Discrimination between Enantiomers of Linalool by Olfactory Receptor Neurons in the Cabbage Moth Mamestra brassicae (L.)

Abstract

Plants emit complex blends of volatiles, including chiral compounds that might be detected by vertebrates and invertebrates. Insects are ideal model organisms for studying the underlying receptor neuron mechanisms involved in olfactory discrimination of enantiomers. In the present study, we have employed two-column gas chromatography linked to recordings from single olfactory receptor neurons of Mamestra brassicae, in which separation of volatiles in a polar and a chiral column was performed. We here present the response properties of olfactory receptor neurons tuned to linalool. The narrow tuning of these receptor neurons was demonstrated by their strong responses to (R)-(-)-linalool, the weaker responses to the (+)-enantiomer as well as a few structurally related compounds, and no responses to the other numerous plant released volatiles. The enantioselectivity was verified by parallel dose-response curves, that of (R)-(-)-linalool shifted 1 log unit to the left of the (S)-(+)-linalool curve. A complete overlap of the temporal response pattern was found when comparing the responses of the same strength. Analysis of the spike amplitude and waveform indicated that the responses to the two enantiomers originated from the same neuron.

Electrophysiological responses of four fungivorous coleoptera to volatiles of Trametes versicolor: implications for host selection

“…In other bracket fungi species the R:S ratios range from a minimum of 89% to a maximum of 98% of the (R)-enantiomer (Ziegenbein et al 2006). Although an enantiomeric discrimination was observed in several insect species (Ulland et al 2006) previous analysis with C. boleti revealed no significant differences in responses to either enantiomer in EAG. In behavioural tests the females showed a preference for the (S)-enantiomer (Thakoew et al 2008: Fig.…”

Behavioral insensitivity to DEET in Aedes aegypti is a genetically determined trait residing in changes in sensillum function

“…If, as suggested by Syed and Leal (12), DEET is being recognized by a neuron that naturally responds to plant compounds, it is possible that the alteration in the i line that leads to lowered recognition of DEET may also affect the response to the plant-derived compound (AE)-linalool. Linalool enantiomers are present in the essential oils of different plants and have distinct scents that insects can differentiate between (28) or that can be detected at different thresholds (29). The ability to detect the enantiomers separately may serve a purpose in the ecology of the insect.…”

More lessons from linalool: insights gained from a ubiquitous floral volatile

“…Recent studies have documented female-specific responses to (S)-(+)-linalool in the silk moth Bombyx mori [36] and enantio-specific responses (greater sensitivity to (R)-(À)-linalool) in the noctuid moth Mamestra brassicae [37], moths whose phylogenetic and ecological affinities differ markedly from those of M. sexta. These findings, along with the homologous nature of the olfactory receptor neurons that selectively respond to linalool [38], suggest a much broader relevance for this plant volatile and the selective pressures driving its perception by insect herbivores.…”