Comparative genomics of two Pseudomonas plant pathovars. Pseudomonas syringae

A comparison of an epiphytic strain (B728a) that colonizes plant surfaces before causing disease, and an endophytic strain (DC3000) that poorly colonizes plant surfaces but can grow inside the host. Genomic comparison revealed 9 major chromosome rearrangements between the two strains, but GC-skew analysis indicates that these rearrangements occurred a significant amount of time in evolutionary history. B782a has fewer IS elements than DC3000, but there are 14 genomic island in B782a as compared to DC3000 including a prophage similar to LambdaSO from Shewanella oneidensis and another similar to the conjugative plasmid pKLC102 of Pseudomonas aeruginoase PAO1. B728a carries an ice nucleation gene (Psyr_1608) which produces an outer membrane protein that forms an ice nucleation center and a separate gene (Psyr_0931) that produces an antifreeze protein. There are significant differences in the virulence genes and systems carried by these two organisms which probably have roles in host and tissue specificity.