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

【摘要】研究者已经对玉米果皮色素基因p1 （pericarp color1）等位基因的表达模式和基因结构进行了研究。P1是一种myb型转录因子，控制红色类黄酮色素的生物合成。先前的研究结果表明，p1位点的等位基因表达是基因结构和基因组织的功能，并进一步受到表观遗传机制的调控。研究者现在已经描述了一种称为Ufo1 （orange1的不稳定因子）的显性修饰因子。在Ufo1缺失的情况下，P1-wr（白果皮和红穗轴）等位基因植株的果皮无色，穗轴红，且该表型高度稳定。在Ufo1存在的情况下，P1-wr赋予不同程度的增强果仁、果皮、穗轴和植物色素沉着。初步表达研究表明，色素沉着的增加与p1转录本稳态水平的增加有关，p1转录本稳态水平的增加与启动子DNA甲基化和p1 -wr编码序列的减少有关。进一步的实验将通过p1等位基因的瞬时DNA甲基化改变来研究Ufo1诱导的编程良好的表达谱的去调控。具体而言，1)使用亚硫酸盐测序方法，本项目将确定Ufo1存在时p1序列中DNA甲基化修饰的特定类型和位置；2)通过微阵列分析Ufo1与Ufo1基因型RNA鉴定的基因将进一步测试其表达和功能；3)克隆Ufo1基因。该研究项目将开始开发植物种群，以在10号染色体短臂上已知的原始位置内精细绘制Ufo1因子。从长远来看，这项研究将导致鉴定可能调节转基因和天然等位基因稳定性的分子标记和机制。研究生和本科生将在这个项目中进行大部分的研究。该项目将提供表观遗传学和功能基因组学方面的培训机会。

Chopra AbstractThe investigator has previously characterized the expression pattern and gene structure of alleles of the maize p1 (pericarp color1) gene. P1 is a myb type of transcription factor and controls the biosynthesis of red flavonoid pigments called phlobaphenes. Previous findings suggest that allelic expression at the p1 locus is a function of the gene structure and gene organization, which is further regulated by epigenetic mechanisms. The investigator has now characterized a dominant modifier called Ufo1 (Unstable factor for orange1). In the absence of Ufo1, plants of P1-wr (white pericarp & red cob glumes) allele produce ears with colorless kernel pericarp and red cobs and this phenotype is highly stable. In the presence of Ufo1, the P1-wr confers variably enhanced kernel pericarp, cob and plant pigmentation. Preliminary expression studies demonstrate that the gain of pigmentation is associated with increased steady state levels of p1 transcript that is correlated with decrease in DNA methylation of promoter and coding sequence of the P1-wr. Further experiments will investigate Ufo1 induced de-regulation of a well-programmed expression profile via transient DNA methylation changes of p1 alleles. Specifically, 1) using bisulfite sequencing methods, this project will identify specific type(s) and position(s) of DNA methylation modifications in the p1 sequence in the presence of Ufo1, 2) genes identified from the microarray analysis of Ufo1 versus ufo1 genotype RNA will be further tested for their expression and functionality and 3) to clone the Ufo1 gene, the research project will begin to develop plant populations to fine map the Ufo1 factor within the known crude position on the short arm of chromosome 10. In the longer run, this study will lead to the identification of molecular marks and mechanisms that may regulate stability of transgenes and natural alleles. Graduate students and undergraduates students will perform the majority of the research on this project. This project will provide training opportunities in epigenetics, as well as in functional genomics.