Unlocking the Mysteries of Plastid Origin Through Comparative Genomic Analysis of Two Paulinella Species

真核生物获得光合作用是进化中的一个关键事件，因为藻类和植物构成了地球生命食物链的基础。质体（例如，叶绿体），藻类和植物中的光合作用机器，通过初级内共生，获得以前自由生活的光合细菌，具有蓝细菌起源。 藻类和植物中质体进化的知识是有限的，因为主要的内共生事件发生在十亿多年前。Paulinella chromatophora是一种绿色变形虫，这是值得注意的，因为它最近获得了一个质体通过一个独立的初级内共生涉及原绿球藻或聚球藻样蓝藻。近缘的Paulinella ovalis缺乏质体，但以蓝藻为食。使用这些模式生物，该项目将1）使用最现代的高通量焦磷酸测序方法对光合变形虫Paulinella chromatophora的基因组DNA进行测序并生成转录组数据库，并对缺乏质体的Paulinella ovalis的基因组DNA进行测序，2）比较P. chromatophora和P. ovalis之间的基因库存，3）向公众免费提供Paulinella基因组序列。光合自养P. chromatophora和异养P. ovalis之间的基因组比较将使研究人员能够在两种密切相关的生物中生成基因/基因组目录，一种具有和一种不具有初级内共生质体。 这应该能够识别允许初级质体建立的初始基因组创新，即允许从异养（动物）过渡到自养（植物）的关键过程。这些基因组数据有可能应用于基因工程领域。该项目将支持来自代表性不足群体的本科生和博士后研究助理的培训。项目结果将发表在科学论文中，并将在基因组学研讨会上进行讨论。 该研讨会将借鉴来自美国和世界各地的基因组专家的专业知识，并将包括学生的积极参与。本次研讨会的目的是促进内共生和原生生物基因组学的理解。

The acquisition of photosynthesis by eukaryotes was a pivotal event in evolution because algae and plants form the base of the food chain for life on Earth. Plastids (e.g., chloroplasts), the machines of photosynthesis in algae and plants, have a cyanobacterial origin through primary endosymbiosis, the acquisition of a formerly free-living photosynthetic bacterium. Knowledge of plastid evolution in algae and plants is limited because the primary endosymbiotic event occurred more then a billion years ago. Paulinella chromatophora is a green amoeba that is remarkable because it very recently acquired a plastid via an independent primary endosymbiosis involving a Prochlorococcus or Synechococcus-like cyanobacterium. The closely related Paulinella ovalis lacks a plastid but feeds actively on cyanobacteria. Using these model organisms, this project will 1) sequence genomic DNA and generate a transcriptome database from the photosynthetic amoeba Paulinella chromatophora and sequence genomic DNA from the plastid-lacking Paulinella ovalis using the most modern high-throughput pyrosequencing methods, 2) compare the gene inventories between P. chromatophora and the P. ovalis, and 3) make freely available to the public the Paulinella genome sequences. Genome comparisons between the photoautotrophic P. chromatophora and the heterotrophic P. ovalis will allow the researchers to generate a gene/genome catalogue in two closely related organisms, one with and one without a primary endosymbiotic plastid. This should enable the identification of initial genomic innovations that allowed primary plastid establishment, that is, the critical process that allowed a transition from heterotrophy (animal) to autotrophy (plant). These genomic data could potentially be applied to the field of genetic engineering. This project will support training of undergraduates and post-doctoral research associates from underrepresented groups. The project results will be published in scientific papers and they will be discussed in a genomics workshop. The workshop will draw upon expertise from genome specialists from the US and worldwide and it will include active student participation. The goal of this workshop will be to advance understanding of endosymbiosis and protist genomics.