CBB Seminar: The whole genome sequence of Pseudomonas syringae pv. actinidiae: insights into genome dynamics, pathogenicity and strategies for resistance Event as iCalendar

(Seminars)

04 April 2013

18 - 18pm

Venue: Tāmaki Campus, University of Auckland, Building 733 Rm 201

Host: Centre for Biodiversity and Biosecurity

image kiwifruit talk

Matt Templeton
Principal Scientist, Plant & Food Research


Most crops were domesticated centuries - even millennia - ago, thus limiting opportunity to understand the emergence of disease. Kiwifruit is an exception: domestication began in the 1930s with outbreaks of canker disease caused by P. syringae pv. actinidiae (Psa) first recorded in the 1980s. Based on SNP analyses of two circularized and 30 draft genomes, Psa comprises distinct clades exhibiting negligible within-clade diversity, consistent with disease arising by independent samplings from a source population. Three clades correspond to their geographical source of isolation; a fourth, encompassing the Psa-V lineage responsible for the 2008 outbreak, is now globally distributed. Psa has an overall clonal population structure, however, genomes carry a marked signature of within-pathovar recombination. Most SNP polymorphisms reside within PPHGI-1-like conjugative elements whose evolution is unlinked to the core genome. Removal of SNPs due to recombination yields an uninformative (star-like) phylogeny consistent with diversification of Psa-V from a single clone within the last ten years. Growth assays provide evidence of cultivar specificity, with rapid systemic movement of Psa-V in Actinidia chinensis. Genomic comparisons show a dynamic genome with evidence of positive selection on type III effectors and other candidate virulence genes. Each clade has highly varied complements of accessory genes encoding effectors and toxins with evidence of gain and loss via multiple genetic routes. Genes with homologs in vascular pathogens were found exclusively within Psa-V. Our analyses capture a pathogen in the early stages of emergence from a predicted source population associated with wild Actinidia species.

 

Catching the staff shuttle to the Tamaki Campus

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