The B chromosome of maize: Drive and Genomic Conflict

不同品种的玉米有一条不是必需的额外染色体，称为B染色体。根据对其DNA序列的分析，这种染色体具有的特性使其能够在一代又一代中持续存在数百万年，尽管植物并不需要它。虽然这些特性有利于B染色体的成功，但它们往往会对正常的玉米染色体产生负面影响，如染色体断裂和转座元件的激活，这些转座元件有可能在基因组中跳跃并导致突变。将进行遗传和分子分析，以了解这些B染色体特性的性质，以及B染色体的存在如何影响玉米基因组。B染色体似乎参与了玉米染色体的重组，因此了解这些特性将有助于深入了解玉米基因组的性质和变异。这项研究将涉及所有教育水平的参与者，并将涉及遗传学、基因组学和计算生物学方面的培训。玉米额外B染色体是一种新的、自私的遗传系统，它涉及整个染色体，通常影响基因组过程。B染色体通过增加异染色质重组、利用新的减数分裂过程来稳定自身在减数分裂过程中的稳定性、通过延缓形成两个精子的一个有丝分裂中着丝粒的复制以及通过介导含B精子的卵子受精来操纵细胞过程，以确保雄性减数分裂中适当的分离。实验将研究着丝粒不分离的机制，不分离所需的反式作用因子的同一性和功能，单价稳定过程的性质，基因组重组调控的性质，以及基因组冲突的方面，如转座元件的去沉默，识别在某些背景下B染色体导致基因组破碎的基因，以及优先受精中的变异基因。该项目的完成将提供数据，支持理解一个巨大的自私遗传实体的一套增选功能的新范式。这个跨学科的团队将试图理解这个自私的实体，以获得对以前在任何关于遗传驱动和基因组冲突的系统中未曾探索的概念的新见解。将在所有教育级别进行跨生物学科的培训计划和计算分析。这一奖项反映了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。

Varieties of corn have an extra chromosome that is not essential called the B chromosome. This chromosome has properties that, based on analysis of its DNA sequence, have allowed it to persist from one generation to the next for millions of years, despite the fact that it is not needed for the plant. While these properties are beneficial to the success of the B chromosome, they often have negative consequences for the normal corn chromosomes such as chromosome fracture and the activation of transposable elements that have the potential to jump around the genome and cause mutations. A genetic and molecular analysis will be conducted to learn the nature of these B chromosome properties and how the corn genome has been impacted by the presence of the B chromosome. The B chromosome appears to have been involved in restructuring the corn chromosomes, so an understanding of these properties will help provide insight into the nature of, and variation in the maize genome. The research will involve participants at all educational levels and will involve training in genetics, genomics, and computational biology. The supernumerary B chromosome of maize is a novel, selfish genetic system involving a whole chromosome that impacts genomic processes in general. The B chromosome has manipulated cellular processes to ensure proper segregation in male meiosis by increasing recombination in heterochromatin, by using a novel meiotic process to stabilize itself in meiosis, by delaying replication of the centromere at the one mitosis that makes the two sperm, and by mediating fertilization of the egg by B containing sperm. Experiments will examine the mechanism of centromere nondisjunction, the identity and function of the trans-acting factors needed for nondisjunction, the nature of the univalent stabilization process, the nature of the modulation of recombination across the genome, and aspects of genomic conflict such as de-silencing of transposable elements, identifying the gene responsible for genomic shattering by B chromosomes in some backgrounds, and the gene responsible for variation in preferential fertilization. The completion of this project will provide data that support a new paradigm in the understanding of a suite of co-opted functions by a mega selfish genetic entity. The interdisciplinary team will seek to understand this selfish entity to gain new insight into concepts previously unexplored in any system about genetic drive and genomic conflict. A training program across biological disciplines with computational analyses will be conducted at all educational levels.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.