Lse-novel_mir23 Directly Targets LsPI3K21B and Contributes to Pupal–Adult Metamorphosis in the Cigarette Beetle Lasioderma serricorne

The insulin/insulin-like signaling (IIS) pathway is central to insect growth and metamorphosis, yet its post-transcriptional regulation in stored-product insects remains poorly understood. Here, we investigated the function of LsPI3K21B and its potential regulation by microRNAs during the pupal–adult metamorphosis of the cigarette beetle, Lasioderma serricorne. Silencing LsPI3K21B via RNA interference resulted in severe developmental defects, reduced wing pigmentation and size, altered expression of chitin- and wing-related genes, and increased mortality. Three candidate miRNAs were predicted to target LsPI3K21B, of which Lse-novel_mir23 showed an inverse expression pattern and significantly affected LsPI3K21B transcript abundance following mimic or inhibitor treatment. Dual-luciferase assays demonstrated sequence-dependent repression through the LsPI3K21B 3′-UTR, and RNA pull-down assays verified the association of Lse-novel_mir23 with LsPI3K21B transcripts. Increased Lse-novel_mir23 activity phenocopied key developmental defects caused by LsPI3K21B depletion. These findings identify a previously uncharacterized miRNA-LsPI3K21B regulatory interaction associated with beetle metamorphosis and provide a molecular framework for targeting developmental regulators in RNA-based management strategies for L. serricorne.