Morphogenesis of many protozoans depends on a polarized establishment of cortical cytoskeleton containing the subpellicular microtubules (SPMTs), which are apically nucleated and anchored by the apical polar ring (APR). In malaria parasite Plasmodium , APR emerges in the host-invading stages, including the ookinete for mosquito infection. So far, the fine structure and molecular components of APR as well as the underlying mechanism of APR-mediated apical positioning of SPMTs are largely unknown. Here, we resolve an unprecedented APR structure composed of a top ring plus approximate 60 radiating spines. We report an APR-localizing and SPMT-binding protein APR2. APR2 disruption impairs ookinete morphogenesis and gliding motility, leading to Plasmodium transmission failure in mosquitoes. The APR2-deficient ookinetes display defective apical anchorage of APR and SPMT due to the impaired integrity of APR. Using protein proximity labeling, we obtain a Plasmodium ookinete APR proteome and validate ten undescribed APR proteins. Among them, APRp2 and APRp4 directly interact with APR2 and also mediate the apical anchorage of SPMTs. This study sheds light on the molecular basis of APR in the organization of Plasmodium ookinete SPMTs. The structure of subpellicular microtubules (SPMTs) nucleated from the apical polar ring (APR) is essential for Plasmodium parasite morphogenesis, gliding motility, and invasion. Here, Qian et al. characterize the function of APR2 protein in P. yoelii ookinetes. Using co-localization analysis, proximity labeling, CoIP, expansion microscopy and FRAP, they show that APR2 binds to SMPTs and has a fixed position in APR. Deletion mutants fail to traverse the mosquito midgut as they fail to anchor SPMTs on APR, which affects invasive morphology and gliding motility.
【저자키워드】 Parasite biology, Parasite development,