PROJECT SUMMARY Candida albicans is both a commensal component of the normal human microbial flora and an important human pathogen. Although the commensal niches occupied by C. albicans are primarily limited to the gastrointestinal and genitourinary tracts, candidal disease, in contrast, can involve a wide range of organ systems including kidney, spleen, liver, heart, eye, the central nervous system, and skin/mucosae. As such, C. albicans is a versatile pathogen that adapts to a wide range of physiologically diverse environments within the human host. Understanding the systems that facilitate this adaptation is central to developing detailed mechanistic models of C. albicans pathogenesis and could inform the identification of new therapeutic approaches to candidiasis. To date, C. albicans transcription factors (TF) are the best characterized components of this system, due in part to the availability of comprehensive sets of TF deletion mutants. In contrast, upstream regulators of C. albicans physiology such as protein kinases (PK) have not been systematically studied to the same extent. To address this knowledge gap, the long-term goal of our project is to systematically characterize the role of PKs in C. albicans pathobiology. As a first step toward this goal, we propose to: 1) generate and validate a barcoded set of homozygous and heterozygous C. albicans PK deletion mutants using a transient CRISPR/Cas9 strategy; 2) Systematically characterize the PK deletion mutants in two murine model of candidiasis and two virulence relevant in vitro processes: biofilm and hyphae formation; 3) Identify and characterize the network of PK-TF pairs that regulate biofilm and hyphae formation using genetic interaction analysis. Successful completion of these aims will provide a useful genetic resource for the research community, provide the first systematic functional characterization of C. albicans PKs in vivo and in vitro, and set the stage for subsequent in-depth analyses of the genetic networks regulated by C. albicans PKs.