Cytochrome P-450 Field Insecticide Tolerance and Development of Laboratory Resistance in Grape Vine Populations of Drosophila melanogaster(Diptera: Drosophilidae)

Abstract

Studies were conducted between 1993 and 1996 using 3 natural grape vine populations, 1 susceptible laboratory strain, and 1 resistant selected strain of Drosophila melanogaster L. In vitro monooxygenase activity (ethoxycoumarine-O-deethylation) (ECOD) was recorded from microsomal fractions of all strains. Results varied over a 6-fold range between susceptible laboratory Canton and resistant selected RDDT strains and over a 2-fold range between the Canton strain and natural populations of flies. Few significant variations of ECOD activity were detected among the natural populations despite many insecticide treatments, but activities were significantly correlated with toxicological tolerance to 5 of the 15 insecticides (deltamethrin, fipronil, chlorpyriphos ethyl, DDT, and diazinon). Moreover, immunoblotting responses of microsomal protein encoded by Cyp6A2 showed that the levels of expression were quantitatively correlated with toxicological tolerance to almost the same group of insecticides (deltamethrin, fipronil, chlorpyriphos ethyl, DDT, fenvalerate, and fenthion). However, the level of CYP6A2 expression in some natural strains (still weakly resistant) was almost comparable with one of the resistant strains. In vivo monooxygenase activity recorded in individual abdomens of flies showed that frequency distributions of ECOD activity in natural populations overlapped those of the resistant and laboratory strains, which were much narrower. Substantial and fast frequency changes (of the narrowness) that obtained in laboratory were related to either the time of rearing of 1 of the natural populations or selecting this population with an insecticide that has a toxicology correlated with both of the monooxygenase signs measured. Perspectives on using the CYP6A2 expression and ECOD activity for detecting a resistance mechanism by cytochrome P450 in field populations are discussed.

Exposure to Sublethal Doses of Fipronil and Thiacloprid Highly Increases Mortality of Honeybees Previously Infected by Nosema ceranae

“…In insects, ECOD and GST activities have often served as convenient measures of overall phases I and II metabolizing enzyme activities. In addition, levels of ECOD and GST activities have been associated with sensitivity to insecticides [33], [34]. Our results showed that ECOD activity remained unchanged at 10 days p.i, in fat body and midgut whereas GST activity increased significantly in both tissues.…”

Genome‐wide analysis of phenobarbital‐inducible genes in Drosophila melanogaster

“…Increases in Cyp6a2 mRNA (and the resultant Cyp6a2 protein) have been associated with metabolic pesticide resistance both in terms of over‐transcription of this gene and in terms of changes in catalytic properties. Cyp6a2 expression levels in pesticide resistant and susceptible strains of Drosophila have been measured using western blots (Bride et al ., 1997) and a correlation was observed between Cyp6a2 titre and resistance (Bride et al ., 1997). However, Cyp6a2 expression level was not a predictor of resistance level.…”

Fipronil metabolism, oxidative sulfone formation and toxicity among organophosphate- and carbamate-resistant and susceptible western corn rootworm populations

“…The documentation of this phenomenon helps to explain the relatively high toxicity of fipronil and why, in numerous insect groups, fipronil typically retains its toxicity to populations which do not appear to be in possession of altered GABA‐gated chloride/ionopore target sites 2–4. 19, 20 The similar toxicity of fipronil and fipronil‐sulfone observed here also helps to explain the apparent lack of effects by PBO in bioassays (ie by inhibiting sulfone formation the net toxicity is not compromised). More general speculation of this relationship on a broad scale may be inappropriate at this time, but experimentation with a diverse array of insect groups would probably provide valuable information.…”