miR-318 regulates juvenile hormone biosynthesis to control ovarian development in Bactrocera dorsalis.

Reproduction is a fundamental process in the insect life cycle, with the ovary serving as the central organ governing oogenesis and fertility. Hormonal homeostasis, particularly juvenile hormone (JH) regulation, is critical for proper ovarian development. Bactrocera dorsalis (Hendel) is a globally invasive agricultural insect pest characterized by high reproductive capacity. MicroRNAs (miRNAs) are key post-transcriptional regulators of diverse biological processes, yet their roles in insect ovarian development remain incompletely understood. Here, we identify miR-318 as an ovary-enriched miRNA that regulates reproduction in B. dorsalis. Overexpression of miR-318 via mimic injection impairs ovarian development, reduces fecundity, and decreases egg hatchability, whereas CRISPR/Cas9-mediated knockout of miR-318 produces similar reproductive defects. Bioinformatic prediction and molecular assays reveal that miR-318 directly targets farnesol dehydrogenase (FolDH), an essential enzyme in the JH biosynthesis pathway, thereby modulating JH titers and female fertility. These findings establish a miR-318/FolDH regulatory axis upstream of JH that controls ovarian development and provide mechanistic insight into miRNA-mediated regulation of insect reproduction. Importantly, this work highlights the potential of miRNAs as upstream modulators of hormone biosynthesis and as targets for species-specific management of cyclorrhaphan dipteran pests.