Expression and induction of three family 4 cytochrome P450 (CYP4)* genes identified from insecticide-resistant and susceptible western corn rootworms, Diabrotica virgifera virgifera

We have previously determined that cytochrome P450-based oxidation is invol ved in resistance to the insecticides methyl parathion and carbaryl in geog raphically distinct Nebraska western corn rootworm populations. Three new f amily 4 cytochrome P450 (CYP4) gene fragments (CYP4AJ1, CYP4G18 and CYP4AK1 ) were cloned and sequenced from insecticide-resistant and -susceptible wes tern corn rootworms. Insecticide bioassays indicated the resistant populati on employed in this study was significantly resistant to the insecticides m ethyl parathion and carbaryl. CYP4AJ1 and CYP4G18 were cloned from both gen omic PCR and RT-PCR products, although only CYP4AJ1 contains an intronic re gion. Alignments of inferred amino acid sequences with other homologous Ins ect CYP4 genes indicates a high degree of similarity. Northern analysis con currently employing mixed probes representing each of the three rootworm CY P4 fragments identified increased mRNA transcript signals (i) in resistant rootworms and (ii) following induction by the P450 inducer pentamethyl benz ene, These results support our previous documentation of P450-based insecti cide resistance and suggest increased CYP4 transcript abundance can serve a s a molecular resistance-associated marker.