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。除了增加进化的基础知识，这些结果对作物育种有重要意义，特别是当作物在密切相关的非作物物种存在的情况下出现时。这项研究将集中在猴花，Mimulus guttatus，一种草本野花，主要分布在太平洋西北部。它以多年生和一年生形式出现，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的差异的基础，并测试关于基因排列如何控制进化的假设。研究人员将使用遗传工具解剖一年生和多年生生态型之间的染色体倒位。这种倒置与生活史表达密切相关，并已被证明会显著影响自然界中的表现。以前的QTL定位发现，与生活史相关的遗传变异的很大一部分映射到一个大的臂间染色体倒位，分离两个生态型。然而，由于重组之间的抑制染色体的倒置和共线部分时，发现在一个杂合子，映射内的倒位是不可能的，在这个物种对。使用经典的QTL作图以及NIL系，研究人员将：（1）在多种条件下创建一个全基因组的生活史分歧图，（2）测试倒位如何有助于田间生活史分歧，以及（3）研究选择如何作用于倒位内的等位基因。研究人员将测试倒位是否已经捕获了生活史性状的常设遗传变异，因此由于其重组抑制特性，可能会通过间接选择而被锁定。这项工作将有助于阐明倒位有助于当地适应的机制，并最终，倒位如何保持遗传多样性，尽管适应不良的基因流。

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.