Comparative genomics of Pseudomonas syringae reveals convergent gene gain and loss associated with specialization onto cherry (Prunus avium)

Michelle T. Hulin, Andrew D. Armitage, Joana G. Vicente, Eric B. Holub, Laura Baxter, Helen J. Bates, John W. Mansfield, Robert W. Jackson, Richard J. Harrison*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)
149 Downloads (Pure)


Genome-wide analyses of the effector- and toxin-encoding genes were used to examinethe phylogenetics and evolution of pathogenicity amongst diverse strains of Pseudomonas syringae causing bacterial canker of cherry (Prunus avium), including pathovars P. syringae pv morsprunorum (Psm) races 1 and 2, P. syringae pv syringae (Pss) and P. syringae pv avii

Phylogenetic analyses revealed Psm races and P. syringae pv avii clades were distinct and were each monophyletic, whereas cherry-pathogenic strains of Pss were interspersed amongst strains from other host species. 

A maximum likelihood approach was used to predict effectors associated with pathogenicity on cherry. Pss possesses a smaller repertoire of type III effectors but has more toxin biosynthesis clusters than Psm and P. syringae pv avii. Evolution of cherry pathogenicity wascorrelated with gain of genes such as hopAR1 and hopBB1 through putative phage transferand horizontal transfer respectively. By contrast, loss of the avrPto/hopAB redundant effectorgroup was observed in cherry-pathogenic clades. Ectopic expression of hopAB and hopC1 triggered the hypersensitive reaction in cherry leaves, confirming computational predictions. 

Cherry canker provides a fascinating example of convergent evolution of pathogenicity thatis explained by the mix of effector and toxin repertoires acting on a common host.

Original languageEnglish
Pages (from-to)672-696
Number of pages25
JournalNew Phytologist
Issue number2
Early online date4 May 2018
Publication statusPublished - Jul 2018


  • avirulence
  • bacterial canker
  • comparative genomics
  • host specialization
  • prediction
  • Pseudomonas
  • toxins
  • type III effectors

ASJC Scopus subject areas

  • Physiology
  • Plant Science


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