Fig. 3.

Interaction of miRNA and hormone pathways in insect metamorphosis. a Regulatory loops of miRNA and hormonal signaling cascades. In Drosophila, miR-14 downregulates EcR, and reciprocally 20E via EcR represses miR-14 expression, which forms a positive autoregulatory loop to amplify 20E signaling [107]. 20E, EcR and miR-965 also constitute a positive regulatory loop in a mutual repression circuit [108]. In addition, mutual repression between miR-281 and 20E-EcR was observed in Bombyx mori [109]. In Locusta migratoria, let-7 and miR-278 inhibit Kr-h1 expression, whereas let-7 and miR-278 are downregulated by JH, which work together to maintain an appropriate level of Kr-h1 in nymphs essential for preventing precocious metamorphosis [88]. b Experimentally confirmed miRNAs that are involved in 20E signaling pathway and regulate insect metamorphosis, represented by holometabolous D. melanogaster as well as hemimetabolous Nilaparvata lugens and L. migratoria