Population genomic studies of mating system transitions

我们的实验室研究植物生殖系统的进化和遗传学。这个项目建议扩展我们对自交不亲和系统的进化生物学的知识。自交不亲和是植物避免近亲繁殖的主要机制。自交不亲和性的丧失被认为是自花授粉进化的第一步，自花授粉是植物中最常见的进化转变之一。建议的研究集中在利文沃西亚属，那里已经有了多次交配系统的转变。它集中在S基因座上，它由两个紧密连锁的基因组成，srk(负责识别自交花粉)和scr(编码srk产物识别的配体)。该基因座最近在几种芥菜中被克隆，我们的实验室已经将这些结果推广到Levenworth ia。利文沃斯属(L.alabamica)的一个物种的基因组最近被测序。我们建议在这一进展的基础上解决以下问题：(1)S基因座突变在自交不亲和群体中是否以低频率发生？(2)当自交亲和进化时，通常是由于Scr突变还是SRK突变？(3)导致自交不亲和群体的S基因突变的选择的性质和强度是什么？(4)为什么自交分类群在进化时间内似乎是短暂的？我们将对人群样本进行高通量重测序，对S基因座突变进行详细的分子分析，对S基因座进行表达分析，并进行现场实验。到目前为止，对自交的遗传基础的研究仅限于少数几个分类群。目前尚不清楚单个基因座的突变在多大程度上会导致自交，也不知道选择了什么类型的突变。这项拟议的工作将是第一批评估选择作用于导致自交的突变的强度的研究之一，并采用全基因组水平的方法来研究自交的进化如何影响基因组进化。所讨论的问题对于理解自交分类群的进化和长期前景很重要，自交分类群占开花植物的很大比例，而且作物物种的数量不成比例。

Our lab investigates the evolution and genetics of reproductive systems in plants. This project proposes to extend our knowledge of the evolutionary biology of self-incompatibility systems. Self-incompatibility is the major mechanism by which plants avoid inbreeding. The loss of self-incompatibility is hypothesized to be the first step in the evolution of self-pollination, an evolutionary transition that is among the most common in plants. The proposed research focuses on the genus Leavenworthia, where there have been multiple mating system transitions. It centers on the S-locus, which consists of two tightly linked genes, SRK (which functions in the recognition of self-pollen) and SCR (which codes for a ligand recognized by the SRK product). The locus has recently been cloned in several mustard species, and our lab has extended these results to Leavenworthia. The genome of one species of Leavenworthia (L. alabamica) has recently been sequenced. We propose to build upon this progress to address the following questions: (1) Do S-locus mutations occur at low frequencies in self-incompatible populations? (2) When self-compatibility evolves, is it generally due to mutations in SCR or to mutations SRK? (3) What is the nature and strength of selection on mutations at the S-locus that have given rise to populations with self-compatibility? (4) Why do selfing taxa appear to be short-lived in evolutionary time? We will conduct high throughput re-sequencing of samples from populations, detailed molecular analysis of S-locus mutations, expression analyses of the S-locus, and field experiments. Studies of the genetic basis of selfing have so far been restricted to a few taxa. It is not known to what extent mutations at single loci lead to selfing and what types of mutations are selected. The proposed work will be among the first studies to assess the strength of selection acting on mutations that cause selfing, and to adopt a whole genome level approach to investigating how the evolution of selfing influences genome evolution. The issues addressed are important to understanding the evolution and long-term prospects of selfing taxa, which represent a significant proportion of flowering plants and a disproportionate number of crop species.