RESEARCH-PGR: Controlling recombination in maize

减数分裂重组是一个过程，其中两个亲本染色体，一个来自父亲，另一个来自母亲，交换部分产生下一代。这个过程在后代中产生了新的遗传变异，这有助于适应新的环境，并从基因组中清除有害的突变。减数分裂重组是进化的主要机制之一，也是植物和动物育种的无与伦比的工具。然而，尽管它们很重要，重组事件在整个基因组中并不是均匀分布的。相反，它们主要发生在称为重组热点的不同位点。与其他真核生物相比，人们对植物中控制重组的机制知之甚少，特别是对作物中的重组知之甚少，作物往往具有大而复杂的基因组。该项目的目标是确定基因组中的特定位点如何成为玉米中的重组热点，模式物种以及主要作物，重组热点如何演变，以及如何修改它们以改进植物育种方法。大部分玉米基因位于重组非常有限的区域。开发增加这些地区重组的方法将允许更有效的育种。为了进一步传播有关减数分裂重组的知识，参与该项目的实验室将联合运营一个科学本科少数民族实习和培训（SUMMIT）计划，该计划每年将为少数民族本科生提供三次为期10周的实习。本项目的目标是阐明玉米减数分裂重组景观，并获得修改它的能力。减数分裂重组开始于染色体DNA中双链断裂（DSB）的程序性形成。DSB的修复导致染色体臂的相互交换，称为交叉（CO）。在包括玉米在内的大多数物种中，减数分裂产生大量的DSB，但很少有DSB成为CO。此外，尽管DSB普遍存在于整个玉米基因组中，但大多数CO靠近染色体末端。这个项目将研究染色质以及DNA序列如何影响CO景观，以及如何重组机制的知识可以用来改变CO景观。为了了解染色质和染色体特征在塑造CO分布中的作用，将研究染色质状态的影响以及同源染色体相互作用对CO形成进展的动力学。还将研究基因组序列和CO模式之间的关系，以了解遗传多样性如何影响CO景观。为了测试从该项目中获得的重组基因组学知识，并将其应用于实际目的，将检查人工CO热点的有效性。这项研究将提供一个更完整的图片重组是如何控制在植物中，并促进有效的工具，利用它的植物育种的发展。该奖项由整合有机系统部的植物基因组研究计划和分子与细胞生物科学部的遗传机制集群共同资助。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Meiotic recombination is a process in which two parental chromosomes, one from the father and the other one from the mother, exchange parts to give rise to the next generation. This process creates new genetic variation in the progeny, which facilitates adaptation to new environments and purges detrimental mutations from genomes. Meiotic recombination is one of the main mechanisms of evolution and is also an unparalleled instrument of plant and animal breeding. However, despite their importance, recombination events are not evenly distributed throughout the genome. Instead, they predominantly take place at distinct sites called recombination hotspots. Compared to other groups of eukaryotes, little is understood about the mechanisms controlling recombination in plants, and particularly little is known about recombination in crops, which tend to have large and complex genomes. The goal of this project is to determine how specific sites in the genome become recombination hotspots in maize, a model species as well as a major crop, how recombination hotspots evolve, and how they can be modified to improve plant breeding methods. A large fraction of maize genes are located in regions that show very limited recombination. Developing ways to increase recombination in these regions will allow more efficient breeding. To further spread the knowledge about meiotic recombination, the laboratories participating in this project will jointly operate a Science Undergraduate Minority Mentoring Internship and Training (SUMMIT) program, which each year will sponsor three 10-week internships for minority undergraduate students. The goal of this project is to elucidate the meiotic recombination landscape in maize and gain the ability to modify it. Meiotic recombination starts with a programmed formation of double-strand breaks (DSBs) in chromosomal DNA. Repair of the DSBs leads to reciprocal exchanges of chromosome arms called crossovers (COs). In most species, including maize, large numbers of meiotic DSBs are generated but very few of them become COs. Furthermore, although DSBs are ubiquitously present throughout the entire maize genome, most COs are near chromosome ends. This project will examine how chromatin as well as DNA sequence affect CO landscape and how the knowledge of recombination mechanisms can be used to alter CO landscape. To understand the role of chromatin and chromosome characteristics in shaping CO distribution, the impact of chromatin state, and the dynamics of homologous chromosome interactions on the progression of CO formation will be investigated. The relationship between genome sequence and CO patterns will also be studied to understand how genetic diversity affects CO landscapes. To test the knowledge on recombination genomics gained from this project, and to apply it for a practical purpose, effectiveness of artificial CO hotspots will be examined. This research will provide a more complete picture of how recombination is controlled in plants and facilitate development of efficient tools to harness it for plant breeding. This award was co-funded by the Plant Genome Research Program in the Division of Integrative Organismal Systems and the Genetic Mechanisms Cluster in the Division of Molecular and Cellular Biosciences.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.