title: Unraveling the toxicity mechanisms of the herbicide diclofop-methyl in rice: modulation of the activity of key enzymes involved in citrate metabolism and induction of cell membrane anion channels.
abstract: Residual soil concentrations of the herbicide diclofop-methyl (DM) can be toxic to other nontarget plant species, but the toxicity mechanisms at play are not fully understood. In the present study, we analyzed the toxic effect of DM on root growth and metabolism in the rice species Oryza sativa. The results show that a 48-h exposure to a trace level (5 μg/L) of DM inhibits rice root growth by almost 70%. A 48-h exposure to 5 μg/L DM also leads to an ≈2.5-fold increase in citrate synthase (CS) activity (and CS gene transcription) and an ≈2-fold decrease in the citrate lyase gene transcripts, which lead to an increase in the intracellular concentration of citrate and in citrate exudation rate. Addition of a specific inhibitor of cell membrane anion channel, anthracene-9-carboxylic acid, decreased citrate release in the culture, suggesting that DM-induced citrate loss from the cells is mediated by a specific membrane-bound channel protein. This study brings new insights into the key biochemical mechanisms leading to DM toxicity in rice.
authors.affiliation: College of Biological and Environmental Engineering and ∥Department of Food Science and Technology, Zhejiang University of Technology , Hangzhou 310032, P. R. China.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Ding
authors.forename: Haiping
authors.initials: H
authors.lastname: Lu
authors.forename: Michel
authors.initials: M
authors.lastname: Lavoie
authors.forename: Jun
authors.initials: J
authors.lastname: Xie
authors.forename: Yali
authors.initials: Y
authors.lastname: Li
authors.forename: Xiaolu
authors.initials: X
authors.lastname: Lv
authors.forename: Zhengwei
authors.initials: Z
authors.lastname: Fu
authors.forename: Haifeng
authors.initials: H
authors.lastname: Qian
mesh_terms: D001692:Biological Transport; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002950:Citrate (si)-Synthase / Q000235:genetics / Q000378:metabolism*; D019343:Citric Acid / Q000378:metabolism*; D055768:Halogenated Diphenyl Ethers / Q000633:toxicity*; D006540:Herbicides / Q000633:toxicity*; D012275:Oryza / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D050994:Voltage-Dependent Anion Channels / Q000235:genetics / Q000378:metabolism
chemical_list: D055768:Halogenated Diphenyl Ethers; D006540:Herbicides; D010940:Plant Proteins; D050994:Voltage-Dependent Anion Channels; D019343:Citric Acid; C012891:dichlorfop-methyl; D002950:Citrate (si)-Synthase
keywords: cell wall; citrate; diclofop-methyl; herbicide; organic acid; rice