The microRNA pathway core genes are indispensable for development and reproduction in the brown planthopper, Nilaparvata lugens

Abstract

MicroRNAs (miRNAs) are small single‐stranded non‐coding RNAs involved in a variety of cellular events by regulating gene expression at the post‐transcriptional level. Several core genes in miRNA biogenesis have been reported to participate in a wide range of physiological events, in some insect species. However, the functional significance of miRNA pathway core genes in Nilaparvata lugens remains unknown. In the present study, we conducted a systematic characterisation of five core genes involved in miRNA biogenesis. We first performed spatiotemporal expression analysis and found that miRNA core genes exhibited similar expression patterns, with high expression levels in eggs and relatively high transcriptional levels in the ovaries and fat bodies of females. RNA interference experiments showed that injecting third‐instar nymphs with dsRNAs targeting the miRNA core genes, NlAgo1, NlDicer1, and NlDrosha resulted in high mortality rates and various degrees of body melanism, moulting defects, and wing deformities. Further investigations revealed that the suppression of miRNA core genes severely impaired ovarian development and oocyte maturation, resulting in significantly reduced fecundity and disruption of intercellular spaces between follicle cells. Moreover, the expression profiles of miR‐34‐5p, miR‐275‐3p, miR‐317‐3p, miR‐14, Let‐7‐1, and miR‐2a‐3p were significantly altered in response to the knockdown of miRNA core genes mixture, suggesting that they play essential roles in regulating miRNA‐mediated gene expression. Therefore, our results provide a solid theoretical basis for the miRNA pathway in N. lugens and suggest that the NlAgo1, NlDicer1, and NlDrosha‐dependent miRNA core genes are essential for the development and reproduction of this agricultural pest.

Disruption of microRNA pathway core genes inhibits molting and reproduction of the cigarette beetle, Lasioderma serricorne

“…9 In N. lugens, silencing of NlDrosha, NlDicer1 and NlArgonaute-1 resulted in severe interruption of oocyte maturation and ovarian development, and significantly decreased fecundity. 40 The same phenomenon is also observed when silencing B. tabaci Dcr1 and Argonaute-1, S. furcifera SfDicer1, L. migratoria Argonaute-1 and B. dorsalis Argonaute-1. 10,15,42 Given that LsDicer-1 and LsArgonaute-1 are key components of the miRNA pathway, we speculated that they may play major roles in regulating ovarian development, and thus we used phenol fuchsin to stain the ovaries of the insects after silencing.…”

“…47 In N. lugens, silencing of NlDrosha, NlDicer1 and NlArgonaute-1 resulted in high mortality, wing deformities and molting defects. 40 In this study, the knockdown of LsDicer-1, LsArgonaute-1, LsDrosha and LsExportin-5 resulted in abnormal molting and significant mortality. Similar phenotypes, especially those reflecting an impact on wing development, have also been reported in other insects.…”

“…10 By contrast, Dicer-1, Argonaute-1, Pasha, Loquacious and Drosha were highly expressed in the egg stage of N. lugens and H. armigera, indicating that those genes might be involved in embryonic development and egg maturation. 40 In L. migratoria, Bactrocera dorsalis and B. mori, Argonaute-1 was predominantly expressed in the ovaries. 12,41,42 Similar results were obtained for LsArgonaute-1 of L. serricorne, indicating that Argonaute-1 participates in the development of insect ovaries.…”

“…38 Loquacious and Exportin-5 have the typical structures of their respective protein families, which are highly similar to the homologs of other insects. 39,40 LsArgonaute-1 is the key effect of miRNA function, which is characterized by DUF1785, PAZ and Piwi domains, showing high consistency and homology with the Locusta migratoria 12 and N. lugens 40 Argonaute-1 protein.…”

“…12,41,42 Similar results were obtained for LsArgonaute-1 of L. serricorne, indicating that Argonaute-1 participates in the development of insect ovaries. Some studies have shown that miRNA pathway genes are highly expressed in the testes, including Dicer1 in B. mori, 11 Loquacious in N. lugens 40 and Dicer1 in B. tabaci. 10 Furthermore, we found that LsDicer-1, LsPasha, LsDrosha and LsLoquacious had the highest expression levels in the integument, Malpighian tubules, foregut and midgut, respectively, highlighting their tissue-specific functions in L. serricorne.…”