Effector gene persistence in bacterial plant pathogens

<p>This project will focus on understanding the mechanisms of effector gene persistence in the plant pathogenic bacterium Pseudomonas syringae pv. phaseolicola when it is exposed to a resistant bean host plant. We hypothesise that there may be an advantage to the bacteria maintaining the effector gene even in the resistant host and this effector gene persistence phenomenon is a wider spread mechanism for maintaining genetic diversity within bacterial populations. We thus aim to understand the mechanistic basis of effector persistence, the role it plays in plant pathogen interactions and if the phenomenon is wider than the model system we have used so far. This will be achieved through the following objectives: 1. Identify the genetic factors affecting PPHGI-1 persistence in resistant hosts 2. Identify the benefit to Pph of PPHGI-1 persistance in resistant hosts 3. Evaluate how pathogen transmission mechanisms affect effector persistence 4. To investigate the persistence of other P. syringae effectors 5. Using mathematical modelling in combination with experimental evolution to understand the dynamics of pathogen evolution to polygenic resistance The main methods to be used are: 1. Microbiological methods for culturing bacteria, analysing growth curves, examining competition 2. Plant inoculations to study the evolution of virulence: infiltrations, sprays, seed soaks, examining symptoms and removing bacteria from inoculated sites 3. Molecular biology techniques to clone genes, delete genes, carry out site-directed mutagenesis, examine island excision and integration (e.g. by Q-PCR) 4. Plant physiology and chemical analysis using Raman spectroscopy, GC-MS, AAS to examine apoplastic changes such as ROS production, callose deposition, ion and nutrient composition 5. Mathematical modelling to predict the outcomes of different effectors in different genomic contexts</p>