title: A γ-lactamase from cereal infecting Fusarium spp. catalyses the first step in the degradation of the benzoxazolinone class of phytoalexins.
abstract: The benzoxazolinone class of phytoalexins are released by wheat, maize, rye and other agriculturally important species in the Poaceae family upon pathogen attack. Benzoxazolinones show antimicrobial effects on plant pathogens, but certain fungi have evolved mechanisms to actively detoxify these compounds which may contribute to the virulence of the pathogens. In many Fusarium spp. a cluster of genes is thought to be involved in the detoxification of benzoxazolinones. However, only one enzyme encoded in the cluster has been unequivocally assigned a role in this process. The first step in the detoxification of benzoxazolinones in Fusarium spp. involves the hydrolysis of a cyclic ester bond. This reaction is encoded by the FDB1 locus in F. verticillioides but the underlying gene is yet to be cloned. We previously proposed that FDB1 encodes a γ-lactamase, and here direct evidence for this is presented. Expression analyses in the important wheat pathogen F. pseudograminearum demonstrated that amongst the three predicted γ-lactamase genes only the one designated as FDB1, part of the proposed benzoxazolinone cluster in F. pseudograminearum, was strongly responsive to exogenous benzoxazolinone application. Analysis of independent F. pseudograminearum and F. graminearum FDB1 gene deletion mutants, as well as biochemical assays, demonstrated that the γ-lactamase enzyme, encoded by FDB1, catalyses the first step in detoxification of benzoxazolinones. Overall, our results support the notion that Fusarium pathogens that cause crown rot and head blight on wheat have adopted strategies to overcome host-derived chemical defences.
authors: Commonwealth Scientific and Industrial Research Organization (CSIRO) Agriculture Flagship, Queensland Bioscience Precinct, Brisbane, Queensland 4067, Australia; University of Queensland, School of Agriculture and Food Sciences, St. Lucia, Queensland 4067, Australia. Electronic address: Andrew.Kettle@csiro.au.
authors: Andrew J
authors: AJ
authors: Kettle
authors: Commonwealth Scientific and Industrial Research Organization (CSIRO) Agriculture Flagship, Queensland Bioscience Precinct, Brisbane, Queensland 4067, Australia.
authors: Jason
authors: J
authors: Carere
authors: University of Queensland, School of Agriculture and Food Sciences, St. Lucia, Queensland 4067, Australia; University of Western Australia, School of Plant Biology, Crawley 6009, Western Australia, Australia.
authors: Jacqueline
authors: J
authors: Batley
authors: Commonwealth Scientific and Industrial Research Organization (CSIRO) Agriculture Flagship, Queensland Bioscience Precinct, Brisbane, Queensland 4067, Australia.
authors: Aurelie H
authors: AH
authors: Benfield
authors: CSIRO Agriculture Flagship, Black Mountain, Canberra, Australian Capital Territory 2601, Australia.
authors: John M
authors: JM
authors: Manners
authors: Commonwealth Scientific and Industrial Research Organization (CSIRO) Agriculture Flagship, Queensland Bioscience Precinct, Brisbane, Queensland 4067, Australia; Queensland Alliance for Agriculture & Food Innovation, The University of Queensland, St. Lucia, Brisbane, Queensland 4067, Australia.
authors: Kemal
authors: K
authors: Kazan
authors: Commonwealth Scientific and Industrial Research Organization (CSIRO) Agriculture Flagship, Queensland Bioscience Precinct, Brisbane, Queensland 4067, Australia.
authors: Donald M
authors: DM
authors: Gardiner
mesh_terms: D000581:Amidohydrolases / Q000235:genetics / Q000378:metabolism*; D000627:Aminophenols / Q000378:metabolism; D001583:Benzoxazoles / Q000378:metabolism* / Q000494:pharmacology; D002384:Catalysis; D002523:Edible Grain / Q000382:microbiology*; D005670:Fusarium / Q000201:enzymology* / Q000235:genetics; D005800:Genes, Fungal; D008658:Inactivation, Metabolic; D012717:Sesquiterpenes / Q000378:metabolism*; D015533:Transcriptional Activation; D000094162:Phytoalexins
chemical_list: D000627:Aminophenols; D001583:Benzoxazoles; D012717:Sesquiterpenes; C027667:2-aminophenol; C017057:benzoxazolone; D000581:Amidohydrolases; C401943:gamma-lactamase; D000094162:Phytoalexins
keywords: Benzoxazolinone; Fusarium graminearum; Lactamase; Phenoxazinonel Fusarium pseudograminearum; Phytoalexin