MicroRNA Let‐7 targets the ecdysone signaling pathway E75 gene to control larval–pupal development in Bactrocera dorsalis

Abstract MicroRNAs (miRNAs) regulate various biological processes during insect development; however, their role in larval–pupal development in oriental fruit fly, Bactrocera dorsalis (Hendel) remains unknown. In the current study, we address the biological function of a conserved miRNA, Bdo‐Let‐7 in the regulation of BdE75 gene, which belongs to the ecdysone signaling pathway and participates in the larval–pupal development in B. dorsalis . Using dual luciferase reporter assay in HEK293T cells we show that Bdo‐Let‐7 miRNA interacts with the 3′ untranslated region of BdE75 gene and suppresses its expression. The Bdo‐Let‐7 and BdE75 are also co‐expressed in the larval–pupal stages and in different tissues of B. dorsalis . In in vivo experiments, the injection of Bdo‐Let‐7 agomir and antagomir in third instar larvae down‐ and up‐regulated the expression of BdE75 , respectively. The 20‐hydroxyecdysone (20E) injection assay shows that 20E up‐regulated the expression of Bdo‐Let‐7 on the 5th day of the larvae. Moreover, abnormal pupation and eclosion were observed after larval Bdo‐Let‐7 antagomir injection. Based on these results, we show that Bdo‐Let‐7 regulates the ecdysone signaling pathway through the exact dose of BdE75 gene, and is indispensable for normal larval–pupal development in B. dorsalis .