Molecular characters and expression analysis of the gene encoding eclosion hormone from the Asian corn borer, Ostrinia furnacalis.

Using rapid amplification of cDNA ends (RACE), the cDNA encoding eclosion hormone (EH) was cloned from the brain of Ostrinia furnacalis. The full Osf-EH cDNA is 986 bp and contains a 267 bp open reading frame encoding an 88 amino acid preprohormone, which including a hydrophobic 26 amino acid signal peptide and a 62 amino acid mature peptide. The mature Osf-EH shows high identity with Manduca sexta (95.2%), Helicoverpa armigera (91.9%) and Bombyx mori (85.5%), but low identify with Tribolium castaneum (63.6%), Drosophila melanogaster (56.5%) and Apis mellifera (54.8%). Using the HMMSTR Prediction Server, the 3D structure of Osf-EH was modeled. There are four beta-turns and three alpha-helixes predicted in Osf-EH, with the pattern of beta-beta-alpha-alpha-beta-beta-alpha. Northern blot analysis indicated a 1.0 kb transcript present only in the brain. The Osf-EH mRNA can not be detected in other neural tissues, such as the suboesophageal ganglion, thoracic ganglion, abdominal ganglion and other non-neural tissues, such as the midgut, fat body and epidermis. The Osf-EH mRNA content in the brain was measured using the combined method of quantitative RT-PCR and Southern blotting, which reached its highest level the day before the molt.