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，决定花色素苷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，可用作基因表达的标记。R基因座表现出表观遗传现象，如基因组印记和副突变。印记在糊粉层的差异表达中是明显的，这取决于基因的亲本遗传。平行突变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。印记和副突变都与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目，2）基因结构，例如反向重复序列的存在或不存在，3）转座因子插入，和4）胞嘧啶甲基化。一个分子遗传学的方法将被应用到R基因的复杂性和表达的问题。具体目标是：1.鉴定玉米小种的R单倍型。将用这些数据构建系统发育树。研究花色苷分布的组织特异性，并对等位基因的准突变性、准突变性和印迹性进行表征.利用遗传重组技术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.确定每个非印记等位基因的5'侧翼区，并确定甲基胞嘧啶在DNA中的分布，这一研究结果将有助于深入了解表现表观遗传现象的基因（如玉米R家族）的结构和进化方面。

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.