title: Molecular bases for resistance to acetyl-coenzyme A carboxylase inhibitor in Japanese foxtail (Alopecurus japonicus).
abstract: BACKGROUND
  Haloxyfop-R-methyl is a widely used herbicide to control Poaceae weeds. Alopecurus japonicus, a widespread annual grass, can no longer be controlled by haloxyfop-R-methyl after continuous use of this herbicide for several years.
  
  
  RESULTS
  Dose-response experiments have established that the Js-R biotype of A. japonicas has evolved resistance to aryloxyphenoxypropionates (APPs). Target-site enzyme sensitivity experiments have established that the haloxyfop (free acid) rate causing 50% inhibition of acetyl-CoA carboxylase (ACCase) activity (I(50)) for the resistant (Js-R) biotype is 11 times higher than that for the susceptible (Js-S) biotype. In many cases, resistance to ACCase-inhibiting herbicides is due to a resistant ACCase enzyme. Full-length DNA and mRNA sequences of the plastidic ACCase gene were amplified. Eight single-nucleotide differences were detected in this region. Four of the nucleotide changes were silent mutations. However, the other four nucleotide mutations caused four amino acid substitutions, replacing Arg-1734 with Gly, Met-1738 with Leu, Thr-1739 with Ser and Ile-2041 with Asn in the R biotype respectively; the substitution at position 2041 had been reported, while the other three had not.
  
  
  CONCLUSIONS
  The ACCase in the Js-R biotype was less susceptible to haloxyfop-R-methyl than that in the Js-S biotype. Moreover, the amino acid substitution of Ile-2041 with Asn might confer resistance to haloxyfop-R-methyl in A. japonicas.
authors.affiliation: College of Plant Protection, Nanjing Agricultural University, Nanjing, China.
authors.forename: Huaiwu
authors.initials: H
authors.lastname: Tang
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.forename: Liyao
authors.initials: L
authors.lastname: Dong
authors.forename: Aibin
authors.initials: A
authors.lastname: Dong
authors.forename: Bo
authors.initials: B
authors.lastname: Lü
authors.forename: Xudong
authors.initials: X
authors.lastname: Zhu
mesh_terms: D000103:Acetyl-CoA Carboxylase / Q000037:antagonists & inhibitors* / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001483:Base Sequence; D053209:Herbicide Resistance; D006540:Herbicides / Q000494:pharmacology; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D010940:Plant Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics* / Q000378:metabolism; D006109:Poaceae / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics
chemical_list: D006540:Herbicides; D010940:Plant Proteins; D000103:Acetyl-CoA Carboxylase