Herbicide safeners and glutathione metabolism

Herbicide safeners are chemicals which protect crop plants from injury by certain herbicides, without affecting weed control efficacy of the herbicides. The protective mechanism of herbicide safeners has not yet been fully elucidated, but there is increasing evidence that safeners act by selectively enhancing herbicide detoxification in crop plants. To date, two main detoxification pathways have been related to the mode of action of herbicide safeners. The first includes oxidation and subsequent glucose conjugation, mediated by cytochrome P450-dependent monooxygenases and UDP-glucosyltransferases, respectively. This pathway appears to be important predominantly in safener protection to aryloxyphenoxypropionate and sulfonylurea herbicides. The second pathway represents the conjugation of thiocarbamate sulfoxides and chloroacetanilide herbicides with glutathione. This mechanism is accomplished by either elevating the levels of reduced glutathione or the activity of glutathione S-transferase, or both. Since glutathione has been reported to be involved in several stress situations of plants its function associated with safener-induced herbicide tolerance will be discussed in more detail in this review.