title: Localisation of the benzimidazole fungicide binding site of Gibberella zeae β2-tubulin studied by site-directed mutagenesis.
abstract: BACKGROUND
  The efficacy of benzimidazole fungicides is often limited by resistance, and this is the case with the use of carbendazim for controlling Fusarium head blight caused by Gibberella zeae (Schwein.) Petch (anamorph Fusarium graminearum). Recent studies have shown that carbendazim resistance in field strains of G. zeae is associated with mutations in the β(2)-tubulin gene. The aims of the present study were to validate this mechanism and research the binding sites of carbendazim on β(2)-tubulin.
  
  
  RESULTS
  This work used site-directed mutagenesis followed by gene replacement to change the β(2)-tubulin gene of a carbendazim-sensitive field strain of G. zeae at residues 50, 167, 198 or 200. The transformants were confirmed and tested for their sensitivity to carbendazim. All the mutants were resistant to carbendazim, but the level of resistance differed depending on the mutation. Biological characteristics did not differ between the field strain and the site-directed mutants. A three-dimensional model of β(2)-tubulin was constructed, and the possible carbendazim binding site was analysed.
  
  
  CONCLUSIONS
  Mutations at codons 50, 167, 198 and 200 of G. zeae β(2)tub could cause resistance to carbendazim, and these codons may form a binding pocket.
authors.affiliation: College of Plant Protection, Nanjing Agricultural University, Key Laboratory of Monitoring and Management of Crop Diseases and Pest Insects, Ministry of Agriculture, Nanjing, China.
authors.forename: JianBo
authors.initials: J
authors.lastname: Qiu
authors.forename: JianQiang
authors.initials: J
authors.lastname: Xu
authors.forename: JunJie
authors.initials: J
authors.lastname: Yu
authors.forename: ChaoWei
authors.initials: C
authors.lastname: Bi
authors.forename: ChangJun
authors.initials: C
authors.lastname: Chen
authors.forename: MingGuo
authors.initials: M
authors.lastname: Zhou
mesh_terms: D001562:Benzimidazoles / Q000494:pharmacology*; D001665:Binding Sites; D025141:Drug Resistance, Fungal; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D005659:Fungicides, Industrial / Q000494:pharmacology*; D005874:Gibberella / Q000737:chemistry / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011485:Protein Binding; D014404:Tubulin / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism
chemical_list: D001562:Benzimidazoles; D005656:Fungal Proteins; D005659:Fungicides, Industrial; D014404:Tubulin; C031000:benzimidazole