PhD Transfer Exam – Bradley Laflamme (Desveaux/Guttman labs)

PhD Transfer Exam

Tuesday May 23^rd, 1:10 pm – Earth Sciences Centre, Rm. 3087

Bradley Laflamme (Desveaux/Guttman labs)

“Identifying new building blocks of type III effector-mediated virulence using the Arabidopsis-Pseudomonas syringae pathosystem”

Abstract

Pseudomonas syringae is a Gram-negative bacterial pathogen which infects many plant species, including the model plant Arabidopsis. The virulence of this pathogen requires its type III secretion system, which is used to inject a collection of “effector” virulence proteins directly into host cells to evade immunity and improve pathogenesis. While each strain of P. syringae is virulent on only a small number of hosts, effectors isolated from phylogenetically diverse strains often still have virulence functions in non-hosts, reflective of the fact that they target conserved facets of immunity across plant species. However, the vast majority of diverse effector variants across all sequenced P. syringae isolates have no characterization in terms of how they contribute to virulence in any plant background. To address effector-mediated virulence as a broad phenomenon, our labs have begun developing a type III effector compendium (T3EC) which collects effector sequences from across diverse isolates as a resource for wet-lab experiments. Using several pathogenicity assays which characterize effector-mediated virulence in distinct ways, we plan to screen and annotate the T3EC for virulence activity in Arabidopsis. After identifying effectors which contribute to particular aspects of P. syringae virulence, we will then explore synergistic relationships between these effectors, with our final goal being to develop a novel pathogen of Arabidopsis with a profile of synergistic effectors not found in any naturally occurring strain. This project will elucidate how effectors involved in targeting distinct immune processes intersect and amplify one another to dismantle plant immunity in successful pathogens.