Biosynthetic pathway and mating-regulated synthesis of 2-(undecyloxy)-ethanol in Monochamus saltuarius: Implications for pheromone-mediated communication and pest management.

Pine wilt disease (PWD), caused by the pine wood nematode (PWN, Bursaphelenchus xylophilus), poses a severe threat to pine forests worldwide. In northeastern China, Monochamus saltuarius (Coleoptera: Cerambycidae) is a primary vector of this disease. The male-produced aggregation pheromone 2-undecyloxy-1-ethanol plays a critical role in mating and reproductive behavior across several Monochamus species. Understanding its biosynthesis can reveal key targets for pheromone disruption, providing a foundation for pest management. In this study, we investigated the site, temporal dynamics, and regulatory mechanisms of 2-undecyloxy-1-ethanol biosynthesis in male M. saltuarius through morphological observation, pheromone release profiling, multi-omics analyses and RNA interference. Our results identified the prothorax as the primary site of pheromone biosynthesis, with pheromone levels displaying an "M-shaped" pattern during sexual maturation and post-mating stages. We identified 118 candidate genes associated with pheromone biosynthesis and three key pathways involved in the process. Notably, silencing two SDR genes significantly reduced pheromone titers and weakened female antennal responses to cuticular extracts from dsRNA-treated males. These findings provide molecular insights into pheromone biosynthesis and indicate that SDRs may be potential targets for RNAi-based disruption, offering an environmentally friendly approach for controlling M. saltuarius and mitigating PWD.