Construction and analysis of cDNA libraries from the antennae of male and female cotton bollworms Helicoverpa armigera (Hübner) and expression analysis of putative odorant-binding protein genes

Two high-quality cDNA libraries were constructed from female and male antennae of the cotton bollworm Helicoverpa armigera (Hübner). The titers were approximately 2.0 × 10⁶ pfu/ml for females and 2.3 × 10⁶ pfu/ml for males, and this complies with the test requirement. From the libraries, 1750 male ESTs and 1640 female ESTs were sequenced and further analyzed. We identified 15 olfactory genes (12 are new), and 14 of them have the characteristic six conserved cysteine residues. With the exception of OBP9, all the genes were classified as classical OBP genes. By alignment and cluster analysis, the 14 classical OBPs were divided into pheromone binding protein (PBP) genes, odorant binding protein (OBP) genes, general odorant binding protein 1 (GOBP1) genes, general odorant binding protein 2 (GOBP2) genes and antennae binding protein (ABP) genes. Among these genes, we obtained three PBP genes (PBP1–PBP3) including two new PBP genes, one new ABP gene, nine new OBP genes (OBP1–OBP9), one known GOBP1 gene and one known GOBP2 gene. Furthermore, the expression patterns of these 14 classical OBP genes were investigated in various tissues by real-time quantitative polymerase chain reaction (qPCR). The results indicated that some OBP genes are expressed differently in different sexes and tissues, but most of them are highly expressed in antennae.