title: Enantioselective phytotoxicity of the herbicide imazethapyr on the response of the antioxidant system and starch metabolism in Arabidopsis thaliana.
abstract: BACKGROUND
  The enantiomers of a chiral compound possess different biological activities, and one of the enantiomers usually shows a higher level of toxicity. Therefore, the exploration of the causative mechanism of enantioselective toxicity is regarded as one of primary goals of biological chemistry. Imazethapyr (IM) is an acetolactate synthase (ALS)-inhibiting chiral herbicide that has been widely used in recent years with racemate. We investigated the enantioselectivity between R- and S-IM to form reactive oxygen species (ROS) and to regulate antioxidant gene transcription and enzyme activity.
  
  
  RESULTS
  Dramatic differences between the enantiomers were observed: the enantiomer of R-IM powerfully induced ROS formation, yet drastically reduced antioxidant gene transcription and enzyme activity, which led to an oxidative stress. The mechanism by which IM affects carbohydrate metabolism in chloroplasts has long remained a mystery. Here we report evidence that enantioselectivity also exists in starch metabolism. The enantiomer of R-IM resulted in the accumulation of glucose, maltose and sucrose in the cytoplasm or the chloroplast and disturbed carbohydrates utilization.
  
  
  CONCLUSIONS
  The study suggests that R-IM more strongly retarded plant growth than S-IM not only by acting on ALS, but also by causing an imbalance in the antioxidant system and the disturbance of carbohydrate metabolism with enantioselective manner.
authors.affiliation: College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou, People's Republic of China.
authors.forename: HaiFeng
authors.initials: H
authors.lastname: Qian
authors.forename: Tao
authors.initials: T
authors.lastname: Lu
authors.forename: XiaoFeng
authors.initials: X
authors.lastname: Peng
authors.forename: Xiao
authors.initials: X
authors.lastname: Han
authors.forename: ZhengWei
authors.initials: Z
authors.lastname: Fu
authors.forename: WeiPing
authors.initials: W
authors.lastname: Liu
mesh_terms: D000095:Acetolactate Synthase / Q000037:antagonists & inhibitors; D000975:Antioxidants / Q000378:metabolism*; D017360:Arabidopsis / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D006540:Herbicides / Q000737:chemistry / Q000494:pharmacology*; D009539:Nicotinic Acids / Q000737:chemistry / Q000494:pharmacology*; D013213:Starch / Q000378:metabolism*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
chemical_list: D000975:Antioxidants; D006540:Herbicides; D009539:Nicotinic Acids; C093630:imazethapyr; D013213:Starch; D000095:Acetolactate Synthase