Identification of Δ9 and Δ11 Desaturases Involved in Sex Pheromone Biosynthesis in <i>Mythimna loreyi</i> (Lepidoptera: Noctuidae)

In moths, sex pheromones are synthesized in pheromone glands (PGs) by a variety of enzymes. Desaturases (DESs) are critical for the introduction of double bonds into pheromones. In <i>Mythimna loreyi</i>, the specific DESs involved in sex pheromone biosynthesis remain unclear. In this study, we identified and characterized 25 putative DESs from the <i>M. loreyi</i> genome. Nineteen of them were expressed in the female PGs, with seven showing significant upregulation in response to pheromone biosynthesis activating neuropeptide (PBAN). RNAi-based knockdown of <i>MlorDES2</i> significantly reduced the titer of pheromone components by 58.6-85.9%, while knockdown of <i>MlorDES9</i> specifically reduced the production of (<i>Z</i>)-9-tetradecenyl acetate. Functional verification in yeast revealed that MlorDES2 and MlorDES9 exhibited Δ11 and Δ9 desaturase activities, respectively. Taken together, these results collectively demonstrate that MlorDES2 and MlorDES9 are involved in sex pheromone biosynthesis of <i>M. loreyi</i>, suggesting that DESs could be used as potential targets for pest management.