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Fig. 7 | BMC Biology

Fig. 7

From: Giardia intestinalis mitosomes undergo synchronized fission but not fusion and are constitutively associated with the endoplasmic reticulum

Fig. 7

The evolution of mitochondrial dynamics in Excavata. A schematic representation of the occurrence of the mitochondrial fission and fusion machinery and the endoplasmic reticulum (ER)–mitochondria tethering complexes. The patchy phylogenetic distribution of FtsZ-based machinery [19] suggests that dynamin-based division of mitochondria appeared later in the evolution of eukaryotes and was not present in the last eukaryotic common ancestor (LECA). While both systems can be found in Excavata, G. intestinalis does not use either of them for the division of mitosomes. The lack of observable mitochondrial fusion and the responsible molecular machinery in Excavata indicates that the lack of fusion is an ancestral trait. The components of both recently described ER-tethering complexes can be found in all five supergroups of eukaryotes and thus they were likely present in the LECA [76]. Despite the secondary loss of these complexes, G. intestinalis mitosomes maintain association with the ER throughout the cell cycle, indicating the presence of yet unknown tethering mechanisms, perhaps including lipid metabolism enzymes such as LACS4. ERMES endoplasmic reticulum–mitochondria encounter structure, EMC endoplasmic reticulum membrane protein complex

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