Project Summary SARS-CoV-2 is responsible for the global COVID-19 pandemic. In addition to acute symptoms such as respiratory failure and other flu-like symptoms, this virus has been more recently implicated in numerous chronic symptoms, which are collectively referred to as Post-Acute Sequelae of COVID-19 (PASC, also known as ‘long COVID’). Many symptoms of PASC are related to the nervous system, such as cognitive dysfunction, brain fog, memory loss, sensory problems, depression, anxiety and insomnia. Compared to our understanding on how SARS-CoV-2 causes severe acute symptoms of COVID-19, the mechanism by which this virus causes PACS is not well understood. To facilitate the study of COVID-19 and PASC, we have been generating three types of genetic reagents in the fruit fly Drosophila melanogaster. The first is a collection of transgenic flies that allows conditional expression of single viral proteins in a cell-type or time specific manner. The second is a series of transgenic flies that allows conditional expression of individual human proteins that have been found to physically interact with one of the SARS-CoV-2 proteins. The third is a collection of versatile gene-trap lines that allow one to investigate the loss-of-function phenotype and expression pattern of the fly gene that correspond to one of the SARS-CoV-2 human interactors. Scientists can combine these three types of reagents to perform sophisticated experiments to study whether the viral and human proteins functionally interact in a living organism, or whether the function of the homologous genes in fly and human share the same molecular function in vivo. In this study, we propose to further expand our research toolkit to complete the collection. In addition, we will perform in vivo characterization of the reagents generated so far to provide phenotypic and gene expression information to facilitate the use of these reagents in the research community. These genetic tools are or will be publicly available through the Drosophila Bloomington Stock Center and the information collected will be documented in FlyBase. This collection of transgenic and mutant flies will greatly facilitate the in vivo characterization of proteins encoded in the SARS-CoV-2 genome and its interactors,. It will therefore provide valuable information to combat COVID- 19 and PASC.