Parasite replication dynamics

Protozoa in the phylum Apicomplexa replicate using a distinctive process in which multiple progeny are assembled within the mother, using a membrane–cytoskeletal scaffolding known as the inner membrane complex (IMC). Parasite pathogenesis is a direct consequence of uncontrolled replication, so understanding this process is of great importance, but little is known about the dynamics of IMC assembly and degradation. Now, Dinkorma Ouologuem and David Roos (p. 3320) exploit live-cell imaging of fluorescently tagged marker proteins to monitor the dynamics of IMC biogenesis and turnover in replicating Toxoplasma gondii tachyzoites. The authors used the integral IMC protein GAP40 to define four distinct developmental stages: initiation, elongation, emergence and maturation. Time-lapse video microscopy in combination with photobleaching and photoactivation revealed de novo synthesis during elongation of the daughter IMC, but salvage and recycling of the maternal IMC during post-emergence maturation. This work establishes the basis for future investigation of IMC trafficking and turnover, including the rapid degeneration observed during Plasmodium merozoite differentiation. The apicomplexan IMC also provides an intriguing target for new therapeutic strategies.