Macadamia Volatiles Affect the Attraction of the Moth Gymnandrosoma Aurantianum to (E)-8-Dodecenyl Acetate the Main Component of its Sex Pheromone

The macadamia nut borer moth Gymnandrosoma aurantianum, is the main pest of macadamia (Macadamia integrifolia) in Central America. This study investigates the effect of the host (M. integrifolia) on attraction of G. aurantianum to its sex pheromone. Y-Tube bioassays showed that females G. aurantianum were attracted to volatiles from M. integrifolia leaves and flowers, while males responded to volatiles from flowers. Both sexes had significantly different electroantennographic responses (EAG) to the extracts of volatiles from flowers, fruits and leaves and (E)-8-dodecenyl acetate (main component of the sex pheromone of G. aurantianum). Females G. aurantianum exhibited electroantennographic responses by CG-EAD to phenylacetaldehyde, (1Z)-3-methylbutanal oxime and (E)-β-ocimene, while the males showed antennal activity in response to phenylacetaldehyde, (1E)-3-methylbutanal oxime, (1Z)-3-methylbutanal oxime, present in the extracts of M. integrifolia. The EAG dose-response with ocimene (mix of isomers) showed that female antennal activity increases as the dose increases, while with males, the highest dose elicited a response that was significantly different from the control. In field tests, the mixture (ocimene/(E)-8-dodecenyl acetate) with the proportion of 10:1 was the treatment that captured the highest number of males and females. Also, we observed that the lowest number of male captures was obtained with the proportion of 1:1, compared to the traps baited with only (E)-8-dodecenyl acetate. These results suggest that the binary mixture of ocimene plus (E)-8-dodecenyl acetate in a proportion of 10:1 could be an option for monitoring this pest because we obtained captures of both sexes.

Evolution of the Sex Pheromone Communication System in Ostrinia Moths

It remains a conundrum in the evolution of sexual communication how the signals and responses can co-ordinate the changes during speciation. The genus Ostrinia contains several closely related species as well as distinctive strains with pheromone polymorphism and represents an example of ongoing speciation. Extensive studies in the genus, especially in the species the European corn borer O. nubilalis (ECB), the Asian corn borer O. furnacalis (ACB) and the adzuki bean borer O. scapulalis (ABB), have provided valuable insights into the evolution of sex pheromone communication. This review presents a comprehensive overview of the research on pheromone communication in different Ostrinia species over the past four decades, including pheromone identification and biosynthesis, the ligand profiles of pheromone receptor (PR) genes, the physiology of peripheral olfactory sensory neurons (OSNs) and the projection pattern to the antennal lobe. By integrating and comparing the closely related Ostrinia species and strains, it provides an evolutionary perspective on the sex pheromone communication in moths in general and also outlines the outstanding questions that await to be elucidated by future studies.

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.