Abstract
Moths use their sense of smell to find food sources, mating partners and oviposition sites. For this they possess a family of odorant receptors (ORs). Some ORs are used by both sexes whereas others have sex-specific roles. For example, male moths possess ORs specifically tuned to sex pheromones produced by conspecific females. Here we identify sets of ORs from the antennae of New Zealand endemic leafroller moths Planotortrix octo (48 ORs) and P. excessana (47 ORs) using an RNA-Seq approach. Two orthologous ORs show male-biased expression in the adult antennae of both species (OR7 and OR30) and one other OR in each species was female-biased in its expression (PoctOR25, PexcOR14) by qPCR. PAML analysis conducted on male-biased ORs indicated positive selection acting on the male-biased OR7. The fact that OR7 is likely under positive selection, that it is male-biased in its expression and that its orthologue in C. obliquana, CoblOR7, responds to sex pheromone components also utilised by Planotortrix species, suggests that this receptor may also be important in sex pheromone reception in Planotortrix species.
Highlights
In the insect world chemical cues play an important role in orientation and communication
A comparison with odorant receptors (ORs) identified in species of the sister genus Ctenopseustis, C. obliquana and C. herana [30], revealed that OR60 is exclusively expressed in antennae of P. octo and P. excessana and OR11 is found in C. obliquana and C. herana antennae only
The clade containing sex pheromone receptors from other moth species including C. obliquana and C. herana is supported by bootstrap analysis (81% from 1000 bootstrap replicates)
Summary
In the insect world chemical cues play an important role in orientation and communication. For example, use their sense of smell to locate food, oviposition sites and mates [1,2]. For this they use an array of odorant receptors (ORs) located in sensilla that are found mainly on the insect’s antennae. Male moths use specialised ORs to locate conspecific females by tracking sex pheromones produced by specialised glands in the terminal segment of the female abdomen [3]. It is important to be able to discriminate between compounds produced by conspecific or hetero-specific females because mating mistakes are costly in terms of reproduction and can be fatal for both individuals [2]
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