School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK.
Department of Biochemistry, University of Cambridge, Cambridge, CB2 1QW, UK.
BMC Biol. 2019 Feb 7;17(1):11. doi: 10.1186/s12915-019-0626-8.
Photosynthetic euglenids are major contributors to fresh water ecosystems. Euglena gracilis in particular has noted metabolic flexibility, reflected by an ability to thrive in a range of harsh environments. E. gracilis has been a popular model organism and of considerable biotechnological interest, but the absence of a gene catalogue has hampered both basic research and translational efforts.
We report a detailed transcriptome and partial genome for E. gracilis Z1. The nuclear genome is estimated to be around 500 Mb in size, and the transcriptome encodes over 36,000 proteins and the genome possesses less than 1% coding sequence. Annotation of coding sequences indicates a highly sophisticated endomembrane system, RNA processing mechanisms and nuclear genome contributions from several photosynthetic lineages. Multiple gene families, including likely signal transduction components, have been massively expanded. Alterations in protein abundance are controlled post-transcriptionally between light and dark conditions, surprisingly similar to trypanosomatids.
Our data provide evidence that a range of photosynthetic eukaryotes contributed to the Euglena nuclear genome, evidence in support of the 'shopping bag' hypothesis for plastid acquisition. We also suggest that euglenids possess unique regulatory mechanisms for achieving extreme adaptability, through mechanisms of paralog expansion and gene acquisition.
光合腰鞭毛虫是淡水生态系统的主要贡献者。特别是绿色眼虫具有显著的代谢灵活性，能够在多种恶劣环境中茁壮成长。绿色眼虫一直是一种受欢迎的模式生物，具有相当大的生物技术兴趣，但由于缺乏基因目录，既妨碍了基础研究，也妨碍了转化工作。
我们报告了绿色眼虫 Z1 的详细转录组和部分基因组。核基因组估计约为 500Mb 大小，转录组编码超过 36000 种蛋白质，基因组的编码序列不到 1%。编码序列的注释表明，它具有高度复杂的内膜系统、RNA 处理机制以及来自几个光合谱系的核基因组贡献。包括可能的信号转导成分在内的多个基因家族已经大规模扩张。在光照和黑暗条件下，通过转录后控制改变蛋白质丰度，与原生动物门非常相似。
我们的数据提供了证据表明，一系列光合真核生物为 Euglena 核基因组做出了贡献，支持了质体获取的“购物袋”假说。我们还表明，眼虫通过基因扩张和基因获取的机制，拥有独特的调节机制来实现极端的适应性。
