BRC-BIO: the molecular basis for carbon dioxide sensing and response in dimorphic fungi

This federal Project Grant award from the National Science Foundation (NSF) Biological Sciences program (CFDA 47.074) provides $502,946 to Rhodes College to investigate the molecular mechanisms by which dimorphic fungi sense and respond to changes in carbon dioxide levels. The project aims to genetically and biochemically characterize the carbonic anhydrases in the model fungus Histoplasma capsulatum, which facilitate the interconversion of carbon dioxide and water. Through genetic screening, DNA pulldown assays, and RNA-sequencing, the project will identify novel cellular components involved in carbon dioxide sensing, with the goal of advancing the understanding of how fungi adapt to environmental cues. The award supports undergraduate research opportunities at Rhodes College and LeMoyne-Owen College, including a course-based research experience. The project period runs from June 15, 2024, to May 31, 2027.

Abstract

This project will seek to understand how dimorphic fungi sense and respond to the shift of carbon dioxide concentration in the environment. Dimorphic fungi are a group of microorganisms that switch between two distinct forms: mycelia (filamentous cells) and yeasts (spherical cells). While some dimorphic fungi produce commercially valuable products, others cause diseases in plants or mammals. These fungi must be able to sense and respond to various environmental cues, such as temperature, humidity, and carbon dioxide, to survive and thrive. Despite the importance of carbon dioxide, how dimorphic fungi sense and respond to this gas molecule remains largely unknown. The results from this project will fill this critical knowledge GAP and help develop novel antifungal drugs and agricultural fungicides to combat life-threatening fungal infections and reduce crop damage, respectively. This project will be carried out at rhodes college and undergraduate students enrolled at rhodes and students attending lemoyne-owen college, a local historically black college, will participate in this project. To expand undergraduate research opportunities, this project will support a course-based research experience for students enrolled in the microbiology course at rhodes. This project will investigate the molecular mechanisms by which dimorphic fungi sense and respond to carbon dioxide using the model dimorphic fungal organism, histoplasma capsulatum. Preliminary studies conducted by the principal investigator demonstrate that elevated carbon dioxide enhances amino acid metabolism and reduces antifungal susceptibility in histoplasma. This project will genetically and biochemically characterize histoplasma?s putative carbonic anhydrases which facilitate rapid inter conversion of carbon dioxide and water into carbonic acid, protons, and bicarbonate ions. Two independent approaches (genetic screen and DNA pull-down assay) will be used to identify genes that regulate the expression of putative carbonic anhydrase encoding genes in histoplasma. RNA-SEQ based transcriptional profiling will be performed to identify genes that are upregulated under elevated carbon dioxide and determine whether overexpression of these genes in histoplasma will result in enhanced amino acid metabolism and/or reduced antifungal susceptibility regardless of environmental carbon dioxide concentrations. This project will uncover novel cellular components involved in carbon dioxide sensing in histoplasma and advance the current understanding of how fungi sense and respond to environmental cues. This project is jointly funded by the divisions of molecular and cellular biosciences and biological infrastructure of the biological sciences directorate. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the foundation's intellectual merit and broader impacts review criteria.- subawards are not planned for this award.