Analysis of Enantioselective Biochemical, Physiological, and Transcriptional Effects of the Chiral Herbicide Diclofop Methyl on Rice Seedlings

Diclofop methyl (DM) is a chiral herbicide that is widely used as a racemic mixture. This study analyzed the enantioselective effects of R- and S-DM on rice at the physiological and molecular levels. DM exerts an enantioselective effect on rice growth, reactive oxygen substance (ROS) formation, and antioxidant gene expression, with R-DM acting as a more potent stressor than S-DM. An analysis of chlorophyll fluorescence demonstrated that photosynthesis process was more strongly inhibited by R-DM than by S-DM. Microarray results showed that many metabolic pathways, including starch and sucrose metabolism, oxidative phosphorylation, and amino acid biosynthesis and metabolism, were affected by DM in an enantioselective manner. These results suggest that R-DM is more active to plant growth than S-DM and that this activity is induced not only by repression of fatty acid synthesis but also by R-DM affecting the transcription of genes in other metabolic pathways in an enantioselective manner.