De Novo Genome Sequence Assembly of the RNAi-Tractable Paramecium bursaria 186b: An Endosymbiotic Model System.

How two species engage in stable endosymbiosis is a biological quandary. The study of facultative endosymbiotic interactions has emerged as a useful approach to understand how endosymbiotic functions can arise. The ciliate protist Paramecium bursaria hosts green algae of the order Chlorellales in a facultative photo-endosymbiosis. We have recently reported RNAi as a tool for understanding gene function in P. bursaria 186b (CCAP strain 1660/18). To complement this work, here we report a near complete host genome and transcriptome sequence dataset, using both Illumina and PacBio sequencing methods, in order to aid genome analysis and to enable the design of RNAi experiments. Our analyses demonstrate P. bursaria 186b, like other ciliates such as diverse species of Paramecia, possess numerous tiny introns. These data patterns, combined with the alternative genetic code common to ciliates, make gene identification and annotation challenging; as such, we identify gene models using Iso-Seq methodologies. These data will aid the investigation of genome evolution in the Paramecia and provide additional source data for the exploration of endosymbiotic functions.