Lewis Lab Research

We are interested in understanding the molecular mechanisms of plant immunity, and how pathogens adapt to host recognition. Our research focuses on Pseudomonas syringae, a Gram-negative bacterial pathogen that can infect more than 100 plant species. P. syringae uses the type III secretion system to secrete and translocate effector proteins into the plant. Many of these effector proteins are believed to function primarily in the suppression of host defense signaling. However recognition of these effector proteins by resistance (R, also called NLR) proteins induces immunity.

Immunity and Crop Species

Tomato leaves infected with Pseudomonas syringae (top) or uninfected (bottom)
Pathogens cause significant crop losses in the absence of durable resistance. This can be exacerbated by climate change as pathogens move into new territories. We are interested in using natural genetic diversity to identify genes that can protect plants from pathogens.

Undergraduate Research Opportunities

Undergraduate Tania Funes working with plants
We are looking for highly motivated undergraduate students who are interested in and are enthusiastic about conducting scientific research.

ZAR1 Immune Receptor

HopZ1a is recognized in Col-0 wild type plants, causing a defense response while zar1 mutants lose the defense response
Pathogen effector proteins can be recognized by nucleotide-binding-site leucine-rich repeat receptors (NLRs), resulting in rapid defense responses. We developed ARTIC, the Arabidopsis Resistance gene T-DNA Insertion Collection, as a robust reverse genetic approach to identify NLRs that recognize specific effector proteins. We discovered that the Pseudomonas syringae type III effector protein HopZ1a is recognized by ZAR1. ZAR1 appears to be an ancient Resistance gene that is found in many plant species.

Immune Signaling Pathways

Host immune signaling is induced after recognition of a bacterial effector protein
Host resistance typically involves signaling proteins like NDR1 or EDS1, salicylic acid and reactive oxygen species. HopZ1a is recognized by ZAR1, a coiled-coil nucleotide binding-site leucine-rich-repeat immune receptor in plants. However HopZ1a-induced resistance does not require any of the typical immune signaling proteins. Using a forward genetic approach, we have identified mutants that lack a HopZ1a-mediated defense response and are characterizing their roles in immunity.