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Glutathione transferases involved in herbicide detoxification in the leaves of Setaria faberi (giant foxtail)
Author(s) -
Hatton Pamela J.,
Cummins Ian,
Cole David J.,
Edwards Robert
Publication year - 1999
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.1999.105103.x
Subject(s) - foxtail , setaria , isozyme , atrazine , glutathione s transferase , metolachlor , glutathione , alachlor , biology , protein subunit , biochemistry , enzyme , botany , gene , agronomy , pesticide
Setaria faberi (giant foxtail) is a major grass weed of maize in North America and can prove difficult to control using selective herbicides. In grasses, tolerance to the chloro‐ s ‐triazine and chloroacetanilide classes of selective herbicides is associated with their rapid detoxification by glutathione conjugation catalysed by glutathione transferases (GSTs, EC 2.5.1.18). We were therefore interested in characterising the GSTs in S. faberi and comparing them with the corresponding enzymes in maize. Four S. faberi GST isoenzymes ( Sfa GSTs 1 to 4) with activities toward the triazine herbicide atrazine, the chloroacetanilide herbicides metolachlor and alachlor and the diphenyl ether herbicide fluorodifen were purified from the foliage of young plants. These GSTs detoxified herbicides with similar efficiencies to those determined for GST isoenzymes from maize, but their levels of expression in the leaves were 20‐fold lower than those reported in the crop. All Sfa GSTs were composed of two subunits and the 28 kDa subunit of the isoenzyme Sf aGST1 reacted strongly to an antiserum raised to the maize theta‐type GST Zm GSTI‐II. Sfa GST1 also appeared to be very similar in substrate specificity to the major maize GST Zm GSTI‐I. The similarity of Sfa GST1 and Zm GSTI subunits was confirmed by RT‐PCR using primers specific to Zm GSTI, with a 370 bp DNA amplification product from S. faberi showing 88% identity at the nucleotide level to the corresponding sequence of Zm GSTI. However, Sfa GSTs also differed significantly from Zm GSTs. Unlike maize, only one isoenzyme, Sfa GST2, detoxified chloroacetanilides. Also, Sfa GST3 and Sfa GST4 resembled tau‐type GSTs from maize in showing high activities toward fluorodifen, but these Sfa GSTs were not recognised by an antiserum raised to the maize tau‐type GST Zm GSTV‐VI. Sfa GST4 also differed from the Zm GSTs described to date in showing high activities toward atrazine. Our results demonstrate that while some GSTs are conserved in grass crops and weeds, others are quite different.