An atypical Arp2/3 complex is required for Plasmodium DNA segregation and transmission of malaria.

Plasmodium parasites, the causative agents of malaria, undergo crucial developments within the mosquito vector, initiated by the formation of male and female gametes from gametocytes. Male gametogenesis involves three rapid rounds of endomitosis followed by a single round of DNA segregation and nuclear division during gamete budding. How the cell organises the segregation of eight genomes from a single octoploid nucleus into eight haploid gametes is currently unknown. Here, we discovered an atypical five-subunit Arp2/3 complex in Plasmodium important for correct DNA segregation during male gametogenesis. Unlike the canonical seven-subunit Arp2/3 complex found in other eukaryotes, Plasmodium Arp2/3 localizes to endomitotic spindles and interacts with a kinetochore-associated protein. Disruption of key Arp2/3 subunits or actin polymerization interferes with kinetochore-spindle association, resulting in the formation of sub-haploid gametes and halting transmission. Our work identified an evolutionary divergent Arp2/3 protein complex in malaria parasites, offers novel insights into gametogenesis, and uncovers potential targets for transmission-blocking interventions.