title: Leucine metabolism regulates TRI6 expression and affects deoxynivalenol production and virulence in Fusarium graminearum.
abstract: TRI6 is a positive regulator of the trichothecene gene cluster and the production of trichothecene mycotoxins [deoxynivalenol (DON)] and acetylated forms such as 15-Acetyl-DON) in the cereal pathogen Fusarium graminearum. As a global transcriptional regulator, TRI6 expression is modulated by nitrogen-limiting conditions, sources of nitrogen and carbon, pH and light. However, the mechanism by which these diverse environmental factors affect TRI6 expression remains underexplored. In our effort to understand how nutrients affect TRI6 regulation, comparative digital expression profiling was performed with a wild-type F. graminearum and a Δtri6 mutant strain, grown in nutrient-rich conditions. Analysis showed that TRI6 negatively regulates genes of the branched-chain amino acid (BCAA) metabolic pathway. Feeding studies with deletion mutants of MCC, encoding methylcrotonyl-CoA-carboxylase, one of the key enzymes of leucine metabolism, showed that addition of leucine specifically down-regulated TRI6 expression and reduced 15-ADON accumulation. Constitutive expression of TRI6 in the Δmcc mutant strain restored 15-ADON production. A combination of cellophane breach assays and pathogenicity experiments on wheat demonstrated that disrupting the leucine metabolic pathway significantly reduced disease. These findings suggest a complex interaction between one of the primary metabolic pathways with a global regulator of mycotoxin biosynthesis and virulence in F. graminearum.
authors.affiliation: Agriculture and Agri-Food Canada, Eastern Cereal Research Centre, Ottawa, K1A0C6, Canada.
authors.forename: Rajagopal
authors.initials: R
authors.lastname: Subramaniam
authors.affiliation: Agriculture and Agri-Food Canada, Eastern Cereal Research Centre, Ottawa, K1A0C6, Canada.
authors.forename: Swara
authors.initials: S
authors.lastname: Narayanan
authors.affiliation: Agriculture and Agri-Food Canada, Eastern Cereal Research Centre, Ottawa, K1A0C6, Canada.|Department of Biology, Carleton University, 1125 Colonel By, Ottawa, K1S5B6, Canada.
authors.forename: Sean
authors.initials: S
authors.lastname: Walkowiak
authors.affiliation: Agriculture and Agri-Food Canada, Eastern Cereal Research Centre, Ottawa, K1A0C6, Canada.
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.affiliation: Agriculture and Agri-Food Canada, Eastern Cereal Research Centre, Ottawa, K1A0C6, Canada.
authors.forename: Manisha
authors.initials: M
authors.lastname: Joshi
authors.affiliation: Agriculture and Agri-Food Canada, Eastern Cereal Research Centre, Ottawa, K1A0C6, Canada.
authors.forename: Hélène
authors.initials: H
authors.lastname: Rocheleau
authors.affiliation: Agriculture and Agri-Food Canada, Eastern Cereal Research Centre, Ottawa, K1A0C6, Canada.
authors.forename: Thérèse
authors.initials: T
authors.lastname: Ouellet
authors.affiliation: Agriculture and Agri-Food Canada, Eastern Cereal Research Centre, Ottawa, K1A0C6, Canada.
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Harris
mesh_terms: D000597:Amino Acids, Branched-Chain / Q000235:genetics / Q000378:metabolism; D019735:Carbon-Carbon Ligases / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D005670:Fusarium / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity*; D015966:Gene Expression Regulation, Fungal; D005838:Genotype; D007930:Leucine / Q000378:metabolism*; D053858:Metabolic Networks and Pathways / Q000235:genetics; D005810:Multigene Family; D009154:Mutation; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014255:Trichothecenes / Q000096:biosynthesis*; D014908:Triticum / Q000382:microbiology
chemical_list: D000597:Amino Acids, Branched-Chain; D005656:Fungal Proteins; D014157:Transcription Factors; D014255:Trichothecenes; C046760:15-acetyldeoxynivalenol; D019735:Carbon-Carbon Ligases; C021573:methylcrotonoyl-CoA carboxylase; D007930:Leucine; C007262:deoxynivalenol