Key result
Electron microscopy and tomography revealed that the cytostome-cytopharynx complex disassembles during late G2 and M phases, with the microtubule quartet likely guiding new assembly.
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The cytostome-cytopharynx complex is the main site for endocytosis in epimastigotes of Trypanosoma cruzi It consists of an opening at the plasma membrane surface - the cytostome - followed by a membrane invagination - the cytopharynx. In G1/S cells, this structure is associated with two specific sets of microtubules, a quartet and a triplet. Here, we used electron microscopy and electron tomography to build 3D models of the complex at different stages of the cell cycle. The cytostome-cytopharynx is absent in late G2 and M phase cells, whereas early G2 cells have either a short cytopharynx or no visible complex, with numerous vesicles aligned to the cytostome-cytopharynx microtubules. The microtubule quartet remains visible throughout cell division (albeit in a shorter form), and is duplicated during G2/M. In contrast, the microtubule triplet is absent during late G2/M. Cells in cytokinesis have an invagination of the flagellar pocket membrane likely to represent early stages in cytostome-cytopharynx assembly. Cells in late cytokinesis have two fully developed cytostome-cytopharynx complexes. Our data suggest that the microtubule quartet serves as a guide for new cytostome-cytopharynx assembly.
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Alcantara et al. (2016) studied Trypanosoma cruzi epimastigotes. Electron microscopy and electron tomography was evaluated on 3D models of the cytostome-cytopharynx complex at different stages of the cell cycle. Electron microscopy and tomography revealed that the cytostome-cytopharynx complex disassembles during late G2 and M phases, with the microtubule quartet likely guiding new assembly.
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