Exploring the Terminal Pathway of Sex Pheromone Biosynthesis and Metabolism in the Silkworm

Sex pheromones are vital to sexual communication and reproduction in insects. Although some key enzymes in pheromone production have been well studied, information on genes involved in the terminal pathway is limited. The domestic silkworm employs a pheromone blend containing (E,Z)-10,12-hexadecadienol (bombykol) and analogous (E,Z)-10,12-hexadecadienal (bombykal); whereas, its wild ancestor B. mandarina uses only bombykol. The two closely related moths might be a good model for exploring the genes involved in aldehyde pheromone synthesis and metabolism. By deep sequencing and analyzing the sex pheromone gland (PG) transcriptomes; we identified 116 candidate genes that may be related to pheromone biosynthesis, metabolism, and chemoreception. Spatiotemporal expression profiles and differentially expressed analysis revealed that four alcohol oxidases (BmorAO1; 2; 3; and 4); one aldehyde reductase (BmorAR1); and one aldehyde oxidase (BmorAOX5) might be involved in the terminal pathway. Phylogenetic analysis showed that, except for BmorAO3 and MsexAO3, AOs did not show a conversed orthologous relationship among moths; whereas, ARs and AOXs were phylogenetically conserved. This study provides crucial candidates for further functional elucidation, and which may be utilized as potential targets to disrupt sexual communication in other moth pests.

Transcriptome analysis of the sex pheromone gland and pheromone biosynthetic pathway in Eogystia hippophaecolus

The moth Eogystia hippophaecolus (Hua et al.) is a major threat to sea buckthorn plantations in China. Specific and highly efficient artificial sex pheromone traps have been developed and used to control this pest species. However, the biosynthesis of sex pheromones Z7-14:Ac and E3-14:Ac remains poorly understood.Results We investigated the female pheromone gland transcriptome of E. hippophaecolus and identified two pheromone biosynthesis-activating neuropeptides (PBANs), two pheromone biosynthesis-activating neuropeptide receptors (PBANrs), five acetyl-CoA carboxylases (ACCs), six fatty acid synthases (FASs), 16 Acyl-CoA desaturases (DESs), 26 reductases (REDs), 13 acetyltransferases (ACTs), one fatty acid transport protein (FATP), one acyl-CoA-binding protein (ACBP), and five elongation of very long-chain fatty acid proteins (ELOs) in pheromone biosynthesis pathways. Additionally, we identified 11 odorant-degrading enzymes (ODEs) and 16 odorant-binding proteins (OBPs), 14 chemosensory proteins (CSPs), two sensory neuron membrane proteins (SNMPs), three odorant receptors (ORs), seven ionotropic receptors (IRs), and six gustatory receptors (GRs).Conclusions 77 unigenes involved in female pheromone biosynthesis, 31 chemoreception proteins and 11 odorant degradation enzymes were identified, which provided insight into the regulation of the pheromone components and pheromone recognition in the sex gland, and knowledge pertinent to new integrated pest management strategy of interference pheromone biosynthesis and recognition.