The regulation of Δ11-desaturase gene expression in the pheromone gland of Mamestra brassicae (Lepidoptera; Noctuidae) during pheromonogenesis

Abstract

Cabbage moth (Mamestra brassicae) females produce sex pheromones to attract conspecific males. In our M. brassicae colony, the pheromone blend is composed of Z11-hexadecenyl acetate (Z11-16Ac) and hexadecyl acetate (16Ac) in a 93:7 ratio. A fatty acyl Δ11-desaturase is involved in the production of the main pheromone component. The release of Pheromone Biosynthesis Activating Neuropeptide (PBAN) regulates the pheromone production in the pheromone gland (PG).We cloned a cDNA encoding the MambrΔ11-desaturase and analyzed its expression profile over time in M. brassicae tissues. Transcript levels of the Δ11-desaturase in larvae, pupal PGs, fat body, brain and muscle tissues were <0.1% of that in female PGs, whereas expression in male genitalia was 2%. In the PGs of virgin females the expression level increased continuously from eclosion to the end of the 1st day when it reached a plateau without further significant fluctuation up to the 8th day. In contrast, we recorded a characteristic daily rhythmicity in pheromone production with a maximum around 200ng Z11-16Ac/PG. In some experiments, females were decapitated to prevent PBAN release and thereby inhibit pheromone production, which remarkably increased after treatment with Mambr-Pheromonotropin. Further experiments revealed that mating resulted in a significant suppression of pheromone production. However, expression of the Δ11-desaturase was not affected by any of these interventions, suggesting that it’s not regulated by PBAN. Fluorescent microscopy was used to study the potential role of lipid droplets during pheromone production, however, no lipid droplets were identified indicating that pheromonogenesis is regulated via de novo fatty acid synthesis.