title: The molecular basis of host specialization in bean pathovars of Pseudomonas syringae.
abstract: Biotrophic phytopathogens are typically limited to their adapted host range. In recent decades, investigations have teased apart the general molecular basis of intraspecific variation for innate immunity of plants, typically involving receptor proteins that enable perception of pathogen-associated molecular patterns or avirulence elicitors from the pathogen as triggers for defense induction. However, general consensus concerning evolutionary and molecular factors that alter host range across closely related phytopathogen isolates has been more elusive. Here, through genome comparisons and genetic manipulations, we investigate the underlying mechanisms that structure host range across closely related strains of Pseudomonas syringae isolated from different legume hosts. Although type III secretion-independent virulence factors are conserved across these three strains, we find that the presence of two genes encoding type III effectors (hopC1 and hopM1) and the absence of another (avrB2) potentially contribute to host range differences between pathovars glycinea and phaseolicola. These findings reinforce the idea that a complex genetic basis underlies host range evolution in plant pathogens. This complexity is present even in host-microbe interactions featuring relatively little divergence among both hosts and their adapted pathogens.
authors.affiliation: School of Plant Sciences, The University of Arizona, Tucson, AZ 85721-0036, USA. baltrus@email.arizona.edu
authors.forename: David A
authors.initials: DA
authors.lastname: Baltrus
authors.forename: Marc T
authors.initials: MT
authors.lastname: Nishimura
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Dougherty
authors.forename: Surojit
authors.initials: S
authors.lastname: Biswas
authors.forename: M Shahid
authors.initials: MS
authors.lastname: Mukhtar
authors.forename: Joana
authors.initials: J
authors.lastname: Vicente
authors.forename: Eric B
authors.initials: EB
authors.lastname: Holub
authors.forename: Jeffery L
authors.initials: JL
authors.lastname: Dangl
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D005075:Biological Evolution; D004269:DNA, Bacterial / Q000235:genetics; D007887:Fabaceae / Q000235:genetics / Q000382:microbiology*; D016680:Genome, Bacterial / Q000235:genetics*; D023281:Genomics; D058507:Host Specificity / Q000235:genetics; D054884:Host-Pathogen Interactions / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology; D010957:Plasmids / Q000235:genetics; D044224:Pseudomonas syringae / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D014774:Virulence / Q000235:genetics; D037521:Virulence Factors / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D037521:Virulence Factors