 regulated pigmentation is associated with increased steady state levels of p1 RNA and decreased DNA methylation of P1-wr. To identify the nature of ufo1 gene and the mechanism of its action, further molecular and genetic characterization will be performed during this project. The first set of experiments will fine map the position of Ufo1 on chromosome 10S and these results will identify candidates for the ufo1 gene. The second objective will compare how the DNA methylation of single copy and multicopy alleles of p1 are affected by Ufo1. The third objective will examine the role of ufo1 in the maintenance of paramutation in two maize loci. This research will advance the current understanding of how overlapping epigenetic pathways uniquely regulate allele-specific patterns. The significance of this project is its elucidation of a class of modifiers of gene expression that can regulate or disrupt a well-programmed expression profile via transient changes in the DNA methylation or chromatin of specific target loci. Eukaryotic gene regulatory mechanisms can restrict the expression of a gene to a specific tissue or a cell type. Most such patterns of expression are stably maintained due to the faithful transmission of alleles. Nevertheless, there are mechanisms that allow diversification of form and function. One such mechanism is epigenetic regulation operating through alterations in DNA methylation or in the packaging of DNA into chromatin. In this project the investigator will use the maize pigmentation regulatory gene p1 as a model system through which to understand the molecular basis of tissue specificity imposed in the form of alleles. to Understanding the basis of this unique type of allelic variability that exists in the form of natural and stable alleles is of great interest to biologists and plant breeders working to develop improved crops. This project will provide training for graduate and undergraduate students in the field of plant epigenetics. Furthermore, each summer the PI hosts two interns from the Pennsylvania Governor's School for Agricultural Sciences for independent study projects in maize genetics and molecular biology. The PI also participates in several mentoring programs for underrepresented undergraduates and collaborates with Dr. Sarwan Dhir of Fort Valley State University, a minority-serving institution in Georgia, in an NSF-funded REU program providing education and training to minorities and women in the field of plant biology, genetics and biotechnology.