title: A role for a flavin-containing mono-oxygenase in resistance against microbial pathogens in Arabidopsis.
abstract: Using activation tagging in the Arabidopsis Col-0 rps2-101C background, we identified a mutant (FMO1-3D) that showed virtually no symptoms after inoculation with virulent Pseudomonas syringae pv. tomato DC3000 bacteria. The dominant, gain-of-function phenotype of the FMO1-3D mutant is due to over-expression of a class 3 flavin-containing mono-oxygenase (FMO). We recapitulated the FMO1-3D mutant phenotype in independent transgenic Col-0 lines over-expressing the FMO1 cDNA under the control of the 35S CaMV promoter. The increased basal resistance observed in the FMO1-3D mutant was also effective against the taxonomically unrelated downy mildew-causing pathogen Hyaloperonospora parasitica. By investigating the progeny from crosses of the FMO1-3D mutant with the NahG transgenic line, we showed that the enhanced basal resistance phenotype was dependent on the accumulation of salicylic acid. FMO1-3D plants showed wild-type resistant reactions after inoculation with avirulent bacteria, indicating that the R-gene-mediated defence physiology was not compromised by FMO1 over-expression. Transcripts of the class 3 FMO1 gene accumulated within 6 h after inoculation of wild-type Col-0 plants with avirulent Pst + avrRpt2 cells. Moreover, a T-DNA insertion into the FMO1 gene resulted in enhanced susceptibility to virulent Pseudomonas and Hyaloperonospora parasitica, suggesting that expression of the FMO1 gene is a hitherto undescribed component of the plant's resistance repertoire. We discuss the possibility that the FMO may participate in the detoxification of virulence factors produced by pathogens.
authors.affiliation: RWTH Aachen University, Institut Bio III Pflanzenphysiologie, 52056 Aachen, Germany.
authors.forename: Martina
authors.initials: M
authors.lastname: Koch
authors.forename: Sonja
authors.initials: S
authors.lastname: Vorwerk
authors.forename: Clarissa
authors.initials: C
authors.lastname: Masur
authors.forename: Gholamreza
authors.initials: G
authors.lastname: Sharifi-Sirchi
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Olivieri
authors.forename: Nikolaus L
authors.initials: NL
authors.lastname: Schlaich
mesh_terms: D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010105:Oxygenases / Q000737:chemistry / Q000378:metabolism*; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000378:metabolism / Q000382:microbiology; D030821:Plants, Genetically Modified
chemical_list: D029681:Arabidopsis Proteins; D010105:Oxygenases; C020066:dimethylaniline monooxygenase (N-oxide forming)