Abstract
Herbicide safeners protect cereal crops from herbicide injury, in part by inducing expression of glutathione S-transferases (GSTs). Safeners also induce GSTs in Arabidopsis but fail to protect against herbicide injury. This may result either from induction of GSTs that cannot detoxify herbicides efficiently or from a failure to express GSTs in the appropriate tissues. To examine these possibilities we have developed transgenic Arabidopsis expressing GSTs from Arabidopsis (AtGSTU19), Triticum tauschii (TtGSTU1), or maize (ZmGST4) under the control of the 35S promoter. Plants expressing ZmGST4 are highly tolerant to various chloroacetamide herbicides in germination assays and with foliar application tests. These plants also show significant GSH-conjugating activity with dimethenamid. In contrast, plants that overexpress AtGSTU19 show increased GST activity with CDNB but are unaltered in herbicide tolerance. Therefore, the inability of safeners to protect Arabidopsis results from the failure to induce GSTs that can efficiently metabolize chloroacetamide herbicides.
