Proximity biotinylation of the Toxoplasma gondii basal complex

During T. gondii cell division (endodyogeny) the basal complex acts as the cytokinetic ring by preserving daughter bud integrity and executing the tapering and basal constriction of nascent parasites. Its molecular composition, order of assembly and mode of action are incompletely understood but differ substantially from final cytokinesis events described in other organisms. In order to identify new proteins of the basal complex we used proximity biotinylation (BioID) and fused the small biotin ligase BioID2 (Kim et al., 2016) to basal complex components (BCCs). We endogenously tagged MORN1, Centrin2 (Cen2), IMC8, MyoJ, BCC1 (TGGT1_232780) and BCC2 (TGGT1_231070) with BioID2 and used an YFP-BioID2 fusion protein as a cytosolic control. Our reciprocal BioID approach identifies several novel BCCs that resolve into four basal complex sub clusters (BCSC1-4). Together with the functional characterization of critical BCCs our data uncover a novel dimension to the hierarchy and structure of daughter budding.