Isolation, endocrine regulation and transcript distribution of a putative primary JH-responsive gene from the pine engraver, Ips pini (Coleoptera: Scolytidae)

We isolated a cDNA of unknown function from a juvenile hormone III (JH III)-treated male midgut cDNA library prepared from the pine engraver beetle, Ips pini, and examined its genomic structure. The gene, tentatively named “Ipi10G08”, encoded a 410 amino acid translation product that shared 26-37% identity with unannotated matches from several insects. Semi-quantitative RT-PCR analysis of Ipi10G08 following application of a 10 μg dose of JH III demonstrated an early induction for both male and female beetles, with transcripts being detectable after 45 min. An expression profile of male midgut tissue indicated Ipi10G08 transcript levels reach a maximum induction of ∼22.5-fold control levels at 4 h post-treatment. Tissue distribution studies displayed a large induction of Ipi10G08 mRNA in the alimentary canal of JH III-treated beetles, especially in males. A dose curve from both sexes suggested there may be a difference in the ability to respond to lower levels of JH III and immunoblot analysis indicated that although JH III highly induces transcript levels in females, protein levels are not similarly induced, while protein levels are induced in males. Ipi10G08 is likely a primary JH response gene and may provide insight into how this hormone exerts its actions.