Purification and characterisation of a family of glutathione transferases with roles in herbicide detoxification in soybean (Glycine max L.); selective enhancement by herbicides and herbicide safeners

Glutathione transferases in soybean (GmGSTs) involved in herbicide detoxification in cell suspension cultures were purified by S-hexylglutathione affinity chromatography and resolved by a combination of HPLC and SDS-PAGE into 11 polypeptides. Analysis by Western blotting using antisera raised to three previously characterised tau (GmGSTU) class subunits demonstrated that five polypeptides were related to GmGSTU1, three to GmGSTU2, and one to Gm GSTU3. Plants contained a simpler profile of polypeptides, with a single GmGSTU2-like polypeptide predominating. With respect to herbicide detoxification, two GmGSTU2-related polypeptides dominated the activity toward the chloroacetanilide acetochlor, while an unclassified subunit was uniquely associated with the detoxification of diphenyl ethers (acifluorfen, fomesafen). The inducibility of the different GST subunits was determined in soybean plants exposed to photobleaching diphenyl ethers and the safeners naphthalic anhydride and dichlormid. GmGSTU3, a GmGSTU1-like polypeptide, and thiol (homoglutathione) content were induced by all chemical treatments, while two uncharacterised subunits were only induced in plants showing photobleaching.