RUI: Genetic and Epigenetic Mechanisms Generating r1 Gene Complexity in Maize

玉米R基因（red-1）编码一个螺旋-环-螺旋转录因子，决定花青素表达的时间和组织特异性。花青素是一种非必需的植物色素，可以作为基因表达的标记物。R位点表现出基因组印迹和参数化等表观遗传现象。印迹在糊粉蛋白的差异表达中是明显的，这取决于亲本基因的遗传。参数化是表观遗传沉默的一种形式，其中特定等位基因（如R-st）的存在影响敏感等位基因（如R-r）的表达水平。印迹和参数化都与R单倍型的结构特性有关。这些结构特性包括1)单倍型复杂性或基因数量，2)基因结构，例如，是否存在反向重复，3)转座元件插入，以及4)胞嘧啶甲基化。分子遗传学方法将应用于R基因的复杂性和表达问题。具体目标是：1。鉴定玉米小种的R单倍型。将利用这些数据构建系统发育树。花青素分布的组织特异性将被调查，等位基因将从顺诱变性、顺变性和印迹性方面进行表征。利用基因重组将选择的单倍型分离成单个转录单位基因，比较每个基因的花青素分布。定义每个独特的非印迹等位基因的5'侧翼区域，并确定甲基胞嘧啶在DNA中的分布。这项研究的结果将使我们更深入地了解表现表观遗传现象的基因的结构和进化方面，例如玉米R家族。

The maize R gene (red-1) encodes a helix-loop-helix transcription factor that determines the timing and tissue-specificity of anthocyanin expression. Anthocyanin is a non-essential plant pigment that can be used as a marker for gene expression. The R locus exhibits epigenetic phenomena such as genomic imprinting and paramutation. Imprinting is apparent in the differential expression of aleurone depending upon parental inheritance of the gene. Paramutation is a form of epigenetic silencing in which the presence of a specific allele such as R-st affect the level of expression of a sensitive allele such as R-r. Both imprinting and paramutation are linked to structural properties of R haplotypes. These structural properties include 1) haplotype complexity or gene number, 2) gene structure, for example, the presence or absence of inverted repeats, 3) transposable element insertion, and 4) cytosine methylation. A molecular genetic approach will be applied to the problem of R gene complexity and expression. The specific aims are:1. To characterize R haplotypes from races of maize. A phylogenetic tree will be constructed with these data. Tissue specificity of anthocyanin distribution will be surveyed and alleles will be characterized in terms of paramutagenicity, paramutability and imprinting.2. To use genetic recombination to separate selected haplotypes into single transcriptional unit genes to compare the anthocyanin distribution for each gene.3. To define the 5' flanking regions of each of the unique non-imprinting alleles and to determine the distribution of methyl-cytosine in the DNA.The results from this study will give more insight into the structural and evolutionary aspects of genes exhibiting epigenetic phenomena, such as the maize R family.