N. Forthoffer et al., Induction and inactivation of a cytochrome P450 confering herbicide resistance in wheat seedlings, EUR J DRUG, 26(1-2), 2001, pp. 9-16
Citations number
33
Categorie Soggetti
Pharmacology & Toxicology
Journal title
EUROPEAN JOURNAL OF DRUG METABOLISM AND PHARMACOKINETICS
Cytochrome P450-dependent enzymes from wheat catalyze the oxidation of endo
genous compounds (lauric and oleic acids) and of several herbicides (diclof
op, chlortoluron, bentazon). Treatment of wheat seedlings with the safener,
naphthalic anhydride and with phenobarbital increases dramatically several
P450-dependent enzyme activities including diclofop and lauric acid hydrox
ylation. The parallel induction of lauric acid (omega -1)-hydroxylase and d
iclofop hydroxylase activities suggests that both compounds proceeds from t
he same or very similar forms of P450. To test whether either one or multip
le P450 forms are involved in these oxidations, we have designed selective
irreversible inhibitors of lauric acid (omega -1)-hydroxylase. Results of i
n vivo and in vitro experiments with acetylenic analogs of lauric acid (10-
and 11-dodecynoic acids) strongly suggest that a single P450 catalyzes bot
h laurate and diclofop hydroxylation. Treatment of wheat seedlings with the
se acetylenes results in a strong inhibition of the in vivo metabolism of d
iclofop although oxidation of chlortoluron and bentazon are not affected. O
ur results suggest that at least three distinct P450 forms are involved in
the detoxification process of the three herbicides. Interestingly, we also
demonstrate that herbicides themselves are potent inducers of the amount of
total P450 and laurate/diclofop hydroxylase activies. This increased capac
ity of wheat to detoxify the herbicide through the induction of P450 enzyme
s seems to be for a large extend the mechanism which confers a tolerance on
various herbicides.