Fig. 1. Visualization of the flagella connector at the distal tip of the new flagellum. (A) The cell cycle of procyclic trypanosomes. At G1, trypanosomes posses a single kinetoplast and a single nucleus (1K1N) with a single attached flagellum. During the cell cycle, new flagellum elongation coincides with kinetoplast duplication and segregation (2K1N). The new flagellum is physically attached to the old flagellum via the flagella connector. Following mitosis (2K2N) and the initiation of cytokinesis, this connection is released. (B-D) Negatively stained whole-mount cytoskeletons of procyclic trypanosomes. (B) The flagella connector (asterisk) is positioned at the tip of the new flagellum (nf) and along the side of the axoneme (ax) of the old flagellum (of) and not the paraflagellar rod (pfr). (C) The flagella connector consists of a trilaminar core structure composed of three distinct layers of electron density (layers 1,2,3) and filamentous extensions (marked with a bar) extending to the tip of the new flagellum. This gives roughly an overall triangular appearance. (D) No flagella connector structure is evident at the tip of the old flagellum. Scale bars, 200 nm (B), 100 nm (C,D).