Research
My broad interest is in how organisms adapt to a changing environment. My lab studies this in the context of pathogen-host interactions using the gram negative pathogen Pseudomonas syringae and its interaction with several plants: the non-crop models Arabidopsis thaliana and Nicotiana benthamiana, and the crop plants tomato and snap beans. In response to infection, plants mount a complex local defense response involving cell suicide, changes at the plasma membrane, the crosslinking of cell wall components, production of antimicrobials and defense gene activation. Some leaf infections induce a primed state that allows plants to respond faster when a second infection occurs on distal leaves (systemic acquired resistance, SAR). Interactions of roots with beneficial microbes also induces a primed state in the aerial part of the plant (and induced systemic resistance, ISR). Although SAR and ISR were considered different immune programs, we have found that some of the same are proteins required for both systemic programs. These proteins are involved in mobilizing small molecule signals. The lab investigates plant defense and pathogen virulence mechanisms.

We study how plants regulate their responses to pathogens by (1) using plant mutants that express one or more aspects of the defense response in the absence of pathogens or are compromised for local defense activation or SAR, (2) discovering and tracking the production and movement of novel defense signals and pathogen-derived molecules, and (3) exploiting secreted virulence effector proteins from the pathogen to discover immune components and discern how they are modified. This involves combining genetic analysis (including mosaic plants in which only some cells/tissues express specific defense components) with biochemistry and cell biology. We are very interested in how the defense response is coordinated and towards this end, we are investigating the sites of action at the tissue and subcellular levels of key SAR/ISR proteins. On the pathogen side, we are also characterizing how P. syringae uses its type III secretion apparatus and secreted effectors to modulate immunity and colonize plant tissue, including the surfaces of a leaf, a unique niche. We are using proteomic approaches to discern how pathogen effectors post-translationally modify both other pathogen effectors and host immune complexes to suppress signaling. We are interested in exploiting what we learn about P. syringae effectors to study orthologous effectors from diverse pathogens of both plants and animals.

A recent additional interest is in peptide trafficking and signal output as it relates to development and microbial interactions.

Our lab welcomes participants from all over the world and at many levels of education (high school, college, predoctoral, postdoctoral and teachers).

Professional Activities and Service
I have been a Senior Editor of The Plant Cell, a Reviewing Editor of eLIFE and Secretary to the Board of Directors of the International Society of Plant-Microbe Interactions.

I am a member of the American Society of Plant Biology and the Society for Experimental Biology. I participated in developing and writing a recently published white paper concerning the promotion of plant heath: "Foundational and translational research opportunities to improve plant health." Currently I am a member of the Plant Biology Advisory Board for Landmarks.

I am a strong advocate for diversity in science and serve on the University of Chicago Division of Biology's Diversity Committee and on the steering committee of the Molecular Genetics and Cell Biology Department's National Science Foundation-sponsored Research Education for Undergraduates program.