Gut bacteria-mediated regulation of pheromone synthesis in Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) via TcFAS1 modulation

Our previous research has revealed that gut bacteria enhance male attractiveness to females by promoting pheromone 4,8-dimethyldecanal (4,8-DMD) production in Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). However, its underlying mechanism remains largely unknown. Symbionts influence insect pheromone synthesis in both direct and indirect manners. Since the sites of 4,8-DMD synthesis are located far from the gut, and spatial remoteness precludes direct pheromone synthesis by gut bacteria. Therefore, this study hypothesizes that gut bacteria regulate pheromone synthesis of T. castaneum by modulating the expression of related genes. To verify this hypothesis, axenic and gnotobiotic male beetles were established, and Escherichia coli, a key gut bacterium essential for growth and development of T. castaneum, was selected as the target symbiont. Further, transcriptome analysis was performed to examine the effect of E. coli on the expression levels of genes related to pheromone synthesis in T. castaneum and the fatty acid synthesis gene was identified as the target gene. Knockdown of TcFAS1 resulted in a reduction of 4,8-DMD production in E. coli-gnotobiotic male beetles. These results suggest that E. coli regulates pheromone synthesis of T. castaneum by mediating the expression of TcFAS1. It is the first time to investigate symbiont-induced pheromone biosynthesis in T. castaneum, and provides a novel strategy for pest management by utilizing antibiotics or RNA interference techniques to disrupt insect mating communication and to control pest populations.