Population-genomic insights into emergence, crop-adaptation, and dissemination of Pseudomonas syringae pathogens
Monteil, CL; Yahara, K; Studholme, DJ; et al.Mageiros, L; Méric, G; Swingle, B; Morris, CE; Vinatzer, BA; Sheppard, SK
Date: 20 September 2016
Journal
Microbial Genomics
Publisher
Microbiology Society
Publisher DOI
Abstract
Many bacterial pathogens are well characterized but, in some cases, relatively little is
known about the populations from which they emerged. This limits understanding of
the molecular mechanisms underlying disease. The crop pathogen Pseudomonas
syringae sensu lato has been widely isolated from the environment, including wild
plants ...
Many bacterial pathogens are well characterized but, in some cases, relatively little is
known about the populations from which they emerged. This limits understanding of
the molecular mechanisms underlying disease. The crop pathogen Pseudomonas
syringae sensu lato has been widely isolated from the environment, including wild
plants and components of the water cycle, and causes disease in several economically
important crops. Here, we compared genome sequences of 45 P. syringae crop
pathogen outbreak strains with 69 closely related environmental isolates. Phylogenetic
reconstruction revealed that crop pathogens emerged many times independently from
environmental populations. Unexpectedly, differences in gene content between
environmental populations and outbreak strains were minimal with most virulence
genes present in both. However, a genome-wide association study identified a small
number of genes, including the type III effector genes hopQ1 and hopD1, to be
associated with crop pathogens, but not with environmental populations, suggesting
that this small group of genes may play an important role in crop disease emergence.
Intriguingly, genome-wide analysis of homologous recombination revealed that the
locus Psyr 0346, predicted to encode a protein that confers antibiotic resistance, has
been frequently exchanged among lineages and thus may contribute to pathogen
fitness. Finally, we found that isolates from diseased crops and from components of the
water cycle, collected during the same crop disease epidemic, form a single
population. This provides the strongest evidence yet that precipitation and irrigation
water are an overlooked inoculum source for disease epidemics caused by P.
syringae.
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