title: Specific surface glycan decorations enable antimicrobial peptide resistance in plant-beneficial pseudomonads with insect-pathogenic properties.
abstract: Some plant-beneficial pseudomonads can invade and kill pest insects in addition to their ability to protect plants from phytopathogens. We explored the genetic basis of O-polysaccharide (O-PS, O-antigen) biosynthesis in the representative insecticidal strains Pseudomonas protegens CHA0 and Pseudomonas chlororaphis PCL1391 and investigated its role in insect pathogenicity. Both strains produce two distinct forms of O-PS, but differ in the organization of their O-PS biosynthesis clusters. Biosynthesis of the dominant O-PS in both strains depends on a gene cluster similar to the O-specific antigen (OSA) cluster of Pseudomonas aeruginosa. In CHA0 and other P. protegens strains, the OSA cluster is extensively reduced and new clusters were acquired, resulting in high diversity of O-PS structures, possibly reflecting adaptation to different hosts. CHA0 mutants lacking the short OSA form of O-PS were significantly impaired in insect virulence in Galleria injection and Plutella feeding assays. CHA0, PCL1391, and other insecticidal pseudomonads exhibited high resistance to antimicrobial peptides, including cecropins that are central to insect immune defense. Resistance of both model strains depended on the dominant OSA-type O-PS. Our results suggest that O-antigen is essential for successful insect infection and illustrate, for the first time, its importance in resistance of Pseudomonas to antimicrobial peptides.
authors.affiliation: Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Kupferschmied
authors.affiliation: Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland.
authors.forename: Tiancong
authors.initials: T
authors.lastname: Chai
authors.affiliation: Plant Pathology, Institute of Integrative Biology, Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland.
authors.forename: Pascale
authors.initials: P
authors.lastname: Flury
authors.affiliation: Bioinformatics and Systems Biology, Justus-Liebig-University, Giessen, Germany.
authors.forename: Jochen
authors.initials: J
authors.lastname: Blom
authors.affiliation: Environmental Genomics and Systems Biology Research Group, Institute for Natural Resource Sciences, Zürich University of Applied Sciences, Wädenswil, Switzerland.
authors.forename: Theo H M
authors.initials: TH
authors.lastname: Smits
authors.affiliation: Plant Pathology, Institute of Integrative Biology, Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland.
authors.forename: Monika
authors.initials: M
authors.lastname: Maurhofer
authors.affiliation: Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland.
authors.forename: Christoph
authors.initials: C
authors.lastname: Keel
mesh_terms: D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D005247:Feeding Behavior; D009036:Moths / Q000382:microbiology* / Q000502:physiology; D019081:O Antigens / Q000096:biosynthesis*; D010935:Plant Diseases / Q000469:parasitology*; D010944:Plants / Q000382:microbiology / Q000469:parasitology; D011549:Pseudomonas / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity; D014774:Virulence
chemical_list: D023181:Antimicrobial Cationic Peptides; D001426:Bacterial Proteins; D019081:O Antigens