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。该项目旨在扩展我们对自交不亲和系统进化生物学的知识。 自交不亲和性是植物避免近亲繁殖的主要机制。 自交不亲和性的丧失被假设为自花授粉进化的第一步，这是植物中最常见的进化转变之一。 拟议的研究重点是Leavenoprotia属，那里有多个交配系统的转换。 它集中在S-位点，它由两个紧密相连的基因组成，SRK（在识别自花花粉中起作用）和SCR（编码SRK产物识别的配体）。该基因座最近已在几种芥菜中克隆，我们的实验室已将这些结果扩展到Leavenoclavia。本文报道了一种Leavenacroia（L.）Alabamica）最近被测序。 我们建议建立在这一进展，以解决以下问题：（1）S位点突变发生在低频率的自交不亲和群体？(2)当自交亲和性进化时，通常是由于SCR突变还是SRK突变？(3)在S基因座上产生自交亲和群体的突变选择的性质和强度是什么？(4)为什么自交类群在进化时间上似乎是短命的？我们将对来自人群的样本进行高通量重新测序，对S位点突变进行详细的分子分析，对S位点进行表达分析，并进行田间实验。对自交的遗传基础的研究迄今仅限于少数类群。 目前还不知道在单一基因座的突变在多大程度上导致自交和选择什么类型的突变。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，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。所解决的问题是重要的，以了解自交类群，这代表了显着比例的显花植物和不成比例的作物物种的进化和长期前景。

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.