The investigators will examine the role of extracellular DNA (exDNA) in plant defense and extracellular DNase (exDNase) as a virulence factor in plant pathogens. A series of recent studies describe a novel role for exDNA in mammalian defense against microbial pathogens by trapping and killing the invading microbes. Mutation of microbial exDNases that enable microorganisms to degrade exDNA results in loss of virulence, thus demonstrating that these exDNases are virulence factors. During the same period, emerging data from the Hawes lab suggest that exDNA also is required for defense against microbial invasion of the plant root tip. When plant exDNA is degraded by exogenous DNase, as in animal systems, resistance against pathogenic invasion is abolished. The goal of this project is to examine the hypothesis that exDNA is a previously unrecognized component of plant innate immunity. The primary experimental approach is to measure the impact of exDNase gene mutation on virulence among bacterial and fungal pathogens. These experiments are designed to establish a framework for defining conditions under which exDNA functions in plant defense, how commonly it plays a key role among diverse pathogen-host interactions, and at what level(s) of innate immunity this process operates. This project addresses basic questions of how microbial infection affects plant growth, development, and productivity. As such, the work impacts current methods for the control of agricultural pests and aids in the design of new strategies to prevent plant diseases. The plant model for exDNA function will also complement ongoing work in exDNA-based medical immune responses. The proposed research will lend itself to projects that allow undergraduates from the University of Arizona and from Oberlin, Macalester, Luther and other participating colleges in the UA's Winter Internship Program to experience independent laboratory research.
