Two Types of Meiotic Crossovers in Higher Plants

高等植物减数分裂交叉的两种类型

• 批准号: 1019708
• 负责人: Lorinda Anderson
• 金额: $ 49.75万
• 依托单位: Colorado State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1019708&HistoricalAwards=false
• 关键词: Two; Types; Meiotic; Crossovers; Higher

Intellectual merit: During sexual reproduction, each pair of homologous chromosomes typically requires a minimum of one (obligate) crossover to assure proper segregation of chromosomes and production of genetically balanced haploid gametes. At least two pathways lead to crossovers in budding yeast, mammals, and plants: the MLH1 pathway with interference (in which the presence of one crossover reduces the likelihood of another crossover nearby) and the MUS81 pathway that is thought to show little or no interference. How crossover frequency and distribution are controlled and how different crossover pathways interact are two fundamental questions in genetics that have both theoretical and practical implications in genome evolution, speciation, and plant and animal breeding. Evaluating the two crossover pathways at a genome-wide level is difficult because the two types of crossovers cannot be distinguished using linkage mapping. In contrast, a cytogenetic immunolabeling approach is ideal because it allows individual crossovers of each type to be unequivocally identified and localized. This project will directly evaluate the contribution of each pathway to crossing over and interference in higher plants using light (LM) and electron microscopic (EM) immuno¬localization of MLH1 and MUS81 proteins on pachytene chromosomes of tomato (Solanum lycopersicum). MLH1 is a component of most late recombination nodules (LNs). LNs mark crossover sites and have been extensively studied in tomato. MUS81 is thought to be a component of MLH1-negative LNs, and EM immunolocalization will be used to test that hypothesis. Subsequent work will use simultaneous LM immunolocalisation of MLH1 and MUS81 to map these foci on pachytene chromosome spreads from wild-type tomato plants and from MLH1 and MUS81 gene-silenced lines. These data on the roles of the two types of crossovers under different genetic situations will be exploited within a comprehensive mathematical model of crossing over. This work will be the first to perform such investigations in any species and will provide novel insights into the contributions and interactions of both interference and non-interference types of crossovers at a genome-wide level in flowering plants. Broader Impacts: This work will define the contribution and interaction of two different crossover pathways in both normal and mutant flowering plants. This information will be useful in designing breeding approaches to target regions of special interest for genetic recombination in order to improve agricultural lines. Useful tools generated in the study (such as antibodies and transgenic plants) will be shared with colleagues. The development of human resources is an important part of the work, and one graduate student and one post-doctoral fellow will be closely involved in the research. Each will receive individual attention and regular mentoring by the principal investigator, and both will receive training in a laboratory that specializes in plant gene-silencing approaches at the University of Nebraska. In addition undergraduate students will be involved in many aspects of the research. After an initial training period, each undergraduate will be encouraged to work on an independent project that supports the overall goals of the research and to present their research results at a yearly forum for undergraduates at Colorado State University (CSU) called Celebrate Undergraduate Research and Creativity. Underrepresented and minority students will be specifically recruited by working in partnership with the McNair Program at CSU.

智力优势：在有性繁殖过程中，每对同源染色体通常需要至少一个(专有的)交叉，以确保适当的染色体分离和产生遗传平衡的单倍体配子。在萌芽中的酵母、哺乳动物和植物中，至少有两条途径导致交叉：带有干扰的MLH1途径(其中一个交叉的存在降低了附近发生另一个交叉的可能性)和被认为几乎没有干扰的MUS81途径。如何控制交叉频率和分布以及不同的交叉途径如何相互作用是遗传学中的两个基本问题，在基因组进化、物种形成和动植物育种中都具有理论和实践意义。在全基因组水平上评估这两种交叉途径是困难的，因为使用连锁图谱无法区分这两种类型的交叉。相反，细胞遗传学免疫标记方法是理想的，因为它允许明确地识别和定位每种类型的个体交叉。本项目将利用番茄粗线期染色体上MLH1和MUS81蛋白的光(LM)和电子显微镜(EM)免疫定位，直接评估每条途径对高等植物互换和干扰的贡献。MLH1是大多数晚期重组结节(LNS)的组成部分。LNS标记了交叉位点，并在番茄中得到了广泛的研究。MUS81被认为是MLH1阴性LNS的一个组成部分，EM免疫定位将用于验证这一假设。后续工作将使用MLH1和MUS81的同时LM免疫定位来定位来自野生型番茄植株以及MLH1和MUS81基因沉默品系的粗线期染色体扩散的这些焦点。这些关于两种类型的杂交在不同遗传情况下的作用的数据将在一个全面的杂交数学模型中加以利用。这项工作将是首次在任何物种中进行此类调查，并将为在开花植物基因组水平上干扰和非干扰类型的交换的贡献和相互作用提供新的见解。更广泛的影响：这项工作将定义在正常和突变的开花植物中两种不同的交叉途径的贡献和相互作用。这些信息将有助于设计针对遗传重组特别感兴趣的目标区域的育种方法，以改进农业品系。研究中产生的有用工具(如抗体和转基因植物)将与同事共享。人力资源开发是这项工作的重要组成部分，一名研究生和一名博士后将密切参与研究。每个人都将接受首席研究人员的个别关注和定期指导，两人都将在内布拉斯加大学专门研究植物基因沉默方法的实验室接受培训。此外，本科生还将参与多方面的研究。在最初的训练期后，每个本科生将被鼓励参与一个独立的项目，以支持研究的总体目标，并在科罗拉多州立大学(CSU)为本科生举办的名为庆祝本科生研究和创造力的年度论坛上展示他们的研究成果。代表不足和少数族裔的学生将通过与密歇根州立大学麦克奈尔项目的合作来具体招收。