A Radiation Hybrid and Cloning System for the Genetic and Physical Mapping of the Corn Genome

用于玉米基因组遗传和物理作图的辐射杂交和克隆系统

• 批准号: 9872650
• 负责人: Ronald Phillips
• 金额: $ 183.07万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-10-01 至 2002-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9872650&HistoricalAwards=false
• 关键词: Radiation; Hybrid; Cloning; System; Genetic

An efficient means to map genes of corn would facilitate understanding the genetic makeup of corn, our major cereal crop. The genome size and complexity of corn is similar to that of humans with a DNA content of about 2.5 billion base pairs. The placement of human genes in their respective chromosomes is greatly facilitated by the use of special Chinese hamster cell lines containing portions of the human genome. An analogous system is proposed for corn gene mapping with the production of oat lines containing portions of the corn genome. Crosses of oats with corn pollen followed by the rescue of early developing embryos on a nutrient medium leads to the recovery of plants with only one corn chromosome together with all the oat chromosomes. Such plants are termed oat-maize chromosome addition lines. The complexity of the corn genome is reduced by 10-fold in these plants. Irradiation of these plants possessing a single corn chromosome can produce an array of progenies with less than the whole corn chromosome present. Such progeny are termed radiation hybrids. A series of radiation hybrids allows the placement of corn genes to short but highly defined regions of the genome. The goal of this project is to complete the series of the 10 different oat-com chromosome addition lines (7 are currently available) and, for each chromosome, produce a series of approximately 100 radiation hybrid lines. Proof of concept has been completed with a radiation hybrid series for chromosome 9. A series of only 12 radiation hybrids allowed chromosome 9 to be delineated into 22 distinct subregions. The average size of these regions, given certain assumptions, is estimated to be 8.7 Mb. About 100 evenly distributed genetic markers and 100 radiation hybrids would be necessary to define corn chromosome 9 regions at the 2 Mb level; 600 markers would be needed to adequately utilize a 400 kb level of resolution. Advantages of this approach - in addition to high resolution mapping -is that any gene can be mapped without the availability of polymorphic forms, the gene's physical chromosome location becomes known, and the system is especially suitable for high-throughput formats. Arrays of DNA samples ultimately will be available to researchers for mapping any gene or DNA fragment to a small region of a given chromosome. Other uses of the radiation hybrids include the cloning of small segments of corn chromosomes separated from the remaining portions of the genome, the isolation of additional markers in a small genomic region perhaps as tags for important traits, and the identification of oat lines with useful traits such as disease resistance or heat stress tolerance incorporated from corn into oat.

绘制玉米基因图谱的有效方法将有助于了解玉米的基因构成，玉米是我们的主要谷类作物。玉米的基因组大小和复杂性与人类相似，DNA含量约为25亿个碱基对。通过使用包含部分人类基因组的特殊中国仓鼠细胞系，极大地促进了人类基因在各自染色体中的放置。提出了一种类似的系统，用于玉米基因定位，产生包含部分玉米基因组的燕麦品系。将燕麦与玉米花粉杂交，然后在营养培养基上挽救早期发育的胚胎，可以恢复只有一个玉米染色体和所有燕麦染色体的植株。这种植物被称为燕麦-玉米染色体附加系。在这些植物中，玉米基因组的复杂性降低了10倍。对这些只有一条玉米染色体的植物进行辐射，可以产生一系列的后代，而这些后代的染色体数量比目前存在的整个玉米染色体还少。这种后代被称为辐射杂交种。一系列辐射杂交种允许将玉米基因定位到基因组的较短但高度明确的区域。该项目的目标是完成10个不同燕麦-玉米染色体附加系的系列(目前已有7个)，并为每个染色体产生一系列大约100个辐射杂交系。概念验证已经完成，9号染色体的辐射杂交系列已经完成。只有12个辐射杂交系列允许将9号染色体划分为22个不同的亚区。在某些假设下，这些区域的平均大小估计为8.7Mb。大约100个均匀分布的遗传标记和100个辐射杂交组合将需要在2Mb水平上定义玉米9号染色体区域；需要600个标记才能充分利用400kb的分辨率水平。这种方法的优势--除了高分辨率作图--是任何基因都可以在没有多态形式的情况下进行作图，基因的物理染色体位置是已知的，并且该系统特别适合高通量形式。DNA样本阵列最终将提供给研究人员，用于将任何基因或DNA片段映射到给定染色体的一个小区域。辐射杂交的其他用途包括克隆从基因组剩余部分分离出来的玉米染色体的小片段，在一个小基因组区域分离额外的标记，可能作为重要性状的标签，以及鉴定具有有用特征的燕麦品系，如将玉米的抗病或耐热胁迫纳入燕麦。