Dissecting the insecticide-resistance- associated cytochrome P450 gene Cyp6g1.
BACKGROUND
The cytochrome P450 gene Cyp6g1 is overtranscribed in all field isolates of DDT-resistant Drosophila melanogaster (Meigen) and confers a fitness advantage when inherited via the female. Overtranscription is associated with the insertion of an Accord transposable element into the 5' end of the resistance allele. Here the authors attempt to dissect the transcription of the P450 gene in order to understand why resistance confers an advantage rather than the expected cost.


RESULTS
Using a transgenic UAS:GAL4 reporter, the authors document the overexpression patterns of green fluorescent protein (GFP) in the fat body, midgut and Malpighian tubules driven by flies carrying the resistant 5' construct. Knockout of Cyp6g1 via RNAi decreases both the level of Cyp6g1 transcript and the metabolism of the artificial substrate MROD (methyl ether resorufin, Sigma M1544). RNAi does not, however, significantly increase the susceptibility of susceptible flies to DDT. Finally, quantification of Cyp6g1 RNA in embryos laid by resistant females indicates that they pass on more Cyp6g1 RNA to their progeny than their susceptible counterparts.


CONCLUSIONS
These results help explain why the eggs and larvae of resistant females enjoy a fitness benefit rather than a cost, and suggest that the provisioning of Cyp6g1 RNA to embryos provides a direct, but uncharacterised, fitness benefit.
McCart
Caroline
C
Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK.
Ffrench-Constant
Richard H
RH
D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000187:drug effects / Q000196:embryology / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation; D007305:Insecticide Resistance; D030781:Organisms, Genetically Modified; D034622:RNA Interference
D029721:Drosophila Proteins; D003577:Cytochrome P-450 Enzyme System; C446928:Cyp6g1 protein, Drosophila