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A role for glutathione transferases functioning as glutathione peroxidases in resistance to multiple herbicides in black‐grass
Author(s) -
Cummins Ian,
Cole David J.,
Edwards Robert
Publication year - 1999
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1999.00452.x
Subject(s) - glutathione , resistance (ecology) , glutathione transferase , glutathione peroxidase , peroxidase , biology , chemistry , biochemistry , agronomy , enzyme
Summary Black‐grass ( Alopecurus myosuroides ) is a major weed of wheat in Europe, with several populations having acquired resistance to multiple herbicides of differing modes of action. As compared with herbicide‐susceptible black‐grass, populations showing herbicide cross‐resistance contained greatly elevated levels of a specific type I glutathione transferase (GST), termed Am GST2, but similar levels of a type III GST termed Am GST1. Following cloning and expression of the respective cDNAs, Am GST2 differed from Am GST1 in showing limited activity in detoxifying herbicides but high activities as a glutathione peroxidase (GPOX) capable of reducing organic hydroperoxides. In contrast to Am GST2, other GPOXs were not enhanced in the herbicide‐resistant populations. Treatment with a range of herbicides used to control grass weeds in wheat resulted in increased levels of hydroperoxides in herbicide‐susceptible populations but not in herbicide‐resistant plants, consistent with Am GST2 functioning to prevent oxidative injury caused as a primary or secondary effect of herbicide action. Increased Am GST2 expression in black‐grass was associated with partial tolerance to the peroxidizing herbicide paraquat. The selective enhancement of Am GST2 expression resulted from a constitutively high expression of the respective gene, which was activated in herbicide‐susceptible black‐grass in response to herbicide safeners, dehydration and chemical treatments imposing oxidative stress. Our results provide strong evidence that GSTs can contribute to resistance to multiple herbicides by playing a role in oxidative stress tolerance in addition to detoxifying herbicides by catalysing their conjugation with glutathione.