Researchers have discovered that parasites of the Apicomplexa taxon, such as Plasmodium falciparum and Toxoplasma gondii, reproduce within host cells using a structure that evolved from a flagellum.
Notably, the team also found that genetic disruption of the structure of this fiber prevented successful replication taking place in T. gondii.
"These altered parasites can initially infect cells, but once we turn off the fiber genes, they cannot create new daughter cells and spread," explained study author Maria Francia, from the University of Georgia, Athens, USA, in a press statement. "Since it cannot replicate, the parasite eventually dies without causing serious harm."
Protists of the Apicomplexa taxon evolved from single-celled flagellated algae, although only the gametes have flagella.
Boris Streipen, also from the University of Georgia, and colleagues found that these parasites form daughter cells through the end of a fiber-like structure, formed from striated fiber assemblins (SFAs). They believe this fiber acted as the base of the flagella - a tail-like structure that enabled a swimming motion - in the algal ancestor of modern-day Apicomplexa species.
"This was a surprising finding," said Striepen. "These parasites no longer use flagella to swim, but they have apparently now repurposed this machinery to organize the assembly of an invasive cell."
The investigators carried out genetic experiments on T. gondii to assess whether this replication process could be disrupted.
They found that if the proteins TgSFA2 and TgSFA3 were absent the formation of daughter cells was blocked at an early stage. Mitosis continues to occur in these cells, and many nuclei are accumulated, but no viable daughter cells are formed.
"It is extremely important to understand the evolution of different organisms, but especially the evolution of pathogens," commented Striepen.
"The analysis of their evolution produces important opportunities to develop treatments, but it also helps us understand the basic structures of the pathogens that we must fight."
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