Abstract: 【Aim】 This study aims to reveal the tissue expression patterns of the odorant binding protein (OBP) gene HarmOBP16 in the cotton bollworm, Helicoverpa armigera, and the binding properties of its recombinant protein with plant volatiles. 【Methods】 According to the antenna transcriptome data, the OBP gene was cloned from the antennae of H. armigera adults and subjected to bioinformatical and phylogenetic analysis. The tissue expression patterns of the gene in adult head (without antennae and probosis), thorax, abdomen, legs, wings, antennae and proboscis were assayed by qPCR. The recombinant protein was expressed and purified with prokaryotic expression system. The binding characteristics of this recombinant protein to 85 candidate plant volatiles were measured by fluorescence competitive binding assay. 【Results】 An atypical OBP gene, HarmOBP16 (GenBank accession no.: JQ753074), was identified and cloned from the antennae of H. armigera adults by PCR. It contains a 441 bp open reading frame (ORF) encoding a protein of 146 amino acids with 10 conserved cysteine residues and the isoelectric point value of 6.87. The tissue expression patterns showed that HarmOBP16 was highly expressed in wings of the female adults. The competitive fluorescence binding assay of the expressed and purified recombinant HarmOBP16 showed that HarmOBP16 exhibited higher binding affinities to geranylacetone (Ki=14.2 μmol/L), β-ionone (Ki=15.2 μmol/L), octyl aldehyde (Ki=15.3 μmol/L), (+/-)-linalool (Ki=16.8 μmol/L), (R)-(+)-limonene (Ki=14.9 μmol/L), and (+)-β-pinene (Ki=17.3 μmol/L). 【Conclusion】 The results suggest that HarmOBP16 may play a role in the host seeking of H. armigera, which may provide a potential molecular target for the development of attractants or repellents in H. armigera.

Key words: Helicoverpa armigera; odorant binding protein, tissue expression patterns, in vitro expression, competitive fluorescence binding assay