CAREER: Dissecting the cellular pathways and signaling networks orchestrating plant defense responses and their interplay with bacterial virulence factors

Plant diseases caused by microorganisms have a significant impact on agricultural productivity and, consequently affect the availability of food and fiber for an ever-growing human population. To fight potential pathogens, plants have evolved a complex defense system that detects the presence of potential pathogens and activates multiple responses to restrict pathogen proliferation and prevent tissue damage. Some of these responses include the fortification of the cell wall and the release of molecules with antimicrobial properties. In spite of these and other defense responses diseases still occur because pathogens have also evolved multiple strategies to avoid the plant defense system. The objective of this project is to understand how plants fortify the cell wall and release antimicrobials, and how pathogens interfere with these processes. This knowledge will shed light into new approaches to control plant diseases and reduce their economic and societal impact. The research activities from this project will be used to engage undergraduate students from under-represented minorities, and will provide multi-disciplinary training for postdoctoral fellows and graduate students, who will also be mentors in the outreach activities. <br/><br/>The plant endomembrane system is essential for pathogen recognition, and for the deployment of defense responses such as the remodeling of the cell wall and the delivery of proteins with antimicrobial properties to the extracellular milieu (apoplast). Both of these responses require protein secretion, a process that has been investigated but remains poorly understood, especially in plants, as it involves multiple and highly dynamic subcellular compartments, trafficking pathways and protein networks. Because endomembrane-mediated processes are essential in plant-pathogen interactions, these processes are also targets of pathogen's virulence factors, but the strategies that pathogens use have not been well characterized. The main objective of this project is to gain a deeper understanding into secretory pathways and signaling networks regulating plant defense responses and how these processes are targeted by virulence factors from bacterial pathogens. This project will use multi-disciplinary approaches involving live-cell imaging and proteomics technologies in combination with biological, genetic and biochemical assays to identify subcellular compartments, trafficking pathways and protein networks operating in cell wall remodeling and delivery of antimicrobial proteins to the apoplast. The project will also provide a framework to compare how bacterial pathogens with contrasting lifestyles trigger distinct sets of molecular and cellular responses, and how synergistic interactions between virulence factors from adapted bacterial pathogens subvert plant immune responses. This project is jointly funded by the Plant Biotic Interactions Program and the Established Program to Stimulate Competitive Research (EPSCoR).<br/><br/>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.