Authors

Discussion

The photosynthetic flagellate Euglena gracilis harbours a secondary endosymbiotic plastid and is a distant relative of pathogenic trypanosomatids, a major component of global aquatic ecosystems and of considerable biotechnological potential with resistance to harsh conditions. Here we report genome, transcriptome and proteome drafts for E. gracilis. The genome is over 2Gb and has a coding potential of 36,526 predicted ORFs. Less than 25% of the genome is single copy sequence, indicating extensive repeat elements. Several gene families likely associated with the cell surface and signal transduction possess very large numbers of lineage-specific paralogs, suggesting great flexibility in environmental monitoring and, together with divergent mechanisms for metabolic control, novel solutions to adaptation to extreme environments. There are clear contributions from photosynthetic eukaryotes to the nuclear genome with red, green and brown algael genes evident, together with orthogroups shared with only trypanosomes and also with other excavates. Furthermore, we demonstrate that the majority of control of protein expression level is post-transcriptional despite the presence of conventional introns, that mRNA metabolism is highly unusual in transcriptional and nuclear export mechanisms and which differentiate Euglenids from the trypanosomatids. These data are a major advance in the understanding of the nuclear genome of Euglenids and provide a platform for investigation of the contributions of Euglena gracilis and relatives to the biosphere.