2013 Annual Report
1a.Objectives (from AD-416):
Plants possess sensors for detecting phytopathegenic microbes and triggering defense responses; bacteria deploy effector proteins to defeat these plant defense systems. Recent and emerging work, including that done by the collaborator, is providing insight into the specific relationships between bacterial effectors and plant defense pathways. This agreement proposes to leverage this information to build network models of plant-microbe interactions. These models can be used for better understanding pathogenesis, the relationship between effector suites and host range, and the co-evolutionary process that gave rise to the effector suites and plant defense pathways that are observed in nature.
1b.Approach (from AD-416):
This study will focus initially on understanding the specific interactions between Pseudomonas syringae pv. tomato DC3000 and tomato (Solanum lycopersicum), particularly those involving pathogen effector proteins and plant immunity-associated kinases. A wide variety of methodologies will be used to dissect the plant-microbe interaction, and new strategies will be developed as required. On the microbial side, the range of possible techniques include the generation, selection and screening of mutants under various conditions, the creation of targeted mutants using molecular methods, and the construction of strains that over-express genes of interest. On the plant side, virus-induced gene silencing (VIGS), protein microarrays, and yeast two-hybrid assays will be used to determine which kinases are involved in the immune response and which microbial proteins target these kinases to compromise immunity. Computational methods will be used to determine effector suites in sequenced strains of P. syringae and to develop network models of the interaction between these suites, the tomato kinases and other plant genes targeted by bacterial effectors.
During this reporting period, an undergraduate student was hired and assigned tasks related to the parent project's research, including characterizing small RNA (sRNA) mutants. In particular, work funded by the parent project suggested that in the bacteria, Pseudomonas syringae pv. tomato DC3000, a particular sRNA, Spot 42, was involved in causing plant disease. The undergraduate helped developed a Spot 42 mutant of DC3000 and studied its response to a number of growth conditions. The experiments suggest that Spot 42 plays a role in protecting the bacterium while inside the plant. This and other findings will help us better understand how bacteria cause disease in plants and lead to the development of more effective control strategies.