Jennifer Lewis is the new Principal Investigator at the Plant Gene Expression Center in Albany, a partner institution with the Department of Plant & Microbiology.
Lewis started in November, 2011 and her official appointment as an adjunct assistant professor will be July 1, 2012. She carried out her Ph.D. research with Dr. Sondra Lazarowitz at Cornell and her postdoctoral research with Drs. Darrell Desveaux and David Guttman at the University of Toronto.
The Lewis Lab is interested in identifying novel defense signaling components in plants which respond to bacterial pathogens, and applying this knowledge to crop species to prevent disease.
While at the Lazarowitz lab Lewis studied gemini viruses. While Lewis was looking for proteins that interacted with the movement protein from Cabbage Leaf Curl Virus, she surprisingly found SYTA, a synaptotagmin. Synaptotagmin had previously been found only in animals, where it has a role in neurotransmitter release. Lewis showed that SYTA also interacts with movement proteins from the closely related Squash Leaf Curl Virus and unrelated viruses, such as Tobacco Mosaic Virus (TMV). Furthermore, viral infection was delayed in a syta mutant, and cell-to-cell spread of movement proteins was inhibited. Her work therefore provided evidence for an endocytic recycling pathway in plant cells that traffics movement proteins to plasmodesmata.
For her postdoctoral research, Lewis characterized the evolutionary diverse HopZ family of type III effector proteins from Pseudomonas syringae. Plants infected with P. syringae expressing hopZ2 had enhanced bacterial growth but those infected with P. syringae expressing hopZ1a had reduced bacterial growth and a hypersensitive response (HR). To identify plant proteins that were necessary for the recognition of hopZ1a, she infected mutants in known Arabidopsis resistance genes and signaling components. However, all of the tested mutants still showed an HR response against P syringae carrying hopZ1a, indicating that the recognition of HopZ1a was novel. She then created and screened a resource of knockouts in R genes to identify the R gene that responds to HopZ1a, which she named ZAR1, for HopZ Activated Resistance. Bacterial growth in zar1 mutants was significantly increased. These results suggest that HopZ1a promotes virulence when zar1 is non-functional. Screens for additional mutants yielded ZED1 and ZED2. ZED1 encodes a kinase that is necessary for the recognition of HopZ1a.
In her lab at the PGEC she will continue to dissect the signaling pathway by which HopZ1a is recognized in Arabidopsis, and initiate studies of homologous pathways in crop species. Lewis welcomes interest from graduate students and undergraduates who are excited to pursue research on novel innate immunity signaling pathways in plants.
The Lewis lab studies plant immune responses to Pseudomonas syringae, a bacterial pathogen that can infect a broad range of plant species, from important crop plants to the model plant Arabidopsis thaliana. P. syringae employs a specialized syringe-like structure called the type III secretion system to inject virulence proteins termed "effectors" directly into the cells of its plant host. In response, plants have evolved a surveillance system to recognize the presence of type III secreted effector (T3SE) as a trigger for immunity. The sentinels of this surveillance system are termed resistance (R) proteins. HopZ1a is part of the important YopJ superfamily of T3SEs whose archetypical member, YopJ, is found in the causal agent of the bubonic plague, Yersinia pestis. Recognition of HopZ1a by the ZAR1 resistance protein in Arabidopsis leads to the initiation of immune responses. ZAR1-mediated immunity is independent of known resistance-related genes suggesting that ZAR1 possesses novel signaling requirements.
The Lewis lab is interested in identifying these novel defense signaling components and applying this knowledge to crop species to prevent disease.
Jennifer D. Lewis will give a special seminar on Friday, Feb. 10, 2012 from noon to 1 pm on the UC Berkeley campus. The seminar is entitled "Arabidopsis Innate Immunity and the HopZ Family of Effector Proteins". Please watch our website for an update on the location.