Malaria symptoms occur once the parasite's asexual stages begin replicating inside red blood cells. However, these asexual forms must transform into male and female stages called gametocytes in order to infect the mosquitoes that spread the disease. Investigators now report they have identified a protein called HDP1 that plays a critical role in activating genes required for the development of these male and female stages. The finding provides important new insights into how the parasite controls this conversion into gametocytes.