Plasmodium actin-like proteins are essential for DNA segregation during male gametogenesis and malaria transmission

Protozoan parasites of the genus Plasmodium cause malaria and involve infection of multiple hosts and cell types during the life cycle. Producing sexually fit gametocytes is essential for transmitting the Plasmodium parasite into an anopheline mosquito vector. After the uptake of malaria parasites, male gametocytes undergo three rounds of DNA replication to produce eight nucleated flagellar gametes. Here, we report that the actin-like proteins Alp5a and Alp5b are involved in DNA segregation during male gametogenesis. The Plasmodium -specific paralogous genes Alp5a and Alp5b superimposed on human Arp2 and Arp3, localize to the nucleus, and interact with each other. Alp5a and Alp5b are dispensable for the development of P. berghei blood-stages individually but indispensable simultaneously. In agreement with genetic studies, the inhibitory activity of the Arp2/3 complex inhibitor in Plasmodium supports an essential role for this complex during the blood stage. Deletion of Alp5a or Alp5b did not affect actin nucleation, parasite growth, or gametocytemia in the blood. The knockout parasites successfully invaded the midgut and developed into oocysts, but their size was significantly reduced, and they failed to survive. Genetic crosses revealed defects in male gamete integrity. We found that the reduced oocyst development was due to impaired DNA segregation during male gametogenesis. This study provides molecular insight into the fundamental requirements of the Alps in Plasmodium , which are essential for malaria transmission.