Complete sequence of E rwinia piriflorinigrans plasmids p EPIR 37 and p EPIR 5 and role of p EPIR 37 in pathogen virulence

Erwinia piriflorinigrans is a newly described pathogen causing necrosis of pear blossoms. Complete sequencing of the 37‐kb plasmid pEPIR 37 common to 27 E . piriflorinigrans strains revealed homology to sequences of the ubiquitous plasmids p EA 29 of the fire blight pathogen E . amylovora , plasmid p EP 36 of E . pyrifoliae , plasmid p EJ 30 of E rwinia sp. from J apan, and genomic regions of the related R osaceae epiphytic E rwinia species E . tasmaniensis and E . billingiae . A second 5·5‐kb cryptic plasmid p EPIR 5, found in 12 E . piriflorinigrans strains, was also sequenced revealing mobilization and replication proteins with similarities to many small C ol E 1‐type plasmids in E rwinia spp. and other enterobacteria. Functional analyses of p EPIR 37 introduced into a strain of E . amylovora cured of p EA 29 plasmid, which has a reduced virulence, showed a role in increasing symptom development similar to that observed in E . amylovora carrying plasmid p EA 29.