A High-Resolution Map of Recombination in Maize

PI: Wojtek P. Pawlowski（康奈尔大学），CoPIs: Changbin Chen（明尼苏达大学），Shahryar Kianian（北达科他州立大学），Jarek Pillardy（康奈尔大学）和Ernest Retzel（国家基因组资源中心）该项目的目标是生成第一个全面的、高密度的玉米重组图谱。重组是高等真核生物遗传变异的主要来源；它促进适应，从基因组和种群中清除有害突变，并且是基因组结构的主要决定因素。此外，重组是一种无与伦比的植物育种手段。然而，尽管它很重要，但对影响植物和其他高等真核生物中重组事件分布的因素知之甚少。为了了解重组在玉米基因组中发生的位置，该项目将(1)使用一种新的染色质免疫沉淀测序方法绘制减数分裂双链断裂（DSBs）的分布，DSBs启动减数分裂重组；(2)对玉米9号染色体进行高分辨率交叉重组（CO）和非交叉重组（NCO）；(3)检测9号染色体外几个选定位置的CO率；(4) DSB和CO分布的相关图谱将与局部基因组特征相关，包括表达基因、染色质修饰模式、重复DNA元件和特定DNA序列基序的存在。阐明DSB和CO的分布模式，并确定影响它们的因素，将对理解基因组如何通过重组形成具有巨大的意义，并对植物育种具有实际意义。减数分裂重组产生变异，育种者对其进行选择。这项研究将为育种者提供在引入未改良遗传背景性状时的连锁阻力信息，以及需要多少植株才能找到具有理想基因组合的分离，以及如何在更小的群体和更快的育种周期中开发更有效的育种方法。大约五分之一的玉米基因位于重组率高度降低的区域。在这些地区开发增加重组的方法将允许在玉米育种计划中利用更多的等位基因组合，从而提高育种效率。这一认识将适用于具有类似重组模式的其他作物（如小麦）。加强学生和年轻科学家培训的一系列活动是该项目的固有组成部分，包括针对少数民族服务和小型文理学院和大学的暑期实习计划。该项目的结果将在项目网站（www.rec_hotspots.org）上提供，并存入公共存储库，包括GenBank、GEO、MaizeGDB和NCGR数据库。

PI: Wojtek P. Pawlowski (Cornell University)CoPIs: Changbin Chen (University of Minnesota), Shahryar Kianian (North Dakota State University), Jarek Pillardy (Cornell University) and Ernest Retzel (National Center for Genome Resources) The goal of this project is to generate the first comprehensive, high-density map of recombination in maize. Recombination is the main source of genetic variation in higher eukaryotes; it facilitates adaptation, purges deleterious mutations from genomes and populations, and is a major determinant of genome architecture. In addition, recombination is utilized as an unparalleled instrument of plant breeding. However, despite its importance, little is known about factors that affect the distribution of recombination events in plants and other higher eukaryotes. To understand where recombination takes place in the maize genome, the project will (1) map the distribution of meiotic double-strand breaks (DSBs) that initiate meiotic recombination using a novel chromatin immunoprecipitation-sequencing approach; (2) map at very high-resolution crossover (CO) and some non-crossover (NCO) recombination products for maize chromosome 9; (3) examine CO rates at several selected locations outside chromosome 9; and (4) relate maps of DSB and CO distribution will be related to local genome features, including the presence of expressed genes, chromatin modification patterns, repetitive DNA elements, and specific DNA sequence motifs. Elucidating the DSB and CO distribution patterns, and identifying factors that affect them, will have tremendous implications for the understanding how the genome is shaped by recombination as well as have practical importance for plant breeding.Meiotic recombination generates the variation on which breeders apply selection. This research will provide breeders with information on linkage drag when introducing traits from unimproved genetic backgrounds, on how many plants are required to find segregants with desirable gene combinations, and how to develop more efficient breeding methods with smaller populations and faster breeding cycles. About one-fifth of maize genes are located in regions of highly reduced recombination rates. Developing ways to increase recombination in these regions will allow utilizing higher numbers of allele combinations in maize breeding programs, leading to more efficient breeding. This understanding will be transferable to other crop plants with similar patterns of recombination (e.g. wheat). A number of activities to enhance training of students and young scientists are an inherent part of this project, including summer internship programs targeting minority-serving and small liberal art colleges and universities. Results of this project will be available on the project website (www.rec_hotspots.org) and deposited into public repositories, including GenBank, GEO, MaizeGDB, and the NCGR database.