MicroRNAs miR-14 and miR-2766 regulate tyrosine hydroxylase to control larval–pupal metamorphosis in Helicoverpa armigera

BACKGROUND: The cotton bollworm, Helicoverpa armigera, is a worldwide polyphagous pest, causing huge economic losses in vegetable, cotton and corn crops, among others. Owing to long-term exposure to Bacillus thuringiensis (Bt) toxins, evolution of resistance has been detected in this pest. As a conservative and effective neurotransmitter, dopamine (DA) has an important role in insect growth and development. In this study, we investigated the regulatory functions of DA and its associated non-coding RNA in metamorphosis in H. armigera. RESULTS: Expression profiles indicated that DA and DA pathway genes were highly expressed during larval–pupal metamorphosis in H. armigera. RNA interference and pharmacological experiments confirmed that tyrosine hydroxylase (TH), dopa decarboxylase, vesicular amine transporter and DA receptor 2 are critical genes related to the development of H. armigera from larvae to pupae. We also found that miR-14 and miR-2766 targeted the 3′ untranslated region to post-transcriptionally regulate HaTH function. Application of miR-2766 and miR-14 antagomirs significantly increased levels of HaTH transcripts and proteins, while injection of miR-2766 and miR-14 agomirs not only suppressed messenger RNA and protein levels of HaTH, but also resulted in defective pupation in H. armigera. CONCLUSION: These results suggest that DA deficiency inhibits larval–pupal metamorphosis in H. armigera. Potentially, DA pathway genes and their microRNAs could be used as a novel target for H. armigera management.