Overexpression of CYP4G19 associated with a pyrethroid-resistant strain of the German cockroach, Blattella germanica (L.)

Abstract

A new cytochrome P450 gene, CYP4G19, was identified and isolated as a differentially expressed gene between insecticide susceptible ACY and resistant Apyr-R German cockroach strains using PCR-selected subtractive hybridization and cDNA array techniques. The cDNA sequence of CYP4G19 has an open ready frame of 1638 nucleotides encoding a putative protein of 546 amino acid residues. Sequence analysis shows that CYP4G19 putative protein contains (1) a highly hydrophobic N terminus, (2) a P450 protein signature motif, FXXGXRXCXG, known to be an important ligand for heme binding, and (3) an important characteristic motif, EVDTFMFEGHDTT, for the family 4. Northern blot analysis indicated that levels of CYP4G19 expression were low in eggs, nymphs, and adults of the susceptible ACY strain with a similar expression pattern. The expression of CYP4G19 in the resistant Apyr-R strain was developmentally regulated, with very low expression in eggs, increasing in nymphs, and reaching a maximum in both female and male adults. Comparison of CYP4G19 expression between ACY and Apyr-R strains indicated that there was no difference in their eggs, but expression was higher (∼1.7-fold) in the nymphs and much higher (∼5-fold) in the male and female adults of the Apyr-R strain. Levels of CYP4G19 mRNA were readily detectable in head+thorax tissues and increased (∼5-fold) in the abdomens of the ACY strain. In the Apyr-R strain, however, levels of CYP4G19 mRNA were relatively low in head+thorax tissues and were about 7-fold increase in the abdomen. Although expression patterns of CYP4G19 in head+thorax and abdomen tissues were similar (i.e. lower in head+thorax tissues and higher in abdomen tissues) in both the ACY and Apyr-R strains, the overexpression was more evident in the Apyr-R strain in both head+thorax and abdomen tissues than in the ACY strain.