Partitioning of Giardia central mitosomes during mitosis. A The schematic drawing of Giardia trophozoite depicts central and peripheral mitosomes (red). The first are found between two nuclei, where also basal bodies and axonemes of Giardia flagella are localized. The latter are scattered across cytoplasm. There are four pairs of flagella called according to their position in the cell as anterolateral (light blue), posterolateral (dark green), ventral (light green), and caudal (dark blue). Additionally, the helical sheet of microtubules forms the adhesive disc of Giardia (gray). Immunofluorescence microscopy image of mitosomes labeled by anti- GL50803_9296 antibody (red), anti-β-tubulin. Merged image on the right includes nuclei stained with DAPI. The inlet is DIC image of the cell. B Giardia expressing the fusion of targeting presequence of mitosomal GrpE and Y-FAST were enriched for mitotic cells using albendazole treatment and incubated with 4-hydroxy-3-methylbenzylidene-rhodanine (HMBR) substrate. The reversible binding of Y-FAST to the fluorogenic substrate induces its green fluorescence (530–540 nm) upon excitation at 470–480 nm. The observed plane was focused on the central mitosomes. The series of images demonstrates fast partitioning of the fluorescence corresponding to central mitosomes. Red arrowheads highlight the position of central mitosomes. C The size of the fluorescent signal corresponding to the central mitosomes in the interphase and mitotic cells (the averaged values of 30 cells are shown). The scale bars 2 μm.