Comparative transcriptome analysis of sex pheromone glands of two sympatric lepidopteran congener species

• Two sympatric congener species share major sex pheromone (SP) components.
• Comparative transcriptome analysis of SP glands predicts the biosynthesis pathway of SP components.
• The variation of SP composition can be explained by sequence variations of FAR and desaturase genes.

Two internal apple feeders of Grapholita molesta and Grapholita dimorpha share two major sex pheromone components (stereoisomers) and exhibit a similar circadian rhythm of mating behavior. This study aimed to determine the genetic factors diversifying these two congeners with respect to sex pheromone biosynthetic machinery. Transcriptomes of sex pheromone glands in both species were analyzed with a deep sequencing technology. To find out the gene(s) responsible for the stereoisomer ratios of G. molesta and G. dimorpha, a hypothetic sex pheromone biosynthetic pathway was predicted based on the transcriptomes of their sex pheromone glands. Some orthologs of Δ10 desaturase and FARs in the synthetic pathway were specifically expressed in sex pheromone glands. The relatively high variation in DNA sequence and expression levels between G. molesta and G. dimorpha suggest their crucial roles in generating differential ratios of the sex pheromone stereoisomers in these two sympatric congeners.