George Walters-Marrah, '19
I am a junior at UCF majoring in biotechnology and biomedical sciences with an emphasis on molecular microbiology. I find microbial pathogens and how they interact with the environment extraordinarily interesting. I currently study mycobacteria in Dr.Kyle Rohde's research lab at the UCF Burnett School of Biomedical Sciences. My career aspirations are to obtain a Ph.D. relating to immunity and pathogenesis, go into either academia or the biotechnology industry, and possibly start a biotech business based on a conceptual computer program that I am brainstorming about.
Dr. Kyle Rohde
Ph.D. in Immunology
Project title: Investigating the significance of acetylation by HopZ3 in Pseudomonas syringae
Conducted at the University of Chicago as part of the Molecular Genetics and Cell Biology REU
Dr. Jean Greenberg, Ph.D., Department of Molecular Genetics and Cell Biology, University of Chicago
Project Abstract: Pseudomonas syringae (Psy) is a bacterial plant pathogen and the causative agent of leaf spot. Psy’s success is largely due to its type III secretion system (T3SS) that enables it to inject a large repertoire of effector proteins into plant cells. The effector protein HopZ3 has been shown to suppress immune responses and promote bacterial growth. HopZ3 can bind to and acetylate the effector protein AvrPto and the tomato protein Pto, a member of the Prf immune complex found in tomato. Pto recognizes and interacts with AvrPto to activate the immune response during infection, but HopZ3-mediated acetylation reduces AvrPto-Pto interactions. This suggests that the acetylation sites found on AvrPto play a part in AvrPto-Pto interactions. This study focuses on the significance of two histidine acetylation sites found on AvrPto and their roles in detection and binding by Pto to activate the plant immune response. In vitro pull-down assays were used to test the importance of HopZ3- mediated histidine acetylation sites in AvrPto-Pto interactions. It was expected that a mutation of the histidine residues to alanine will have a similar effect as acetylation by HopZ3. Additionally, it is suspected that acetylation by HopZ3 can occur before secretion. This would give Psy a notable advantage because HopZ3 would be able to acetylate AvrPto before Pto is in the vicinity to perform a binding reaction. Therefore, AvrPto proteins, isolated from Psy induced by infection conditions, will be analyzed using mass spectrometry (MS) for signs of acetylation before secretion in vivo. These experiments gave insight into the specific mechanisms used by HopZ3 to suppress plant immune responses. It was found that mutation of the histidine acetylation sites on AvrPto does not compromise AvrPto-Pto interactions. And, AvrPto was expressed successfully in Psy and the protein was collected in T3SS-inducing conditions. AvrPto bands were cut and sent for MS analysis to detect possible acetylated residues.
Summer Research Institution
University of Chicago (NSF REU)
Medicine and Health Sciences
Walters-Marrah, George, "George Walters-Marrah, '19" (2017). McNair Scholars. 103.