Abstract: The full-length cDNA encoding a chemosensory protein (CSP) was isolated from the antenna of Helicoverpa assulta by reverse transcription polymerase chain reaction (RT-PCR).This PCR fragment was further cloned and sequenced. The results showed that the CSP gene in H. assulta was 384 bp in size (registered in GenBank with the accession number DQ285667) and encoded 127 amino acid residues. The N-terminus hydrophobic region predicted containing of 16 amino acid residues within the Has-CSP displayed the characteristic features of a signal peptide. Thus the predicted mature weight (MW) is 12.97 kD and isoelectric point (IP) 5.32. The CSP gene was then constructed into the expression vector pGEX-4T₂ for overexpression in prokaryotic cells. The SDS-PAGE analysis indicated that the CSP gene was expressed in Escherichia coli BL21. The Western blot further confirmed this result. The expressed fusion protein in BL21 was found to be about 39 kD, consistent with the predicted result.

Key words: Helicoverpa assulta, chemosensory protein, gene cloning, sequencing, prokaryotic expression