Global climate change is projected to increase the spread of fungal infectious diseases due to persistent stressful environmental conditions, such as record-breaking hot temperatures and droughts. Because pathogenic fungi are good at tolerating stress, they may thrive under environmental stressful conditions compared to other non-pathogenic fungi. The objective of this proposal is to investigate the relationship between fungal pathogenicity and climate change. Specifically, if stress-tolerance brought by global climate change triggers pathogenicity in soil fungi. The central hypothesis is that exposure to chronic environmental stressors, such as heat and drought, favors the proliferation of pathogenic fungi in soil fungal communities and enhances their stress-tolerance and pathogenicity. The rationale of this hypothesis is that upon completion of this project, we will have identified mechanisms to better understand the relationship between climate change and pathogenicity. Consequently, this will allow us to better plan for potential outbreaks of fungal infectious diseases under global climate change, develop contingency plans, and potential treatments. The central hypothesis will be tested by pursuing three specific aims: 1) Assess if stressful chronic conditions from climate change, such as heat and drought, favor pathogenic fungi over non-pathogenic fungi in soils; 2) Determine if heat and drought trigger saprotroph-to-pathogen transformations in fungi; 3) Evaluate if exposure to chronic heat and drought cause persistent physiological changes in fungi including increased stress-tolerance and pathogenicity. We will pursue these aims using an innovative and multi-scale approach which lies at the intersection of microbiology, climate change, and public health. It includes the use of traditional microbiological techniques coupled with recently developed high-throughput sequencing and bioinformatic tools. These will be applied at the species and community level to assess short- and long-term responses. The proposed research is significant because investigating how fungi are responding and adjusting to global climate change is vital for understanding and predicting future fungal disease outbreaks. The expected outcome of this work is to obtain comprehensive knowledge of the changes the soil fungal community undergoes when exposed to chronic heat and drought. In addition, to better understand fungal resource investment under stressful environmental conditions, including physiological responses underlying pathogenicity in wild fungal communities at multiple scale. The results of this project will have a positive impact immediately because it will provide knowledge into pathogenicity mechanisms that fungi undergo when exposed to stressful conditions. Therefore, my work will: 1) provide foundational knowledge to model and predict future fungal disease outbreaks and 2) inform policy makers on the public health threat potential that climate change has on ...