Alkaline–Acid Intestine Environment Controlled by A Carbonic Anhydrase Gene Influences Synthesis of Sex Pheromone by Symbionts

The intricate interplay between animals and their intestinal microbes is pivotal in shaping various aspects of animal biology. However, the degree to which hosts can modulate the activity of their intestinal microbes, as well as the underlying molecular mechanisms, remains poorly elucidated. The production of sex pheromones by rectal Bacillus in male Bactrocera dorsalis is triggered by the alkaline intestine environment. An experimental increase in pH lead to more sex pheromone production, or vice versa. pH modulates the synthesis quantity of sex pheromone by exerting an impact on the activity of enzyme synthesizing sex pheromone in Bacillus. Transcriptome analysis shows that a highly expressed carbonic anhydrase (CAh) gene in B. dorsalis is associated with alkaline rectal environment. CAh inhibitor feeding and RNAi targeting the CAh gene lead to a shift from alkaline to acidic conditions within rectum and subsequent decreasing in sex pheromone synthesis and mating. This study provides novel insight into the influence of intestinal environment on intestinal microbes and has significant implication for understanding the molecular mechanism underlying sex pheromone synthesis by symbionts in insects.