The B chromosome of maize: Drive and Genomic Conflict

各种各样的玉米都有一条额外的染色体，它被称为B染色体，这条染色体不是必需的。根据对其DNA序列的分析，这条染色体具有一些特性，使它能够从一代持续到下一代数百万年，尽管事实上植物并不需要它。虽然这些特性有利于B染色体的成功，但它们通常对正常的玉米染色体有负面影响，如染色体断裂和转座因子的激活，这些转座因子有可能在基因组周围跳跃并导致突变。将进行遗传和分子分析，以了解这些B染色体特性的本质，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，因此对这些特性的理解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。玉米的多余B染色体是一种新的、自私的遗传系统，涉及整个染色体，影响基因组过程。B染色体通过增加异染色质的重组，利用一种新的减数分裂过程在减数分裂中稳定自身，在一次有丝分裂中延迟产生两个精子的着丝粒的复制，以及通过介导含有B的精子对卵子的受精，来操纵细胞过程以确保男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身份和功能，单价稳定过程的性质，基因组重组调节的性质，以及基因组冲突的方面，如转座元件的去沉默，确定在某些背景下由B染色体负责基因组破碎的基因。这个基因负责优先受精的变异。这个项目的完成将提供数据，支持一个新的范式来理解一个超级自私的遗传实体的一套增选功能。这个跨学科的团队将试图理解这个自私的实体，以获得新的见解，了解以前在任何关于遗传驱动和基因组冲突的系统中未被探索的概念。将在所有教育水平进行跨生物学学科的计算分析培训计划。该奖项反映了美国国家科学基金会的法定使命，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。

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.