DISSERTATION RESEARCH: Understanding the Role of Chromosomal Inversions in Life History Divergence and Local Adaptation in Mimulus

该项目的目标是更好地了解染色体上的基因排列在维持遗传多样性方面的作用，这是进化过程的基础。除了增加进化的基本知识外，这些结果对作物育种具有重要意义，特别是当作物生长在密切相关的非作物物种存在时。这项研究将集中在猴花，一种主要分布在太平洋西北地区的草本野花。它以多年生和一年生形式存在，它们是独特的，并在当地适应各自的栖息地。通过使用遗传工具，研究人员将发现这些形式之间差异的基础，并测试有关基因安排如何控制进化的假设。研究人员将使用遗传工具来解剖一种染色体倒置，这种染色体倒置在一年生和多年生的麻瓜生态型之间变化。这种倒置与生命史表达密切相关，并已被证明对自然界的表现有显著影响。先前的qtl定位发现，与生活史相关的大部分遗传变异映射到分离两种生态型的大的中心周围染色体反转。然而，由于在杂合子中发现染色体的倒位部分和共线部分之间的重组受到抑制，因此在该物种对中不可能在倒位部分内进行定位。利用经典的qtl定位和NIL线，研究人员将：(1)创建多种条件下生活史分化的全基因组图谱，(2)在该领域测试反转如何促进生活史分化，以及(3)研究选择如何作用于反转中的等位基因。研究人员将测试这种反转是否捕获了生活史特征的遗传变异，从而由于其抑制重组的特性，有可能通过间接选择而固定下来。这项工作将有助于阐明倒序促进局部适应的机制，并最终阐明倒序如何在不适应基因流的情况下保持遗传多样性。

The goal of this project is to gain a better understanding of the role of gene arrangements on chromosomes in maintaining genetic diversity, which is fundamental to the process of evolution. Beyond adding to basic knowledge of evolution, these results have important implications for crop breeding, especially when crops occur in the presence of closely related non-crop species. The study will focus on monkeyflower, Mimulus guttatus, an herbaceous wildflower that is distributed predominantly in the Pacific Northwest. It occurs both as perennial and annual forms, which are distinct and locally adapted to their respective habitats. Through the use of genetic tools, the researchers will discover the bases of the differences between those forms and test hypotheses about how gene arrangements control evolution.The researchers will use genetic tools to dissect a chromosomal inversion which varies between annual and perennial ecotypes of Mimulus guttatus. This inversion is strongly associated with life history expression, and has been shown to influence performance in nature significantly. Previous QTLs mapping has found that a large proportion of the genetic variance associated with life history maps to a large pericentric chromosomal inversion that separates the two ecotypes. However, since recombination is suppressed between inverted and collinear portions of a chromosome when found in a heterozygote, mapping within the inversion is impossible in this species pair. Using classical QTLs mapping, as well as NIL lines, the researchers will: (1) create a genome-wide map of life history divergence under multiple conditions, (2) test how the inversion contributes to life history divergence in the field, and (3) examine how selection acts on alleles within the inversion. The researchers will test whether the inversion has captured standing genetic variation for life history traits, and thus has potentially swept to fixation by indirect selection due to its recombination suppression properties. This work will help elucidate the mechanism by which inversions contribute to local adaptation, and ultimately, how inversions can maintain genetic diversity despite maladaptive gene flow.