P008
Living on the edge – mitochondrial morphology throughout
the T. gondii lytic cycle
Jana Ovciarikova1, Wes MacDonald2 and Lilach Sheiner1
1
University of Glasgow, Glasgow, UK
2
University of Arizona, Tucson, USA
Over the course of evolution mitochondrial behavior inside
eukaryotic cells has changed extensively, and the machineries
that underly these adaptations have in many cases developed
in organism-specific ways. As a result, different mechanisms
control mitochondrial motility and shape in a way that serves
the varied functions within different cells. We set out to explore
mitochondrial behaviour in T. gondii as the necessary first step to
elicit the form-function relationship of this extremely understudied organelle. A previous study describes unusual mitochondrial
behaviour during T. gondii tachyzoite cell division, whereby mitochondria remain excluded from the growing daughters until the
very end of cytokenesis when the organelles are rapidly inserted
into the daughters. We cloned a new fluorescent marker for the
mitochondrial outer membrane and used it in super-resolution
and time-lapse microscopy to assess mitochondrial morphology
under various conditions. Specifically we examined mitochondria
in several mutants with biogenesis defects in other organelles,
and under Orysalin treatment. Our observations support the
hypothesis previously put forward that the mitochondrion in T.
gondii is tethered to the inner membrane complex, which may
explain its behaviour during cell division. We then extended the
examination of mitochondrial behavior to ask whether tethering
persists throughout the lytic cycle, and especially when the
parasites are motile or invading host-cells. We were surprised
to observe a tight correlation between loss-of-thethering and
reduced parasite fitness.