N. Liu et Jg. Scott, INCREASED TRANSCRIPTION OF CYP6D1 CAUSES CYTOCHROME-P450 MEDIATED INSECTICIDE RESISTANCE IN-HOUSE FLY, Insect biochemistry and molecular biology, 28(8), 1998, pp. 531-535
Insecticide resistance is a major problem that continues to plague eff
orts to control pests of animals and crops. An important mechanism by
which insects become resistant to insecticides is via increased detoxi
fication mediated by the cytochrome P450 microsomal monooxygenases (mo
nooxygenases). One of the fundamental gaps in our knowledge about this
resistance mechanism is an understanding of how insects express high
levels of the specific cytochrome P450(s) responsible for. resistance.
One. such P450, CYP6D1, causes resistance to pyrethroid insecticides
in the house fly and is expressed at 9-fold higher levels (mRNA and pr
otein) in the Learn Pyrethroid Resistant (LPR) strain (compared to sus
ceptible strains). The relative stability of CYP6D1 mRNA in resistant
and susceptible strains was measured following inhibition of transcrip
tion with actinomycin D. The same time course of decrease in CYP6D1 mR
NA abundance was detected in both strains indicating that the high lev
el of expression of CYP6D1 in LPR is not due to increased stability of
the mRNA. The comparative rates of transcription of CYP6D1 were measu
red using an in vitro run-on transcription assay. The relative amount
of CYP6D1 transcript produced in this assay was 10-fold greater in the
LPR strain compared to the susceptible strain. This demonstrates that
increased transcription of CYP6D1 is an underlying cause of monooxyge
nase-mediated insecticide resistance. The increased rate of transcript
ion of CYP6D1 in the resistant strain (LPR) is controlled by two facto
rs: one on autosome 1 and another on autosome 2. (C) 1998 Elsevier Sci
ence Ltd. All rights reserved.