Evolution of plant pathogenesis in Pseudomonas syringae: a genomics perspective.

The phytopathogenic bacterium Pseudomonas syringae causes serious diseases in a wide range of important crop plants, with recent severe outbreaks on the New Zealand kiwifruit crop and among British horse chestnut trees. Next-generation genome sequencing of over 25 new strains has greatly broadened our understanding of how this species adapts to a diverse range of plant hosts. Not unexpectedly, the genomes were found to be highly dynamic, and extensive polymorphism was found in the distribution of type III secreted effectors (T3SEs) and other virulence-associated genes, even among strains within the same pathovar. An underexplored area brought to light by these data is the specific metabolic adaptations required for growth on woody hosts. These studies provide a tremendous wealth of candidates for more refined functional characterization, which is greatly enhancing our ability to disentangle the web of host-pathogen interactions that determine disease outcomes.