title: A tomatinase-like enzyme acts as a virulence factor in the wheat pathogen Fusarium graminearum.
abstract: During their interactions with plants, fungal pathogens employ large numbers of pathogenesis-associated molecules including secreted effectors and enzymes that can degrade various defence compounds. However, in many cases, in planta targets of pathogen-produced enzymes remain unknown. We identified a gene in the wheat pathogen Fusarium graminearum, encoding a putative enzyme that shows 84% sequence identity to FoTom1, a tomatinase produced by the tomato pathogen Fusarium oxysporum f. sp. lycopersici. In F. oxysporum f. sp. lycopersici, FoTom1 is a virulence factor involved in the degradation of tomato defence compound tomatine, a saponin compound. Given that wheat is unknown to produce tomatine, we tested the ability of F. graminearum to degrade tomatine and found that F. graminearum was unable to degrade tomatine in culture. However, FgTom1 degraded tomatine in vitro when heterologously expressed. To determine the possible function of FgTom1 in pathogen virulence, we generated FgTom1 knockout mutants (ΔTom1). ΔTom1 mutants were not different from wild type when grown in culture but showed significant reduction in pathogen virulence in root rot and head blight assays. In an attempt to identify possible in planta targets of FgTom1, the metabolomes of wheat heads infected with wildtype pathogen and ΔTom1 were compared and several peaks differentially abundant between treatments identified. Although the exact identity of these peaks is currently unknown, this result suggested that FgTom1 may have in planta targets in wheat, possibly tomatine-like saponin compounds. Overall, our results presented here show that FgTom1 is a new virulence factor in F. graminearum.
authors.affiliation: Commonwealth Scientific and Industrial Research Organization (CSIRO) Agriculture and Food, Queensland Bioscience Precinct, Brisbane, Queensland 4067, Australia. Electronic address: Jason.Carere@Canada.ca.
authors.forename: Jason
authors.initials: J
authors.lastname: Carere
authors.affiliation: Commonwealth Scientific and Industrial Research Organization (CSIRO) Agriculture and Food, Queensland Bioscience Precinct, Brisbane, Queensland 4067, Australia.
authors.forename: Aurélie H
authors.initials: AH
authors.lastname: Benfield
authors.affiliation: Commonwealth Scientific and Industrial Research Organization (CSIRO) Agriculture and Food, Queensland Bioscience Precinct, Brisbane, Queensland 4067, Australia.
authors.forename: Mélodie
authors.initials: M
authors.lastname: Ollivier
authors.affiliation: Commonwealth Scientific and Industrial Research Organization (CSIRO) Agriculture and Food, Queensland Bioscience Precinct, Brisbane, Queensland 4067, Australia.
authors.forename: Chunji J
authors.initials: CJ
authors.lastname: Liu
authors.affiliation: Commonwealth Scientific and Industrial Research Organization (CSIRO) Agriculture and Food, Queensland Bioscience Precinct, Brisbane, Queensland 4067, Australia.
authors.forename: Kemal
authors.initials: K
authors.lastname: Kazan
authors.affiliation: Commonwealth Scientific and Industrial Research Organization (CSIRO) Agriculture and Food, Queensland Bioscience Precinct, Brisbane, Queensland 4067, Australia.
authors.forename: Donald M
authors.initials: DM
authors.lastname: Gardiner
mesh_terms: D060467:Disease Resistance / Q000235:genetics*; D005670:Fusarium / Q000201:enzymology* / Q000472:pathogenicity; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism*; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D018517:Plant Roots / Q000378:metabolism / Q000382:microbiology; D014053:Tomatine / Q000737:chemistry / Q000378:metabolism; D014908:Triticum / Q000382:microbiology*; D037521:Virulence Factors / Q000737:chemistry / Q000378:metabolism
chemical_list: D037521:Virulence Factors; D014053:Tomatine; D006026:Glycoside Hydrolases; C099475:tomatinase
keywords: Defense compounds; Fusarium; Phytoanticipin; Saponin; Secondary metabolites; Tomatine