Mitochondrial behaviour throughout the lytic cycle of Toxoplasma gondii

Abstract

Mitochondria distribution in cells controls cellular physiology in health and disease. Here we describe the mitochondrial morphology and positioning found in the different stages of the lytic cycle of the eukaryotic single-cell parasite Toxoplasma gondii. The lytic cycle, driven by the tachyzoite life stage, is responsible for acute toxoplasmosis. It is known that whilst inside a host cell the tachyzoite maintains its single mitochondrion at its periphery. We found that upon parasite transition from the host cell to the extracellular matrix, mitochondrion morphology radically changes, resulting in a reduction in peripheral proximity. This change is reversible upon return to the host, indicating that an active mechanism maintains the peripheral positioning found in the intracellular stages. Comparison between the two states by electron microscopy identified regions of coupling between the mitochondrion outer membrane and the parasite pellicle, whose features suggest the presence of membrane contact sites, and whose abundance changes during the transition between intra- and extra-cellular states. These novel observations pave the way for future research to identify molecular mechanisms involved in mitochondrial distribution in Toxoplasma and the consequences of these mitochondrion changes on parasite physiology.

Identification of the Toxoplasma gondii mitochondrial ribosome, and characterisation of a protein essential for mitochondrial translation

“…In model organisms, mitochondrial morphology and function are tightly linked. In support of this also being the case in Toxoplasma, recent studies reported rapid mitochondrial remodelling in respond to drastic changes in the growth environments (Charvat and Arrizabalaga, 2016;Ovciarikova et al, 2017). The morphological defect observed here upon TgmS35 depletion provides additional support (Fig.…”

“…Ke et al, 2018;Seidi et al, 2018) and on fluorescence microscopy analysis using fluorescent dyes (e.g. Vercesi et al, 1998;Garbuz and Arrizabalaga, 2017;Ovciarikova et al, 2017) for mitochondrial functional studies. Here, we developed an organelle enrichment protocol which generates high-quantity fractions enriched with active mitochondria that can be used to investigate the activity of mitochondrial pathways in vitro.…”

“…Coverslips were washed as above and mounted on microscope slides using DAPI-fluoromountG (Southern Biotech). Images were taken using a Delta Vision microscope as described (Ovciarikova et al, 2017).…”

TgDrpC, an atypical dynamin‐related protein in Toxoplasma gondii, is associated with vesicular transport factors and parasite division

“…During this process, specialized secretory organelles (dense granules, micronemes, and rhoptries) are synthesized de novo from the Golgi within the forming daughter cells. Finally, the single mitochondrion from the mother enters each developing daughter parasite (Ovciarikova et al , ).…”

Localization of Fe‐S Biosynthesis Machinery in Cryptosporidium parvum Mitosome

“…more plausible, since it is not unusual for apicomplexan parasites. For example, the morphology of Toxoplasma mitochondria changes radically during the transition of the parasite from the host cell to the extracellular matrix (Ovciarikova et al 2017). The mitochondria of Plasmodium falciparum grow from single, small, discrete organelles into highly branched structures in the later stages of its life cycle (van Dooren et al 2005).…”