Molecular mechanisms of <i>s</i>-methoprene-induced growth inhibition in <i>Ephestia elutella</i> (Hübner) (Lepidoptera: Pyralidae): insights from transcriptomic analysis

Ephestia elutella is a globally distributed storage pest, and its growth and development are regulated by juvenile hormones. To investigate the molecular mechanisms underlying the response of E. elutella larvae to the juvenile hormone analog s-methoprene, this study examined the effects of s-methoprene on the growth and development of E. elutella, explored the response of E. elutella to s-methoprene exposure by transcriptomic analysis, and confirmed its hub genes by RT-qPCR experiments. Larval mortality of E. elutella increased and adult emergence decreased with increasing exposure durations and doses of s-methoprene. After exposure at 5 × 10⁻⁵ mg/cm² of s-methoprene for 4 wk, a few of larvae pupated, but failed to emerge into adults, while at 50 × 10⁻⁵ mg/cm² for 4 wk, larvae were completely unable to pupate. Transcriptomic analysis identified 2,569 and 6,719 differentially expressed genes in the EE0 vs. EE5 and EE0 vs. EE50, respectively. Weighted Gene Co-expression Network Analysis identified 5 modules, with the yellow module most relevant to EE5. The genes in the yellow module were significantly enriched in biological processes. The Cluster-6182.18691, Cluster-6182.8343, Cluster-6182.28346, and Cluster-6182.21392 were hub genes in the yellow module. s-Methoprene directly or indirectly inhibited the growth and development of E. elutella larvae by affecting critical biological processes, such as hormonal regulation, etc. RT-qPCR validation confirmed the reliability of the transcriptomic data. This study provides important foundational data and theoretical insights into the molecular mechanisms of E. elutella in response to s-methoprene.