Apicortin defines the Plasmodium apical conoid body but is dispensable for the parasite life cycle

Apicomplexan parasites such as Plasmodium spp. and Toxoplasma gondii possess unique tubulin-based structures, including subpellicular microtubules and apical polar rings, which are essential for parasite motility, host cell invasion, and replication. Apicortin, a microtubule-associated protein, contains a doublecortin (DC) domain and a partial t ubulin p olymerization- p romoting p rotein (TPPP) domain, both implicated in microtubule binding and stabilization. How tubulin-based structures are maintained is poorly understood, but it may involve Apicortin, so far found only in apicomplexans and the placozoan Trichoplax adhaerens . Here, we investigated the location and function of Apicortin in Plasmodium berghei . Live-cell imaging of a transgenic parasite line expressing GFP-tagged Apicortin showed its location at the apical end of invasive parasite stages within the mosquito vector. Super-resolution and expansion microscopy revealed that Apicortin forms a distinct ringlike structure in the apical complex region at the apical end. However, deletion of the Apicortin gene had no effect on parasite development, indicating that this protein is not essential. This suggests that there may be redundancy or compensatory functions in the mechanisms that stabilize the apical complex.