Conserved microRNAs miR-8-3p and miR-2a-3 targeting chitin biosynthesis to regulate the molting process of Sogatella furcifera (Horváth)(Hemiptera: Delphacidae)

Molting is a key solution to growth restriction in insects. The periodic synthesis and degradation of chitin, one of the major components of the insect epidermis, is necessary for insect growth. MicroRNA (miRNA) have been implicated in molting regulation, yet their involvement in the interplay interaction between the chitin synthesis pathway and 20-hydroxyecdysone signaling remains poorly understood. In this study, soluble trehalase (Tre1) and phosphoacetylglucosamine mutase (PAGM) were identified as targets of conserved miR-8-3p and miR-2a-3, respectively. The expression profiles of miR-8-3p-SfTre1 and miR-2a-3-SfPAGM exhibited an opposite pattern during the different developmental stages, indicating a negative regulatory relationship between them. This relationship was confirmed by an in vitro dual-luciferase reporter system. Overexpression of miR-8-3p and miR-2a-3 by injection of mimics inhibited the expression of their respective target genes and increased mortality, leading to death in the pre-molting, and molting death phenomena. They also caused a decrease in chitin content and expression levels of key genes in the chitin synthesis pathway (SfTre1, SfTre2, SfHK, SfG6PI, SfGFAT, SfGNA, SfPAGM, SfUAP, SfCHS1, SfCHS1a, and SfCHS1b). Conversely, the injection of miRNA inhibitors resulted in the upregulation of the expression levels of these genes. Following 20E treatment, the expression levels of miR-8-3p and miR-2a-3 decreased significantly, while their corresponding target genes increased significantly. These results indicate that miR-8-3p and miR-2a-3 play a regulatory role in the molting of Sogatella furcifera by targeting SfTre1 and SfPAGM, respectively. These findings provide new potential targets for the development of subsequent new control strategies.