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 unpublished).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.

食草性昆虫在植物群落的调节中起着重要的作用，作为粮食作物的害虫，对农业生态系统的影响也很大。近年来，我们目睹了多次爆发的“超级害虫”，这是一种多面手的食草动物，它们迅速在新的地区定居，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，现在发现昆虫获得对新寄主的耐受性的机制，以预测和控制新出现的害虫暴发是及时和关键的。这个博士项目将采用实验进化、建模和生理操纵实验，采取跨学科的方法来了解饮食专业化和泛化演变的机制。实验将使用模式系统Callosobruchus maculatus进行，这是一种世界性的储存豆类害虫，其系统地理记录中有很好的寄主转移记录，并且有良好的基因组资源可用(Arnqvist等人)。未出版)。我们课题组最近的工作表明，DNA甲基化是该物种寄主偏好的重要调节因子，但我们尚不清楚在整个进化过程中和适应新寄主的过程中，这一过程是如何运作的。我们目前在实验室里维持着这个物种的几个实验品系，它们已经进化成表达不同程度的饮食通用性。利用这些现有的线路，学生将：1)试验性地施加新的环境，允许多面手和专家谱系的斑点毛虫在多个世代中殖民新资源。我们将使用“进化和重测序”类的实验方案来监测多个种群中世代的等位基因频率，从而产生时间序列数据。Kosiol团队为实验性进化研究的轨迹设计了高斯过程模型，学生将使用该模型来评估与这些进化转变相关的等位基因分歧模式。2)使用公认的可以使DNA高甲基化或低甲基化的药物，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甲基化或缺失如何影响引入新资源后选择的等位基因反应的性质。3)学生将评估与宿主植物转移相关的DNMT1(DNA甲基转移酶1，负责将DNA甲基化标签转移到新合成的DNA链上的酶)基因表达的进化变化，首次量化进化过渡期间DNA甲基化活性的时间变化。学生还将有机会进行有针对性的测序，以评估候选基因座(例如，上面的1和2)启动子区DNA甲基化模式的进化变化。这项研究的结果将为发现新的害虫控制机制提供潜在的数据，特别是防止害虫入侵新的作物品种。这项研究还将为进化过程提供新的、普遍的见解。学生将在实验进化、基因组技术(湿实验室和生物信息学)和统计建模方面获得有价值的和可移植的技能。