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. © 2022 Society of Chemical Industry.

MicroRNA-277 regulates dopa decarboxylase to control larval-pupal and pupal-adult metamorphosis of Helicoverpa armigera

Insect metamorphosis is a complex process involving many metabolic pathways, such as juvenile hormones and molting hormones, bioamines, microRNAs (miRNAs), etc. However, relatively little is known about the biogenic amines and their miRNAs to regulate cotton bollworm metamorphosis. Here we show that one miRNA, miR-277 regulates larval-pupal and pupal-adult metamorphosis of cotton bollworm by targeting the 3'UTR of Dopa decarboxylase (DDC), a synthetic catalytic enzyme of dopamine. Injection of miR-277 agomir inhibited the expression of DDC at the mRNA and protein levels, leading to defects in the pupation and emergence of H. armigera that was consistent with the phenotype obtained by injection of DDC double-stranded RNA (dsRNA). Injection of miR-277 antagomir induced the mRNA and protein expression of DDC and rescued the phenotype of pupation failure caused by DDC gene silencing. Unexpectedly, miR-277 antagomir can also cause failure of emergence of H. armigera and both agomir and antagomir of miR-277 injection could cause abnormal phenotypes in wing veins. This study reveals that elaborate regulation of miRNA and its target gene expression is prerequisite for insect development, which provides a new insight to study the developmental mechanisms of insect wing veins.

Genomics of ecological adaptation in cactophilic Drosophila

Cactophilic Drosophila species provide a valuable model to study gene–environment interactions and ecological adaptation. Drosophila buzzatii and Drosophila mojavensis are two cactophilic species that belong to the repleta group, but have very different geographical distributions and primary host plants. To investigate the genomic basis of ecological adaptation, we sequenced the genome and developmental transcriptome of D. buzzatii and compared its gene content with that of D. mojavensis and two other noncactophilic Drosophila species in the same subgenus. The newly sequenced D. buzzatii genome (161.5 Mb) comprises 826 scaffolds (>3 kb) and contains 13,657 annotated protein-coding genes. Using RNA sequencing data of five life-stages we found expression of 15,026 genes, 80% protein-coding genes, and 20% noncoding RNA genes. In total, we detected 1,294 genes putatively under positive selection. Interestingly, among genes under positive selection in the D. mojavensis lineage, there is an excess of genes involved in metabolism of heterocyclic compounds that are abundant in Stenocereus cacti and toxic to nonresident Drosophila species. We found 117 orphan genes in the shared D. buzzatii–D. mojavensis lineage. In addition, gene duplication analysis identified lineage-specific expanded families with functional annotations associated with proteolysis, zinc ion binding, chitin binding, sensory perception, ethanol tolerance, immunity, physiology, and reproduction. In summary, we identified genetic signatures of adaptation in the shared D. buzzatii–D. mojavensis lineage, and in the two separate D. buzzatii and D. mojavensis lineages. Many of the novel lineage-specific genomic features are promising candidates for explaining the adaptation of these species to their distinct ecological niches.