Plant Physiol, November 2002, Vol. 130, pp. 1497-1505
Induction of Glutathione S-Transferases in
Arabidopsis by Herbicide Safeners1
Ben P.
DeRidder,
David P.
Dixon,
Douglas J.
Beussman,
Robert
Edwards, and
Peter B.
Goldsbrough*
Departments of Horticulture and Landscape Architecture (B.P.D.,
P.B.G.) and Medicinal Chemistry and Molecular Pharmacology (D.J.B.),
Purdue University, West Lafayette, Indiana 47907-1165; and School
of Biological and Biomedical Sciences, University of Durham, Durham DH1
3LE, United Kingdom (D.P.D., R.E.)
Herbicide safeners increase herbicide tolerance in cereals
but not in dicotyledenous crops. The reason(s) for this difference in
safening is unknown. However, safener-induced protection in cereals is
associated with increased expression of herbicide detoxifying enzymes,
including glutathione S-transferases (GSTs). Treatment of Arabidopsis seedlings growing in liquid medium with various safeners
similarly resulted in enhanced GST activities toward a range of
xenobiotics with benoxacor, fenclorim, and fluxofenim being the most
effective. Safeners also increased the tripeptide glutathione content
of Arabidopsis seedlings. However, treatment of Arabidopsis plants with
safeners had no effect on the tolerance of seedlings to
chloroacetanilide herbicides. Each safener produced a distinct profile
of enhanced GST activity toward different substrates suggesting a
differential induction of distinct isoenzymes. This was confirmed by
analysis of affinity-purified GST subunits by two-dimensional sodium
dodecyl sulfate-polyacrylamide gel electrophoresis. AtGSTU19, a tau class GST, was identified as a dominant
polypeptide in all samples. When AtGSTU19 was expressed in
Escherichia coli, the recombinant enzyme was highly
active toward 1-chloro-2,4-dinitrobenzene, as well as chloroacetanilide
herbicides. Immunoblot analysis confirmed that AtGSTU19 was
induced in response to several safeners. Differential induction of tau
GSTs, as well as members of the phi and theta classes by safeners, was
demonstrated by RNA-blot analysis. These results indicate that,
although Arabidopsis may not be protected from herbicide injury by
safeners, at least one component of their detoxification systems is
responsive to these compounds.
1
This work was supported in part by the U.S.
Department of Agriculture (National Needs fellowship grant).
*
Corresponding author; e-mail goldsbrough{at}hort.purdue.edu; fax
765-494-0391.
© 2002 American Society of Plant Biologists
