title: Flagellin is not a major defense elicitor in Ralstonia solanacearum cells or extracts applied to Arabidopsis thaliana.
abstract: The phytopathogenic bacterium Ralstonia solanacearum requires motility for full virulence, and its flagellin is a candidate pathogen-associated molecular pattern that may elicit plant defenses. Boiled extracts from R. solanacearum contained a strong elicitor of defense-associated responses. However, R. solanacearum flagellin is not this elicitor, because extracts from wild-type bacteria and fliC or flhDC mutants defective in flagellin production all elicited similar plant responses. Equally important, live R. solanacearum caused similar disease on Arabidopsis ecotype Col-0, regardless of the presence of flagellin in the bacterium or the FLS2-mediated flagellin recognition system in the plant. Unlike the previously studied flg22 flagellin peptide, a peptide based on the corresponding conserved N-terminal segment of R. solanacearum, flagellin did not elicit any response from Arabidopsis seedlings. Thus recognition of flagellin plays no readily apparent role in this pathosystem. Flagellin also was not the primary elicitor of responses in tobacco. The primary eliciting activity in boiled R. solanacearum extracts applied to Arabidopsis was attributable to one or more proteins other than flagellin, including species purifying at approximately 5 to 10 kDa and also at larger molecular masses, possibly due to aggregation. Production of this eliciting activity did not require hrpB (positive regulator of type III secretion), pehR (positive regulator of polygalacturonase production and motility), gspM (general secretion pathway), or phcA (LysR-type global virulence regulator). Wild-type R. solanacearum was virulent on Arabidopsis despite the presence of this elicitor in pathogen extracts.
authors.affiliation: Department of Plant Pathology, University of Wisconsin, Madison, 1630 Linden Drive, Madison, WI 53706, USA.
authors.forename: Christine
authors.initials: C
authors.lastname: Pfund
authors.forename: Julie
authors.initials: J
authors.lastname: Tans-Kersten
authors.forename: F Mark
authors.initials: FM
authors.lastname: Dunning
authors.forename: Jose M
authors.initials: JM
authors.lastname: Alonso
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Ecker
authors.forename: Caitilyn
authors.initials: C
authors.lastname: Allen
authors.forename: Andrew F
authors.initials: AF
authors.lastname: Bent
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D002457:Cell Extracts / Q000494:pharmacology; D016384:Consensus Sequence; D005407:Flagella / Q000502:physiology; D005408:Flagellin / Q000737:chemistry; D008969:Molecular Sequence Data; D009068:Movement; D010455:Peptides / Q000737:chemistry / Q000494:pharmacology; D010935:Plant Diseases / Q000382:microbiology; D011494:Protein Kinases / Q000378:metabolism; D043368:Ralstonia solanacearum / Q000166:cytology / Q000472:pathogenicity* / Q000502:physiology; D036226:Seedlings / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D014026:Nicotiana / Q000187:drug effects / Q000382:microbiology; D037521:Virulence Factors / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D002457:Cell Extracts; D010455:Peptides; D037521:Virulence Factors; D005408:Flagellin; D011494:Protein Kinases; C411853:FLS2 protein, Arabidopsis