RESEARCH-PGR: Controlling recombination in maize

减数分裂重组是指两条双亲染色体，一个来自父亲，另一个来自母亲，交换部分以产生下一代的过程。这一过程在后代中创造了新的遗传变异，从而促进了对新环境的适应，并清除了基因组中有害的突变。减数分裂重组是进化的主要机制之一，也是动植物育种无与伦比的工具。然而，尽管重组事件很重要，但重组事件并不均匀地分布在整个基因组中。相反，它们主要发生在称为重组热点的不同位置。与其他真核生物相比，人们对植物中重组的控制机制知之甚少，尤其是对作物中的重组知之甚少，因为农作物往往具有巨大而复杂的基因组。该项目的目标是确定玉米基因组中的特定位置如何成为重组热点，玉米是模式物种和主要作物，重组热点是如何进化的，以及如何对它们进行修改以改进植物育种方法。很大一部分玉米基因位于重组非常有限的区域。在这些地区开发增加重组的方法将允许更有效的育种。为了进一步传播减数分裂重组的知识，参与该项目的实验室将联合开展理科本科生少数民族辅导实习和培训(SUMPLE)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的减数分裂重组景观，并获得对其进行修饰的能力。减数分裂重组始于染色体DNA双链断裂的程序性形成。DSB的修复导致染色体臂的相互交换，称为交叉(Cos)。在包括玉米在内的大多数物种中，都会产生大量的减数分裂DSB，但很少会成为CoS。此外，虽然DSB普遍存在于整个玉米基因组中，但大多数CoS都在染色体末端附近。本项目将研究染色质和DNA序列如何影响一氧化碳景观，以及如何利用重组机制的知识来改变一氧化碳景观。为了了解染色质和染色体特征在形成CO分布中的作用，我们将研究染色质状态和同源染色体相互作用对CO形成过程的影响。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。为了检验从这个项目中获得的重组基因组学知识，并将其应用于实际目的，将检验人工一氧化碳热点的有效性。这项研究将提供一个更完整的图景，如何在植物中控制重组，并促进开发有效的工具来利用它进行植物育种。该奖项是由综合组织系统部门的植物基因组研究计划和分子和细胞生物科学部门的遗传机制集群共同资助的。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.