Evolutionary consequences of facultative plant parasitism

寄生是自然界中的一种普遍现象，对宿主、寄生虫及其群落产生巨大影响。有超过3,000种描述的寄生植物，包括槲寄生，重要的草原植物Rhinanthus和农业害虫Striga。一个特别有趣的，但研究很少的群体是兼性半寄生虫，它可以独立于宿主生长和繁殖，但在宿主附着后生长得更旺盛。兼性半寄生是一种非常灵活的生长策略，在专性寄生生物的研究中，这在很大程度上被忽视了，因为专性寄生生物需要宿主来完成其生命周期。本计画从演化遗传学的观点探讨兼性半寄生的个案研究，大戟属约有300种，皆为兼性半寄生。这一建议将取得进展，对使用这个属作为一个研究系统，调查兼性半寄生的进化后果，在两个方面。首先，它将提供资金来测试新兴的基因组方法，开发新的协议，并产生正在进行的研究所需的初步数据。这将包括测试一种新的叶绿体基因组富集方法，应用组织特异性RNA测序方法，以及开发全基因组序列草案。这些资源将是必不可少的未来工作，确定基因座参与兼性半寄生虫的进化，并测试植物寄生虫是否是一个适应性水平基因转移的载体。其次，该提案将在英国植物进化基因组学研究人员，植物寄生虫学世界专家，植物基因组学领导者和Euphrasia生物学国际专家之间开展国际合作。这种国际合作借鉴了美国寄生植物研究的悠久历史，以及欧洲大陆的Euphrasia生物学知识，以综合的方式解决有关半寄生的问题。对植物寄生的进一步了解将极大地有益于许多研究领域，包括进化生物学，植物生物学，寄生虫学和基因组生物学。特别是，了解与寄生相关的基因组变化将是有益的研究人员感兴趣的主要生活史转变的遗传基础，而宿主附着过程中的转录变化的理解将展示一个戏剧性的例子，在一个有机体的生活中的基因表达变化。更一般地说，鉴定不同植物寄生虫寄生生长的共同基因座，将促进遗传工具的开发，以解决作为农业害虫生长的寄生植物。

Parasitism is a widespread phenomenon in the natural world, with dramatic consequences for hosts, parasites, and their communities. There are over 3,000 described parasitic plant species, including mistletoes, the important grassland plant Rhinanthus, and the agricultural pest Striga. A particularly interesting, yet poorly studied group, are the facultative hemiparasites-which can grow and reproduce independent of a host, but grow more vigorously after host attachment. Facultative hemiparasitism represents a remarkably flexible growing strategy, which has largely been overlooked in preference of studies of obligate parasites-organisms which require a host to complete their lifecycle. This project investigates a case study of facultative hemiparasitism, from an evolutionary genetic perspective.The genus Euphrasia contains approximately 300 species, all of which are facultative hemiparasites. This proposal will make progress towards using this genus as a study system for investigating the evolutionary consequences of facultative hemiparasitism, on two fronts. Firstly, it will provide the funds to test emerging genomic approaches, develop new protocols, and produce preliminary data, required for ongoing research in Euphrasia. This will include testing a new chloroplast genome enrichment approach, applying a tissue-specific RNA sequencing method, and the development of a draft whole genome sequence. These resources will be essential for future work identifying loci involved in the evolution of facultative hemiparasites, and testing whether plant parasites are a vector for adaptive horizontal gene transfer. Secondly, this proposal will develop an international collaboration between a UK researcher in plant evolutionary genomics, the world expert in plant parasitism, a leader in plant genomics, and an international expert in the biology of Euphrasia. Such an international collaboration draws on the long history of research of parasitic plants in the USA, as well as the knowledge of Euphrasia biology centred in mainland Europe, to tackle questions about hemiparasitism in an integrated fashion.An increased understanding of plant parasitism will greatly benefit many areas of research, including evolutionary biology, plant biology, parasitology, and genome biology. In particular, understanding genomic changes associated with parasitism will be informative for researchers interested in the genetic basis of major life history transitions, while an understanding of transcriptional changes during host attachment will demonstrate a dramatic example of gene expression changes in the life of an organism. More generally, the identification of common loci underlying parasitic growth across diverse plant parasites, will facilitate the development of genetic tools to tackle parasitic plants that grow as agricultural pests.