PROJECT SUMMARY Molecular cell death pathways are being extensively studied in mammalian cells. These genetically regulated cell death processes are critical for maintenance of human health, defense against infection and for successful cancer therapy, but their deregulation underlies disease pathology. Considerable progress towards delineating the molecular details has yielded successful designer drugs now entering the clinic, such as venetoclax that specifically targets anti-apoptotic BCL2 to trigger tumor cell death. In contrast, analogous approaches are not available for triggering intrinsic cell death pathways encoded by human pathogens such as fungi, bacteria and parasites because very little is known about the basic biology. The near complete lack of understanding of the relevant events in dying microbial cells is surprising given their importance as human pathogens. For example, fungal pathogens pose an increasing threat to public health, claiming 1.5 million lives annually worldwide. The long-standing assumption that microbial cells do not encode such intrinsic death pathways has delayed advancements in this direction. However, new rigorous evidence from multiple sources argues strongly in favor, and partially delineated death pathways in multi-cellular fungi provide additional compelling support. Here we propose to map the first molecularly defined death pathway in a single-cell fungal/yeast species, the laboratory workhorse Saccharomyces cerevisiae (Aim 1), and to initiate studies that extend this knowledge to a single-cell human fungal/yeast pathogen Cryptococcus neoformans, a major public health burden (Aim 2).