The Euglena Genome Project

AbstractBackground: Photosynthetic euglenids are major contributors to fresh and salt water ecosystems. Euglena gracilis in particular has noted metabolic flexibility, reflected by an ability to exploit a range of harsh environments. E. gracilis has been a popular model organism and of considerabe biotechnological interest, but the absence of a gene catalogue has hampered both basic research and translational efforts.Results: We report a detailed transcriptome and partial genome for E. gracilis Z1. Remarkably, the nuclear genome is estimated to exceed 2Gb, encode 36 526 proteins and possess less than 1% coding sequence. Annotation of coding sequences indicates a highly sophisticated endomembrane system, RNA processing capacity and nuclear genome contributions from several photosynthetic lineages. Multiple gene families, including likely signal transduction components, have been massively expanded. Alterations to protein abundance are controlled post-transcriptionally between light and dark conditions, surprisingly similar to trypanosomatids.Conclusions: These 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.