Purine catabolites as inducers of bacterial gene expression

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When a bacterial pathogen infects a host, the host mounts a defense, which is intended to kill the invader. The bacteria, however, counter such defenses, often harnessing the very host-derived defense compounds to trigger changes in their own metabolism, changes that are designed to promote their survival in the inhospitable host environment. This project aims to delineate mechanisms by which bacterial plant pathogens detect and exploit host-derived signals to promote survival and virulence. A more complete understanding of the infection process will lead to novel insights into the lifecycle of economically important plant pathogens and ultimately inspire efforts to control disease progression. This program also offers an opportunity for advancing discovery while creating an inclusive training environment for students. Graduate students will be integral to developing this research project, and they will be encouraged to pursue career-building opportunities. For undergraduate students, many of whom will be recruited from institutionally established programs for minority students, a substantive research experience not only integrates with their required coursework, but it also enhances their value when entering the job market or seeking admission to professional schools. Overall, these training opportunities contribute to the development of a competitive STEM workforce.Part of the host response to pathogens is the production of reactive oxygen species. The purine catabolites urate and xanthine accumulate during infection because one of the host enzymes responsible for production of reactive oxygen species is xanthine oxidoreductase, which otherwise participates in purine metabolism by converting hypoxanthine to xanthine and xanthine to urate. Previous work has shown that PecS family transcription factors bind these purine catabolites. The primary objective of this project is to address the hypothesis that other urate/xanthine-responsive transcription factors exist. Using Burkholderia thailandensis, which encodes the PecS-family protein MftR, a combination of immunoprecipitation and mass spectrometry will be implemented to identify additional purine-responsive transcription factors. Identified proteins will be analyzed in vitro in terms of DNA and ligand binding, and in vivo experiments will include analyses of gene expression and phenotypes characteristic of strains deleted for genes encoding the identified transcription factor as well as chromatin immunoprecipitation to identify direct targets. The ability of MftR to rewire these regulatory circuits will be examined. By focusing on several proteins that respond to the same signals, the objective is to achieve a more integrated picture of the gene regulatory networks affected by purine catabolites.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.