PROJECT SUMMARY Malaria remains a major global infectious disease, largely affecting people living in resource poor environments. Infection of humans with Plasmodium falciparum parasites results in significant morbidity and mortality. Drug- resistance is constantly undermining the usefulness of antimalarial regimens. It is imperative to identify new antimalarial drug targets to ensure the success of control and eradication efforts. Further, the call for malaria eradication requires an understanding of the determinants of parasite transmission. Plasmodium falciparum parasites utilize epigenetic machinery for the regulation of key processes within the parasitic life-cycle, including antigenic variation for persistence and pathogenesis during asexual proliferation, as well as for switching to sexual development for transmission through the parasitic life-cycle. We have obtained genetic evidence that the Class II histone deacetylases (HDACs) are essential for P. falciparum growth during the asexual cycle. We hypothesize that these P. falciparum HDACs regulate discrete and critical functions in the asexual and sexual biology of the parasite. Inhibition of these mechanisms will result in the specific killing of P. falciparum asexual and/or sexual forms. In this proposal, we will identify the essential functions of these enzymes that are responsible for asexual proliferation, conversion to the sexual stage, and sexual development for transmission. We will use a reverse genetics approach for the phenotypic analysis of mutant parasites in the asexual and sexual stages. We will probe the mechanistic basic of HDAC functions using a combination of bulk and single cell transcriptomics and epigenomics. Finally, we will uncover the precise mechanisms of action of the HDACs by dissecting the functions of their specific enzymatic domains, using biochemical and chemical genetic approaches. Together, these studies will serve to elucidate the functions of these critical epigenetic regulators in parasite biology relevant to asexual proliferation for virulence and sexual development for transmission, validating and characterizing these molecules as new targets for therapeutic development within the parasite.