Evolution and epigenetic regulation of host plant choice in a specialised herbivore, the global crop pest seed beetle Callosobruchus maculatus

一种专门的草食动物——全球作物害虫种子甲虫 Callosbruchus maculatus 宿主植物选择的进化和表观遗传调控

• 批准号: 2282264
• 金额: --
• 依托单位: University of Aberdeen
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2282264
• 关键词: Evolution; epigenetic; regulation; host; plant

Herbivorous insects play important roles in regulating plant communities, and have large effects on agro-ecosystems as pests on food crops. In recent years, we have witnessed repeated outbreaks of 'super-pests', generalist herbivores that have rapidly colonised new regions and are capable of feeding on novel plant types. However, the mechanisms by which insects switch their host plant feeding strategies (between specialism and generalism) are largely unknown. Thus it is now timely and critical to discover the mechanisms by which insects can gain tolerance of novel hosts, in order to predict and contain emerging pest outbreaks. This PhD project will employ experimental evolution, modelling, and physiological manipulative experiments, taking an interdisciplinary approach to understanding the mechanisms by which dietary specialisation and generalisation evolve.Experiments will be run using the model system Callosobruchus maculatus, a worldwide pest on stored legumes with well documented host shifts in its phylogeographic record, and for which good genomic resources are available (Arnqvist et al. unpublished). Recent work in our group suggests that DNA methylation is an important regulator of host preference in this species, but we do not yet know how this operates throughout evolutionary time and in the process of adaptation to novel hosts. We are currently maintaining several experimental lines of this species in the laboratory, which have been evolved to express various degrees of dietary generalism. Using these existing lines, the student will:1) Experimentally impose novel environments which allow generalist and specialist lineages of C. maculatus to colonise novel resources over multiple generations. We will use an 'evolve and resequence' class of experimental protocols to monitor allele frequencies over the generations in multiple populations resulting in time-series data. The Kosiol group has devised Gaussian process models for the trajectories of experimental evolution studies, which the student will use to evaluate patterns of allelic divergence associated with these evolutionary transitions. 2) Using well-established drugs that can hyper- or hypo-methylate DNA, the student will examine the functional role of DNA methylation on adaptation to novel resources. The student will then identify how DNA methylation, or lack of it, affects the nature of the allelic response to selection following introduction of novel resources.3) The student will assess evolved shifts in gene expression of DNMT1 (DNA methyltransferase 1, the enzyme responsible for transferring DNA methylation tags to newly-synthesised strands of DNA) associated with host plant shifts, quantifying for the first time temporal variation in DNA methylation activity during evolutionary transitions. The student will also have the opportunity to conduct targeted sequencing to assess evolutionary changes in the patterns of DNA methylation in promoter regions of candidate loci (e.g., from 1&2, above).Results of this study will provide data with the potential to support the discovery of new pest control mechanisms, especially to prevent pests from invading new crop varieties. This study will also provide new, general insight into the evolutionary process. The student will gain valuable and transferrable skills in experimental evolution, genomic techniques (wet lab and bioinformatics) and statistical modelling.

草食性昆虫在调节植物群落中发挥着重要作用，并且像粮食作物害虫一样对农业生态系统产生巨大影响。近年来，我们目睹了“超级害虫”的反复爆发，这种多面食草动物迅速占领了新的地区，并能够以新的植物类型为食。然而，昆虫改变寄主植物取食策略（在专业性和通用性之间）的机制在很大程度上是未知的。因此，现在及时且关键的是发现昆虫获得新宿主耐受性的机制，以预测和遏制新出现的害虫爆发。该博士项目将采用实验进化、建模和生理操纵实验，采用跨学科方法来理解饮食专业化和泛化进化的机制。实验将使用模型系统 Callosobchus maculatus 进行，这是一种世界性的储存豆类害虫，具有良好的在其系统发育地理学记录中记录了宿主的转变，并且可以获得良好的基因组资源（Arnqvist 等人未发表）。我们小组最近的工作表明，DNA 甲基化是该物种宿主偏好的重要调节因子，但我们还不知道它在整个进化过程中以及在适应新宿主的过程中如何运作。我们目前在实验室中维护着该物种的几个实验品系，这些品系已经进化到能够表达不同程度的饮食普遍性。使用这些现有的品系，学生将：1）通过实验施加新的环境，使 C. maculatus 的通才和专才谱系能够在多代中殖民新资源。我们将使用“进化和重新测序”类实验方案来监测多个群体中几代人的等位基因频率，从而产生时间序列数据。 Kosiol 小组为实验进化研究的轨迹设计了高斯过程模型，学生将用它来评估与这些进化转变相关的等位基因分歧模式。 2) 使用可以使 DNA 过度甲基化或低甲基化的成熟药物，学生将研究 DNA 甲基化在适应新资源方面的功能作用。然后，学生将确定 DNA 甲基化或缺乏 DNA 甲基化如何影响引入新资源后等位基因对选择的反应的性质。3) 学生将评估 DNMT1（DNA 甲基转移酶 1，负责酶）基因表达的进化变化。用于将 DNA 甲基化标签转移到与宿主植物转变相关的新合成的 DNA 链上，首次量化了进化转变过程中 DNA 甲基化活性的时间变化。学生还将有机会进行靶向测序，以评估候选基因座启动子区域 DNA 甲基化模式的进化变化（例如，上面的 1 和 2）。这项研究的结果将提供有可能支持这一发现的数据新的害虫防治机制，特别是防止害虫入侵作物新品种。这项研究还将为进化过程提供新的、普遍的见解。学生将获得实验进化、基因组技术（湿实验室和生物信息学）和统计建模方面宝贵且可转移的技能。