Abstract: In order to study the molecular mechanisms of insecticide resistance in Helicoverpa armigera (Hübner), a fulllength carboxylesterase cDNA was firstly cloned from H. armigera using RT-PCR and rapid amplification of cDNA ends (RACE) strategies. Sequence analysis revealed that this gene contains a 1 794 bp ORF, a 129 bp 5′ UTR and 139 bp 3′UTR, encoding a 597-amino-acid protein. The predicted molecular weight and isoelectric point of this carboxylesterase were 67.1 kD and 4.92, respectively. This gene was deposited in GenBank under the accession no. EF547544. Homology analysis showed that this carboxylesterase is most similar to that from Spodoptera litura with 60% amino acid identity. The results of semi-quantitative RT-PCR showed that this gene was highly expressed in the midgut, low expressed in fat body and gonad and not expressed in head. It is inferred that this carboxylesterase gene may be involved in detoxification of xenobiotics.

Key words: Helicoverpa armigera, carboxylesterase, RACE, sequence analysis, tissue expression