bioRxiv preprint doi: https://doi.org/10.1101/2020.12.16.423098; this version posted December 16, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. Validation of a Core RNA-interference Pathway as a Tool for Reverse Genetics in the Emergent Model Phototrophic Endosymbiosis, Paramecium bursaria Benjamin H. Jenkins1,2*, Finlay Maguire3*, Guy Leonard1,2, Joshua D. Eaton1, Steven West1, Benjamin E. Housden1, David, S. Milner1,2, & Thomas A. Richards1,2* 1Living Systems Institute and Biosciences, University of Exeter, Devon EX4 4QD, UK 2Department of Zoology, University of Oxford, 11a Mansfield Road, Oxford OX1 3SZ, UK 3Faculty of Computer Science, Dalhousie University, 6050 University Ave, Halifax NS B3H 1W5, Canada *Correspondence:
[email protected] &
[email protected] KEYWORDS Paramecium bursaria, algae, symbiosis, RNAi, Dicer, Argonaute, Pds1, siRNA ABSTRACT Endosymbiosis was fundamental for the evolution of eukaryotic cellular complexity. The genetic basis of an emergent endosymbiotic interaction may be investigated using forward and reverse genetic techniques, such as RNA-interference (RNAi). However, distinguishing small (s)RNA processing pathways in a eukaryote-eukaryote endosymbiotic interaction is complex. Here, we investigate the repertoire of candidate RNAi pathway protein-encoding genes in the model nascent endosymbiotic system, Paramecium bursaria–Chlorella spp. Using comparative genomics and transcriptomics supported by phylogenetics, we identify putative essential proteome components of the small interfering (si)RNA, scan (scn)RNA, and internal eliminated sequence (ies)RNA pathways encoded by P.